Chemical context   {#sec1}
==================

Over the past few decades, organo­sulfonate and organo­carboxyl­ate anions have become popular building blocks for metal-organic framework (MOF) structures (Dey *et al.*, 2014[@bb5]; Shimizu *et al.*, 2009[@bb20]; Cai, 2004[@bb2]). Having previously investigated some structures of the bifunctional 4-sulfo­benzoic acid anion (Gunderman & Squattrito, 1994[@bb6]), we recently decided to examine its inter­actions with some softer (and therefore sulfophilic) late transition metals. Reactions with Cu^2+^ and Ag^+^ were carried out that resulted in four new structures that are described herein.

Structural commentary   {#sec2}
=======================

The aqueous reaction of copper(II) carbonate, potassium 4-sulfo­benzoic acid, and hydro­chloric acid produced two copper-containing products. Blue parallelepiped-shaped crystals were found to have the formula \[Cu(H~2~O)~4~(O~3~SC~6~H~4~CO~2~H)~2~\]·2H~2~O, (I)[](#scheme1){ref-type="chem"}. The structure finds the Cu^2+^ ions on centers of inversion with four closely bound water mol­ecules \[Cu---O distances of 1.9520 (7) and 1.9743 (7) Å\] in a square plane \[O6---Cu1---O7 angle of 90.38 (3)°\] (Fig. 1[▸](#fig1){ref-type="fig"}). Two sulfonate O atoms at 2.3934 (8) Å occupy the apical positions to complete a classic Jahn--Teller-distorted octa­hedral coordination of the copper ion. This type of bis­(sulfanato)copper(II) complex with the sulfonate ligands in the more distant apical position has been reported by Cai *et al.* (2001[@bb3]) with Cu---O distances *ca* 0.1--0.4 Å longer than the Cu1---O4 distance in (I)[](#scheme1){ref-type="chem"}. A comparable Cu---O sulfonate distance of 2.420 (2) Å is seen in bis­(4-amino­benzene­sulfonato)­diaqua­copper(II) (Gunderman *et al.*, 1996[@bb7]). The second product of the reaction, blue needles, was determined to be \[Cu(H~2~O)~6~\](O~3~SC~6~H~4~CO~2~H)~2~, (II)[](#scheme1){ref-type="chem"}, a structural isomer of (I)[](#scheme1){ref-type="chem"}. The copper ions in (II)[](#scheme1){ref-type="chem"} are also centrosymmetric and Jahn--Teller distorted with four close \[Cu---O distances of 1.941 (3) and 1.953 (3) Å\] and two more distant \[Cu---O = 2.515 (3) Å\] water mol­ecules in an otherwise very regular octa­hedral geometry (Fig. 2[▸](#fig2){ref-type="fig"}). As in (I)[](#scheme1){ref-type="chem"}, the carboxyl­ate group is protonated and does not have any direct metal--oxygen inter­actions. The lack of metal--sulfonate bonding is more typical of the behavior of other 3*d*-block divalent transition metals (Leonard *et al.*, 1999[@bb11]).

The reaction of silver nitrate and potassium 4-sulfo­benzoic acid yielded two silver-containing crystalline products reported here. Colorless needle-shaped crystals were identified as Ag~0.69~K~0.31~(O~3~SC~6~H~4~CO~2~H), (III)[](#scheme1){ref-type="chem"}, an anhydrous mixed silver/potassium salt of 4-sulfo­benzoic acid. The asymmetric unit (Fig. 3[▸](#fig3){ref-type="fig"}) contains two independent cation sites, both on twofold symmetry special positions of the space group *C*2/*c*. One site (Ag1) was judged to be fully occupied by Ag^+^ cations, while the other site consists of split positions *ca* 0.2 Å apart. This site was modeled as two positions (Ag2 and K2) with partial occupancies fixed at 38% and 62%, respectively. The overall composition of the data crystal is 69% Ag and 31% K, which was corroborated by energy dispersive X-ray (EDX) analysis. Ag1 is coordinated by six sulfonate O atoms at distances ranging from 2.4919 (11) to 2.5061 (10) Å in a moderately distorted octa­hedral geometry. Ag2 and K2 are also in a distorted octa­hedral environment formed from four sulfonate and two carboxyl­ate O atoms at distances of 2.470 (3)--2.751 (3) Å (Ag2) and 2.584 (6)--2.653 (2) Å (K2). The Ag---O distances are consistent with those seen in other silver arene­sulfonates (Côté & Shimizu, 2004[@bb4]), while the K---O distances are slightly shorter than those seen in three polymorphs of potassium 4-sulfo­benzoic acid (Kariuki & Jones, 1995[@bb8]), which are mostly between *ca* 2.65 and 2.95 Å. The extensive metal--sulfonate bonding is as expected given the softer nature of Ag^+^ and K^+^ relative to divalent 3*d* transition metal ions (Parr & Pearson, 1983[@bb14]). As in (I)[](#scheme1){ref-type="chem"} and (II)[](#scheme1){ref-type="chem"}, the carboxyl­ate group remains protonated with the acidic H atom unambiguously located on O1.

The second product of the silver reaction crystallizes as colorless hexa­gonal plates determined to be Ag~0.20~K~0.80~(O~3~SC~6~H~4~CO~2~H)·2H~2~O, (IV)[](#scheme1){ref-type="chem"}. This compound is isostructural with K(O~3~SC~6~H~4~CO~2~H)·2H~2~O, one of the polymorphs of the starting material potassium 4-sulfo­benzoic acid whose structure has been reported (Gunderman & Squattrito, 1994[@bb6]; Kariuki & Jones, 1995[@bb8]). The unique cation site was modeled as disordered with Ag^+^ and K^+^ present at occupancies fixed at 20% and 80%, respectively. This composition is supported by EDX analysis of the data crystal. The cation is surrounded by eight O atoms, including three water mol­ecules and five sulfonate O atoms (Fig. 4[▸](#fig4){ref-type="fig"}). Although Shannon (1976[@bb15]) assigns Ag^+^ a smaller radius than K^+^, they are within 15--20% of each other for coordination number 8 so occupancy of the same site seems reasonable. The K1/Ag1-O~water~ distances \[2.6233 (12), 2.7045 (13) and 2.8017 (11) Å\] are *ca* 0.09 Å shorter than those reported for the site fully occupied by K^+^, however, both determinations of the latter used room temperature data so the difference cannot be directly attributed to the smaller radius of the Ag^+^ ion. The tendency of potassium and silver to occupy the same or similar sites in the arene sulfonate/carboxyl­ate structures observed in this study is not the rule. For example, in silver potassium 5-sulfosalicylic acid, the Ag^+^and K^+^ ions occupy separate sites in the structure with very different coordination environments and no indication of mixed-occupancy (Li *et al.*, 2006[@bb12]).

Supra­molecular features   {#sec3}
==========================

The complexes in (I)[](#scheme1){ref-type="chem"} pack so as to create distinct layers of copper ions in the *ab* plane that alternate with layers of 4-sulfo­benzoic acid anions stacking in the *c*-axis direction (Fig. 5[▸](#fig5){ref-type="fig"}). This two-dimensional alternating inorganic--organic motif is typical of metal arene­sulfonates reported by us (Gunderman *et al.*, 1996[@bb7]; Leonard *et al.*, 1999[@bb11]) and others (Cai, 2004[@bb2]). The carboxyl­ate group remains protonated with the H atom clearly located on atom O1 and the CO~2~H moieties are situated within the organic layer with no direct inter­action with the cations. An extensive network of strong, nearly linear O---H⋯O hydrogen bonds (Table 1[▸](#table1){ref-type="table"}) involving the carb­oxy­lic H atom, coordinated water mol­ecules, unprotonated sulfonate and carboxyl­ate O atoms, and a non-coordinated water mol­ecule reinforce the packing. A portion of this network is shown in more detail in Fig. 6[▸](#fig6){ref-type="fig"}.

The packing pattern in (II)[](#scheme1){ref-type="chem"} is very similar to that in (I)[](#scheme1){ref-type="chem"} with layers of hexa­aqua­copper(II) cations in the *ab* plane alternating with layers of 4-sulfo­benzoic acid anions along the *c*-axis direction (Fig. 7[▸](#fig7){ref-type="fig"}). The anions are positioned with the sulfonate groups on the exterior of the layer and the carb­oxy­lic acid groups somewhat more to the inter­ior. All of the oxygen-bound H atoms participate in strong approximately linear O---H⋯O hydrogen bonds to the unprotonated sulfonate and carboxyl­ate O atoms or in the case of the carb­oxy­lic H atom to a coordinated water O atom (Table 2[▸](#table2){ref-type="table"}).

Given the highly acidic conditions of the reaction, it is not surprising that the less acidic carboxyl­ate proton is present in both products, effectively preventing the carboxyl­ate group from bonding directly to the copper ions. This outcome is undesirable from the standpoint of using the difunctional anion as a building block to make more extended metal--organic frameworks. Studies by other workers have shown that the use of hydro­thermal conditions at higher pH can be an effective route to novel structures of aromatic sulfonate/carboxyl­ate anions with coordination by both groups (Sun *et al.*, 2004[@bb21]). Other studies have successfully produced the desired framework structures without the need for hydro­thermal methods (Kurc *et al.*, 2012[@bb10]).

The packing in (III)[](#scheme1){ref-type="chem"} features layers of metal ions in the *bc* plane alternating with layers of 4-sulfo­benzoic acid anions stacking along the *a*-axis direction (Fig. 8[▸](#fig8){ref-type="fig"}). Anions in adjacent layers are linked in part by O---H⋯O hydrogen bonds between neighboring carb­oxy­lic acid groups in the classic dimerization of such mol­ecules (Table 3[▸](#table3){ref-type="table"}). Since both functional groups are involved in metal bonding, the anions are positioned with both groups equally exterior with respect to the layer, in contrast to the slipped arrangement in (I)[](#scheme1){ref-type="chem"} and (II)[](#scheme1){ref-type="chem"}.

As in the other structures reported here, the carb­oxy­lic acid in (IV)[](#scheme1){ref-type="chem"} is protonated and as in (I)[](#scheme1){ref-type="chem"} and (II)[](#scheme1){ref-type="chem"}, it is in a more inter­ior position in the anion layer than is the sulfonate group (Fig. 9[▸](#fig9){ref-type="fig"}). Once again, all of the oxygen-bound H atoms participate in a robust O---H⋯O network of hydrogen bonds detailed in Table 4[▸](#table4){ref-type="table"}.

Synthesis and crystallization   {#sec4}
===============================

The reaction that produced (I)[](#scheme1){ref-type="chem"} and (II)[](#scheme1){ref-type="chem"} was commenced by dissolving 2.085 g (8.68 mmol) of potassium 4-sulfo­benzoic acid (Aldrich, 98%) in 60 ml of water with gentle heating and stirring. To this solution was added 1.053 g (8.52 mmol) CuCO~3~ (Fisher), creating a thick green opaque mixture, followed by 50 drops of 12 *M* HCl. The solid gradually dissolved over *ca* 3 h leaving a clear light-blue solution that was then transferred to a porcelain evaporating dish and set out in a fume hood. Five days later, the water had completely evaporated, leaving behind large qu­anti­ties of three types of crystals: large colorless to slightly yellow plates, light-blue needles, and small blue parallelepipeds. The colorless plates were identified to be potassium 4-sulfo­benzoic acid dihydrate, the structure of which has been reported (Gunderman & Squattrito, 1994[@bb6]; Kariuki & Jones, 1995[@bb8]). The blue parallelepipeds are (I)[](#scheme1){ref-type="chem"} and the blue needles are (II)[](#scheme1){ref-type="chem"}.

A 2.012 g (8.37 mmol) sample of potassium 4-sulfo­benzoic acid (Aldrich, 98%) was dissolved in 50 ml of water with gentle heat and stirring. To this colorless solution was added a colorless solution of 1.420 g (8.36 mmol) of AgNO~3~ (Baker) in 25 ml of water. The resulting slightly turbid opalescent mixture was transferred to a porcelain evaporating dish that was set out to evaporate in a fume hood. During the transfer, some white snowy particles were noted in the liquid. After several days, the water had completely evaporated leaving behind colorless crystals of two distinct morphologies, needles and hexa­gonal plates. The needles were identified as (III)[](#scheme1){ref-type="chem"} and the plates as (IV)[](#scheme1){ref-type="chem"} through the single crystal X-ray studies.

Refinement   {#sec5}
============

Crystal data, data collection and structure refinement details are summarized in Table 5[▸](#table5){ref-type="table"}. For (I)[](#scheme1){ref-type="chem"}, hydrogen atoms bonded to carbon atoms and the carb­oxy­lic hydrogen atom were calculated on idealized positions and included in the refinement as riding atoms with C---H = 0.95 Å or O---H = 0.78 Å and their *U* ~iso~ constrained to be 1.2 (C---H) or 1.5 (O---H) times the *U* ~eq~ of the bonding atom. Hydrogen atoms bonded to water oxygen atoms were located in difference-Fourier maps and refined, followed by restraining the O---H distance to be 0.84 Å (DFIX) and constraining their *U* ~iso~ to be 1.5 times the *U* ~eq~ of the bonding atom. All crystals of (II)[](#scheme1){ref-type="chem"} under investigation exhibited twinning and the structure was refined as a two-component twin with a 0.523 (2):0.477 (2) ratio. The twinning law was determined to be a 180° rotation around the triclinic *b* axis. Additionally, the arene rings are statistically disordered over two orientations such that atoms C2, C3, C5, and C6 are split between two positions (designated *A* and *B*) each assigned 50% occupancy. These atoms were refined with isotropic displacement parameters. All other non-hydrogen atoms were refined with anisotropic displacement parameters and full occupancies. The C---H hydrogen atoms were included as riding atoms with fixed distances of 0.93 Å. The O---H hydrogen atoms were located using difference-Fourier syntheses and were refined with their displacement parameters constrained to those of the bonding atoms (distances in Table 2[▸](#table2){ref-type="table"}). In (III)[](#scheme1){ref-type="chem"}, one of the two cation sites showed split positions separated by *ca* 0.2 Å. These were modeled as one containing Ag fixed at 38% occupancy and the other containing K fixed at 62% occupancy. With the other cation site modeled as 100% Ag, the overall composition of the data crystal based on the refinement is Ag~0.69~K~0.31~(O~3~SC~6~H~4~CO~2~H). Energy dispersive X-ray analysis (EDX) of three locations on the data crystal yielded an average Ag/K atom ratio matching the refinement composition. Hydrogen atoms bonded to carbon atoms were calculated on idealized positions and included in the refinement as riding atoms (C---H 0.95Å) with their *U* ~iso~ constrained to be 1.2 times the *U* ~eq~ of the bonding atom. The carb­oxy­lic hydrogen atom was placed on an idealized position with consideration given to the maximum of the electron density. It was then refined as a rotating group (around C7---O1) and *U* ~iso~ was fixed to 1.5 times the *U* ~eq~ of the bonding atom O1. In (IV)[](#scheme1){ref-type="chem"}, the unique cation site was modeled with a fixed 80% K/20% Ag occupancy constraining fractional coordinates and atomic displacement parameters to be the same for Ag and K. Energy dispersive X-ray analysis (EDX) of three locations on the data crystal yielded an average K/Ag atom ratio in reasonable agreement with this 4:1 ratio. In addition, the sulfonate group displayed disorder with two sets of O atom positions (designated *A* and *B*) separated by an approximate 12° rotation about the C---S bond. The occupancies were assigned as 80% *A* and 20% *B*, with the *A* atoms being refined anisotropically and the *B* atoms isotropically. All other non-hydrogen atoms were refined anisotropically. Hydrogen atoms bonded to carbon atoms were calculated on idealized positions and included in the refinement as riding atoms (C---H = 0.95Å) with their *U* ~iso~ constrained to be 1.2 times the *U* ~eq~ of the bonding atom. The carboxyl hydrogen atom was placed on an idealized position with consideration given to the maximum of the electron density. It was then refined as a rotating group (around C7---O1) and *U* ~iso~ was fixed to 1.5 times the *U* ~eq~ of the bonding atom O1. Water hydrogen atoms were located in difference-Fourier maps and refined, followed by restraining the O---H distance to be 0.84 Å (DFIX) and constraining their *U* ~iso~ to be 1.5 times the *U* ~eq~ of the bonding atom.

Supplementary Material
======================

Crystal structure: contains datablock(s) I, II, III, IV, global. DOI: [10.1107/S2056989019014610/mw2148sup1.cif](https://doi.org/10.1107/S2056989019014610/mw2148sup1.cif)

Structure factors: contains datablock(s) I. DOI: [10.1107/S2056989019014610/mw2148Isup2.hkl](https://doi.org/10.1107/S2056989019014610/mw2148Isup2.hkl)

Structure factors: contains datablock(s) II. DOI: [10.1107/S2056989019014610/mw2148IIsup3.hkl](https://doi.org/10.1107/S2056989019014610/mw2148IIsup3.hkl)

Structure factors: contains datablock(s) III. DOI: [10.1107/S2056989019014610/mw2148IIIsup4.hkl](https://doi.org/10.1107/S2056989019014610/mw2148IIIsup4.hkl)

Structure factors: contains datablock(s) IV. DOI: [10.1107/S2056989019014610/mw2148IVsup5.hkl](https://doi.org/10.1107/S2056989019014610/mw2148IVsup5.hkl)

CCDC references: [1961811](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961811), [1961810](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961810), [1961809](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961809), [1961808](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961808), [1961811](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961811), [1961810](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961810), [1961809](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961809), [1961808](https://scripts.iucr.org/cgi-bin/cr.cgi?rm=csd&csdid=1961808)

Additional supporting information: [crystallographic information](https://scripts.iucr.org/cgi-bin/sendsupfiles?mw2148&file=mw2148sup0.html&mime=text/html); [3D view](https://scripts.iucr.org/cgi-bin/sendcif?mw2148sup1&Qmime=cif); [checkCIF report](https://scripts.iucr.org/cgi-bin/paper?mw2148&checkcif=yes)

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Crystal data {#d1e147}
=============================================================================

  ------------------------------------------- ---------------------------------------
  \[Cu(C~7~H~5~O~5~S)~2~(H~2~O)~4~\]·2H~2~O   *Z* = 1
  *M~r~* = 573.97                             *F*(000) = 295
  Triclinic, *P*1                             *D*~x~ = 1.841 Mg m^−3^
  *a* = 6.1907 (1) Å                          Mo *K*α radiation, λ = 0.71073 Å
  *b* = 7.2010 (2) Å                          Cell parameters from 9988 reflections
  *c* = 12.4919 (3) Å                         θ = 3.0--32.9°
  α = 90.310 (1)°                             µ = 1.34 mm^−1^
  β = 94.587 (1)°                             *T* = 130 K
  γ = 111.087 (1)°                            Parallelpiped, light blue
  *V* = 517.57 (2) Å^3^                       0.14 × 0.12 × 0.06 mm
  ------------------------------------------- ---------------------------------------

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Data collection {#d1e289}
================================================================================

  ------------------------------------------------------------------- --------------------------------------
  Bruker APEXII CCD diffractometer                                    3460 reflections with *I* \> 2σ(*I*)
  Radiation source: sealed tube                                       *R*~int~ = 0.011
  φ and ω scans                                                       θ~max~ = 33.0°, θ~min~ = 1.6°
  Absorption correction: multi-scan (SADABS; Krause *et al.*, 2015)   *h* = −9→9
  *T*~min~ = 0.685, *T*~max~ = 0.747                                  *k* = −10→10
  13360 measured reflections                                          *l* = −18→18
  3630 independent reflections                                        
  ------------------------------------------------------------------- --------------------------------------

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Refinement {#d1e405}
===========================================================================

  ------------------------------------- ------------------------------------------------------------------------------------------------
  Refinement on *F*^2^                  Primary atom site location: dual
  Least-squares matrix: full            Secondary atom site location: difference Fourier map
  *R*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.020   Hydrogen site location: mixed
  *wR*(*F*^2^) = 0.057                  H atoms treated by a mixture of independent and constrained refinement
  *S* = 1.14                            *w* = 1/\[σ^2^(*F*~o~^2^) + (0.0245*P*)^2^ + 0.273*P*\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  3630 reflections                      (Δ/σ)~max~ = 0.001
  171 parameters                        Δρ~max~ = 0.51 e Å^−3^
  6 restraints                          Δρ~min~ = −0.43 e Å^−3^
  ------------------------------------- ------------------------------------------------------------------------------------------------

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Special details {#d1e561}
================================================================================

  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å^2^) {#d1e580}
===================================================================================================================================================================

  ----- -------------- -------------- ------------- -------------------- --
        *x*            *y*            *z*           *U*~iso~\*/*U*~eq~   
  Cu1   0.500000       0.500000       0.000000      0.00968 (5)          
  S1    0.30355 (4)    0.79731 (3)    0.16948 (2)   0.00914 (5)          
  O5    0.48130 (13)   0.96708 (11)   0.12629 (6)   0.01327 (14)         
  O4    0.27720 (14)   0.60777 (11)   0.11718 (6)   0.01404 (14)         
  O3    0.08255 (13)   0.82667 (12)   0.17228 (6)   0.01368 (14)         
  O2    0.48509 (16)   0.66679 (14)   0.69906 (7)   0.02187 (17)         
  O1    0.85182 (15)   0.79258 (14)   0.65304 (7)   0.01982 (17)         
  H1    0.8822 (8)     0.785 (3)      0.7143 (16)   0.030\*              
  O6    0.29941 (13)   0.22730 (11)   0.02506 (6)   0.01153 (13)         
  H6B   0.363 (3)      0.154 (2)      0.0511 (13)   0.017\*              
  H6A   0.187 (2)      0.212 (2)      0.0583 (12)   0.017\*              
  O7    0.71588 (13)   0.49375 (12)   0.12393 (6)   0.01239 (13)         
  H7A   0.646 (3)      0.452 (2)      0.1780 (10)   0.019\*              
  H7B   0.818 (2)      0.6062 (16)    0.1396 (13)   0.019\*              
  O8    0.95280 (13)   0.20843 (12)   0.14612 (7)   0.01442 (14)         
  H8B   0.930 (3)      0.3126 (18)    0.1349 (14)   0.022\*              
  H8A   0.8216 (19)    0.119 (2)      0.1378 (14)   0.022\*              
  C4    0.40161 (17)   0.78343 (14)   0.30569 (8)   0.01038 (16)         
  C3    0.23888 (18)   0.71925 (17)   0.38126 (8)   0.01460 (18)         
  H3    0.078164       0.685935       0.360157      0.018\*              
  C2    0.31334 (18)   0.70431 (17)   0.48778 (8)   0.01512 (18)         
  H2    0.203579       0.661662       0.539888      0.018\*              
  C1    0.54914 (18)   0.75198 (15)   0.51796 (8)   0.01165 (16)         
  C6    0.71054 (18)   0.81524 (16)   0.44154 (8)   0.01307 (17)         
  H6    0.871163       0.847484       0.462431      0.016\*              
  C5    0.63753 (17)   0.83133 (16)   0.33499 (8)   0.01266 (17)         
  H5    0.747219       0.874444       0.282876      0.015\*              
  C7    0.62381 (19)   0.73240 (15)   0.63257 (8)   0.01397 (18)         
  ----- -------------- -------------- ------------- -------------------- --

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Atomic displacement parameters (Å^2^) {#d1e954}
======================================================================================================

  ----- -------------- -------------- -------------- ------------- -------------- -------------
        *U*^11^        *U*^22^        *U*^33^        *U*^12^       *U*^13^        *U*^23^
  Cu1   0.00874 (8)    0.01025 (8)    0.00916 (8)    0.00255 (6)   −0.00025 (5)   0.00210 (5)
  S1    0.00890 (10)   0.00930 (10)   0.00886 (10)   0.00283 (8)   0.00080 (7)    0.00029 (7)
  O5    0.0117 (3)     0.0130 (3)     0.0134 (3)     0.0022 (3)    0.0014 (2)     0.0042 (3)
  O4    0.0167 (3)     0.0119 (3)     0.0134 (3)     0.0047 (3)    0.0024 (3)     −0.0024 (3)
  O3    0.0105 (3)     0.0158 (3)     0.0156 (3)     0.0061 (3)    −0.0001 (3)    −0.0002 (3)
  O2    0.0238 (4)     0.0293 (5)     0.0126 (4)     0.0088 (4)    0.0055 (3)     0.0080 (3)
  O1    0.0178 (4)     0.0267 (4)     0.0113 (3)     0.0043 (3)    −0.0021 (3)    0.0023 (3)
  O6    0.0097 (3)     0.0108 (3)     0.0145 (3)     0.0038 (2)    0.0026 (2)     0.0036 (2)
  O7    0.0108 (3)     0.0146 (3)     0.0100 (3)     0.0025 (3)    0.0006 (2)     0.0024 (2)
  O8    0.0109 (3)     0.0127 (3)     0.0188 (4)     0.0033 (3)    0.0013 (3)     0.0041 (3)
  C4    0.0110 (4)     0.0106 (4)     0.0096 (4)     0.0038 (3)    0.0014 (3)     0.0006 (3)
  C3    0.0112 (4)     0.0203 (5)     0.0127 (4)     0.0059 (4)    0.0030 (3)     0.0029 (4)
  C2    0.0137 (4)     0.0196 (5)     0.0119 (4)     0.0052 (4)    0.0044 (3)     0.0039 (4)
  C1    0.0143 (4)     0.0112 (4)     0.0094 (4)     0.0045 (3)    0.0016 (3)     0.0010 (3)
  C6    0.0112 (4)     0.0158 (4)     0.0114 (4)     0.0039 (3)    0.0009 (3)     0.0004 (3)
  C5    0.0107 (4)     0.0158 (4)     0.0106 (4)     0.0033 (3)    0.0023 (3)     0.0007 (3)
  C7    0.0189 (5)     0.0123 (4)     0.0109 (4)     0.0059 (4)    0.0011 (3)     0.0011 (3)
  ----- -------------- -------------- -------------- ------------- -------------- -------------

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Geometric parameters (Å, º) {#d1e1266}
============================================================================================

  --------------------- ------------- ---------------- -------------
  Cu1---O6              1.9520 (7)    O7---H7A         0.831 (9)
  Cu1---O6^i^           1.9521 (7)    O7---H7B         0.840 (9)
  Cu1---O7              1.9743 (7)    O8---H8B         0.822 (9)
  Cu1---O7^i^           1.9743 (7)    O8---H8A         0.832 (9)
  Cu1---O4              2.3934 (8)    C4---C5          1.3916 (14)
  Cu1---O4^i^           2.3934 (8)    C4---C3          1.3934 (14)
  S1---O4               1.4593 (8)    C3---C2          1.3906 (15)
  S1---O5               1.4596 (8)    C3---H3          0.9500
  S1---O3               1.4607 (8)    C2---C1          1.3931 (15)
  S1---C4               1.7760 (10)   C2---H2          0.9500
  O2---C7               1.2152 (13)   C1---C6          1.3954 (14)
  O1---C7               1.3216 (14)   C1---C7          1.4922 (14)
  O1---H1               0.78 (2)      C6---C5          1.3901 (14)
  O6---H6B              0.814 (9)     C6---H6          0.9500
  O6---H6A              0.813 (9)     C5---H5          0.9500
                                                       
  O6---Cu1---O6^i^      180.00 (3)    Cu1---O7---H7A   111.5 (12)
  O6---Cu1---O7         90.38 (3)     Cu1---O7---H7B   112.3 (12)
  O6^i^---Cu1---O7      89.62 (3)     H7A---O7---H7B   108.6 (16)
  O6---Cu1---O7^i^      89.62 (3)     H8B---O8---H8A   104.9 (17)
  O6^i^---Cu1---O7^i^   90.38 (3)     C5---C4---C3     121.01 (9)
  O7---Cu1---O7^i^      180.0         C5---C4---S1     119.92 (7)
  O6---Cu1---O4         87.38 (3)     C3---C4---S1     119.05 (8)
  O6^i^---Cu1---O4      92.62 (3)     C2---C3---C4     119.54 (9)
  O7---Cu1---O4         90.00 (3)     C2---C3---H3     120.2
  O7^i^---Cu1---O4      90.01 (3)     C4---C3---H3     120.2
  O6---Cu1---O4^i^      92.62 (3)     C3---C2---C1     119.90 (9)
  O6^i^---Cu1---O4^i^   87.38 (3)     C3---C2---H2     120.0
  O7---Cu1---O4^i^      90.01 (3)     C1---C2---H2     120.0
  O7^i^---Cu1---O4^i^   89.99 (3)     C2---C1---C6     120.09 (9)
  O4---Cu1---O4^i^      180.0         C2---C1---C7     118.74 (9)
  O4---S1---O5          113.02 (5)    C6---C1---C7     121.17 (9)
  O4---S1---O3          112.56 (5)    C5---C6---C1     120.35 (9)
  O5---S1---O3          112.31 (5)    C5---C6---H6     119.8
  O4---S1---C4          106.04 (5)    C1---C6---H6     119.8
  O5---S1---C4          106.46 (5)    C6---C5---C4     119.11 (9)
  O3---S1---C4          105.77 (5)    C6---C5---H5     120.4
  S1---O4---Cu1         134.82 (5)    C4---C5---H5     120.4
  C7---O1---H1          109.5         O2---C7---O1     124.44 (10)
  Cu1---O6---H6B        116.7 (12)    O2---C7---C1     122.18 (10)
  Cu1---O6---H6A        117.3 (12)    O1---C7---C1     113.39 (9)
  H6B---O6---H6A        106.8 (16)                     
  --------------------- ------------- ---------------- -------------

Symmetry code: (i) −*x*+1, −*y*+1, −*z*.

Tetraaquabis(4-carboxybenzenesulfonato)copper(II) dihydrate (I). Hydrogen-bond geometry (Å, º) {#d1e1719}
==============================================================================================

  ---------------------- ---------- ---------- ------------- ---------------
  *D*---H···*A*          *D*---H    H···*A*    *D*···*A*     *D*---H···*A*
  O1---H1···O8^ii^       0.78       1.94       2.6979 (12)   164
  O6---H6*B*···O5^iii^   0.81 (1)   1.97 (1)   2.7738 (11)   172 (2)
  O6---H6*A*···O8^iv^    0.81 (1)   1.88 (1)   2.6872 (11)   172 (2)
  O7---H7*A*···O2^v^     0.83 (1)   1.86 (1)   2.6845 (11)   171 (2)
  O7---H7*B*···O3^vi^    0.84 (1)   1.84 (1)   2.6672 (11)   169 (2)
  O8---H8*B*···O7        0.82 (1)   2.17 (1)   2.9255 (11)   153 (2)
  O8---H8*A*···O5^iii^   0.83 (1)   1.99 (1)   2.7984 (11)   165 (2)
  ---------------------- ---------- ---------- ------------- ---------------

Symmetry codes: (ii) −*x*+2, −*y*+1, −*z*+1; (iii) *x*, *y*−1, *z*; (iv) *x*−1, *y*, *z*; (v) −*x*+1, −*y*+1, −*z*+1; (vi) *x*+1, *y*, *z*.

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Crystal data {#d1e1951}
===============================================================

  ------------------------------------ ---------------------------------------
  \[Cu(H~2~O)~6~\](C~7~H~5~O~5~S)~2~   *Z* = 1
  *M~r~* = 573.97                      *F*(000) = 295
  Triclinic, *P*1                      *D*~x~ = 1.822 Mg m^−3^
  *a* = 6.4380 (13) Å                  Mo *K*α radiation, λ = 0.71073 Å
  *b* = 7.2431 (14) Å                  Cell parameters from 4072 reflections
  *c* = 12.088 (2) Å                   θ = 3.3--33.0°
  α = 72.60 (3)°                       µ = 1.33 mm^−1^
  β = 77.20 (3)°                       *T* = 130 K
  γ = 82.13 (3)°                       Thin plate, light blue
  *V* = 523.0 (2) Å^3^                 0.21 × 0.08 × 0.02 mm
  ------------------------------------ ---------------------------------------

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Data collection {#d1e2089}
==================================================================

  ---------------------------------------------------------------- --------------------------------------
  Bruker APEXII CCD diffractometer                                 3370 reflections with *I* \> 2σ(*I*)
  Radiation source: sealed tube                                    *R*~int~ = 0.045
  φ and ω scans                                                    θ~max~ = 33.0°, θ~min~ = 3.0°
  Absorption correction: multi-scan (*TWINABS*; Sheldrick, 1996)   *h* = −9→9
  *T*~min~ = 0.585, *T*~max~ = 0.747                               *k* = −10→10
  3738 measured reflections                                        *l* = 0→18
  3738 independent reflections                                     
  ---------------------------------------------------------------- --------------------------------------

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Refinement {#d1e2202}
=============================================================

  ------------------------------------- ------------------------------------------------------------------------------------------------
  Refinement on *F*^2^                  Primary atom site location: structure-invariant direct methods
  Least-squares matrix: full            Secondary atom site location: difference Fourier map
  *R*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.059   Hydrogen site location: mixed
  *wR*(*F*^2^) = 0.139                  H atoms treated by a mixture of independent and constrained refinement
  *S* = 1.18                            *w* = 1/\[σ^2^(*F*~o~^2^) + (0.0332*P*)^2^ + 2.049*P*\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  3738 reflections                      (Δ/σ)~max~ = 0.001
  169 parameters                        Δρ~max~ = 0.84 e Å^−3^
  18 restraints                         Δρ~min~ = −1.19 e Å^−3^
  ------------------------------------- ------------------------------------------------------------------------------------------------

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Special details {#d1e2358}
==================================================================

  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
  Refinement. Refined as a 2-component twin. BASF refines to: 0.47690
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å^2^) {#d1e2383}
=====================================================================================================================================================

  ----- -------------- -------------- -------------- -------------------- ------------
        *x*            *y*            *z*            *U*~iso~\*/*U*~eq~   Occ. (\<1)
  Cu1   0.5000         1.0000         0.0000         0.00922 (14)         
  S1    0.89992 (13)   0.53760 (18)   0.82865 (7)    0.01095 (17)         
  O5    1.0191 (5)     0.3517 (5)     0.8217 (3)     0.0173 (6)           
  O4    0.7159 (4)     0.5122 (5)     0.92630 (19)   0.0115 (4)           
  O3    1.0340 (5)     0.6825 (4)     0.8291 (3)     0.0162 (7)           
  O2    0.6930 (5)     0.9432 (6)     0.2844 (3)     0.0241 (7)           
  O1    0.3772 (5)     0.8181 (7)     0.3778 (3)     0.0256 (7)           
  H1    0.333 (10)     0.874 (12)     0.313 (6)      0.038\*              
  O6    0.6358 (5)     0.7475 (5)     0.0720 (3)     0.0135 (6)           
  H61   0.744 (6)      0.733 (8)      0.102 (4)      0.020\*              
  H62   0.639 (8)      0.656 (6)      0.042 (5)      0.020\*              
  O7    0.6741 (5)     1.1291 (5)     0.0619 (3)     0.0145 (6)           
  H71   0.700 (9)      1.245 (4)      0.035 (4)      0.022\*              
  H72   0.706 (9)      1.082 (7)      0.128 (3)      0.022\*              
  O8    0.2112 (4)     0.9557 (5)     0.1819 (2)     0.0128 (5)           
  H81   0.124 (7)      1.056 (5)      0.175 (5)      0.019\*              
  H82   0.143 (8)      0.863 (6)      0.186 (5)      0.019\*              
  C4    0.7954 (6)     0.6287 (8)     0.6968 (3)     0.0168 (8)           
  C3A   0.6064 (13)    0.5844 (14)    0.6900 (7)     0.0106 (13)\*        0.5
  H3A   0.5218         0.5095         0.7567         0.013\*              0.5
  C2A   0.5338 (14)    0.6495 (14)    0.5834 (7)     0.0134 (15)\*        0.5
  H2A   0.4059         0.6102         0.5777         0.016\*              0.5
  C3B   0.5727 (13)    0.6505 (16)    0.7017 (7)     0.0158 (14)\*        0.5
  H3B   0.4774         0.6196         0.7735         0.019\*              0.5
  C2B   0.5006 (14)    0.7198 (15)    0.5951 (7)     0.0173 (16)\*        0.5
  H2B   0.3551         0.7325         0.5947         0.021\*              0.5
  C1    0.6503 (6)     0.7712 (6)     0.4869 (3)     0.0155 (8)           
  C6A   0.8529 (12)    0.8324 (15)    0.4945 (6)     0.0144 (13)\*        0.5
  H6A   0.9325         0.9140         0.4288         0.017\*              0.5
  C5A   0.9247 (12)    0.7684 (15)    0.5998 (6)     0.0156 (13)\*        0.5
  H5A   1.0479         0.8108         0.6093         0.019\*              0.5
  C6B   0.8561 (12)    0.7127 (16)    0.4865 (7)     0.0174 (13)\*        0.5
  H6B   0.9507         0.7289         0.4146         0.021\*              0.5
  C5B   0.9332 (13)    0.6284 (14)    0.5903 (7)     0.0183 (15)\*        0.5
  H5B   1.0727         0.5734         0.5887         0.022\*              0.5
  C7    0.5754 (7)     0.8560 (6)     0.3725 (4)     0.0155 (8)           
  ----- -------------- -------------- -------------- -------------------- ------------

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Atomic displacement parameters (Å^2^) {#d1e2871}
========================================================================================

  ----- ------------- ------------- ------------- -------------- --------------- --------------
        *U*^11^       *U*^22^       *U*^33^       *U*^12^        *U*^13^         *U*^23^
  Cu1   0.0126 (3)    0.0084 (3)    0.0077 (2)    −0.0002 (3)    −0.00533 (19)   −0.0016 (3)
  S1    0.0104 (4)    0.0135 (4)    0.0097 (3)    0.0005 (4)     −0.0037 (3)     −0.0037 (4)
  O5    0.0155 (14)   0.0217 (17)   0.0183 (14)   0.0048 (12)    −0.0086 (11)    −0.0099 (12)
  O4    0.0124 (11)   0.0130 (13)   0.0080 (9)    −0.0008 (13)   −0.0021 (8)     −0.0013 (12)
  O3    0.0147 (14)   0.0132 (17)   0.0231 (15)   −0.0041 (11)   −0.0030 (11)    −0.0078 (11)
  O2    0.0245 (15)   0.0318 (19)   0.0118 (12)   −0.0011 (15)   −0.0060 (11)    0.0017 (14)
  O1    0.0266 (15)   0.037 (2)     0.0147 (12)   −0.0015 (18)   −0.0124 (11)    −0.0029 (17)
  O6    0.0178 (14)   0.0099 (14)   0.0148 (13)   0.0014 (11)    −0.0073 (11)    −0.0045 (11)
  O7    0.0203 (15)   0.0140 (15)   0.0115 (12)   −0.0077 (11)   −0.0087 (11)    −0.0001 (11)
  O8    0.0123 (11)   0.0131 (14)   0.0144 (10)   −0.0003 (12)   −0.0044 (9)     −0.0048 (12)
  C4    0.0129 (15)   0.029 (2)     0.0088 (13)   0.0015 (18)    −0.0038 (11)    −0.0056 (18)
  C1    0.0185 (18)   0.019 (2)     0.0090 (14)   0.0053 (14)    −0.0045 (12)    −0.0051 (13)
  C7    0.026 (2)     0.0118 (17)   0.0115 (15)   0.0016 (14)    −0.0075 (14)    −0.0058 (13)
  ----- ------------- ------------- ------------- -------------- --------------- --------------

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Geometric parameters (Å, º) {#d1e3177}
==============================================================================

  --------------------- ------------- ----------------- ------------
  Cu1---O7              1.941 (3)     C4---C5B          1.393 (9)
  Cu1---O7^i^           1.941 (3)     C4---C3B          1.411 (9)
  Cu1---O6^i^           1.953 (3)     C4---C5A          1.476 (9)
  Cu1---O6              1.953 (3)     C3A---C2A         1.395 (11)
  Cu1---O8              2.515 (3)     C3A---H3A         0.9300
  Cu1---O8^i^           2.515 (3)     C2A---C1          1.370 (9)
  S1---O3               1.449 (3)     C2A---H2A         0.9300
  S1---O4               1.463 (2)     C3B---C2B         1.394 (11)
  S1---O5               1.472 (4)     C3B---H3B         0.9300
  S1---C4               1.776 (4)     C2B---C1          1.424 (9)
  O2---C7               1.216 (5)     C2B---H2B         0.9300
  O1---C7               1.325 (6)     C1---C6B          1.334 (9)
  O1---H1               0.86 (7)      C1---C6A          1.464 (9)
  O6---H61              0.84 (2)      C1---C7           1.493 (5)
  O6---H62              0.84 (2)      C6A---C5A         1.377 (10)
  O7---H71              0.83 (2)      C6A---H6A         0.9300
  O7---H72              0.83 (2)      C5A---H5A         0.9300
  O8---H81              0.85 (2)      C6B---C5B         1.388 (11)
  O8---H82              0.84 (2)      C6B---H6B         0.9300
  C4---C3A              1.326 (9)     C5B---H5B         0.9300
                                                        
  O7---Cu1---O7^i^      180.0         C4---C3A---H3A    119.8
  O7---Cu1---O6^i^      89.23 (12)    C2A---C3A---H3A   119.8
  O7^i^---Cu1---O6^i^   90.77 (12)    C1---C2A---C3A    120.3 (7)
  O7---Cu1---O6         90.77 (12)    C1---C2A---H2A    119.9
  O7^i^---Cu1---O6      89.23 (12)    C3A---C2A---H2A   119.9
  O6^i^---Cu1---O6      180.0         C2B---C3B---C4    117.6 (7)
  O7---Cu1---O8         92.88 (12)    C2B---C3B---H3B   121.2
  O7^i^---Cu1---O8      87.12 (12)    C4---C3B---H3B    121.2
  O8---Cu1---O8^i^      180.0         C3B---C2B---C1    119.8 (7)
  O6---Cu1---O8         89.03 (12)    C3B---C2B---H2B   120.1
  O6---Cu1---O8^i^      90.97 (12)    C1---C2B---H2B    120.1
  O3---S1---O4          112.4 (2)     C6B---C1---C2B    118.9 (6)
  O3---S1---O5          113.31 (17)   C2A---C1---C6A    120.3 (5)
  O4---S1---O5          112.1 (2)     C6B---C1---C7     119.6 (5)
  O3---S1---C4          106.3 (2)     C2A---C1---C7     123.0 (5)
  O4---S1---C4          106.37 (16)   C2B---C1---C7     120.5 (5)
  O5---S1---C4          105.8 (2)     C6A---C1---C7     116.6 (4)
  C7---O1---H1          112 (4)       C5A---C6A---C1    119.5 (7)
  Cu1---O6---H61        124 (4)       C5A---C6A---H6A   120.2
  Cu1---O6---H62        119 (4)       C1---C6A---H6A    120.2
  H61---O6---H62        108 (4)       C6A---C5A---C4    116.4 (7)
  Cu1---O7---H71        125 (4)       C6A---C5A---H5A   121.8
  Cu1---O7---H72        123 (3)       C4---C5A---H5A    121.8
  H71---O7---H72        111 (4)       C1---C6B---C5B    122.0 (7)
  H81---O8---H82        107 (3)       C1---C6B---H6B    119.0
  C5B---C4---C3B        119.5 (5)     C5B---C6B---H6B   119.0
  C3A---C4---C5A        122.7 (5)     C6B---C5B---C4    118.0 (7)
  C3A---C4---S1         121.7 (4)     C6B---C5B---H5B   121.0
  C5B---C4---S1         118.0 (4)     C4---C5B---H5B    121.0
  C3B---C4---S1         120.3 (4)     O2---C7---O1      125.5 (4)
  C5A---C4---S1         115.4 (4)     O2---C7---C1      121.3 (4)
  C4---C3A---C2A        120.3 (7)     O1---C7---C1      113.1 (4)
  --------------------- ------------- ----------------- ------------

Symmetry code: (i) −*x*+1, −*y*+2, −*z*.

Hexaaquacopper(II) 4-carboxybenzenesulfonate (II). Hydrogen-bond geometry (Å, º) {#d1e3718}
================================================================================

  -------------------- ---------- ---------- ----------- ---------------
  *D*---H···*A*        *D*---H    H···*A*    *D*···*A*   *D*---H···*A*
  O1---H1···O8         0.86 (7)   1.83 (7)   2.677 (4)   170 (7)
  O6---H61···O5^ii^    0.84 (2)   1.89 (3)   2.717 (4)   169 (5)
  O6---H62···O4^iii^   0.84 (2)   1.93 (3)   2.725 (5)   158 (5)
  O7---H71···O4^iv^    0.83 (2)   1.99 (3)   2.784 (5)   160 (5)
  O7---H72···O2        0.83 (2)   1.84 (3)   2.645 (4)   161 (5)
  O8---H81···O3^v^     0.85 (2)   2.02 (3)   2.851 (5)   167 (5)
  O8---H82···O5^vi^    0.84 (2)   2.02 (3)   2.854 (5)   175 (5)
  -------------------- ---------- ---------- ----------- ---------------

Symmetry codes: (ii) −*x*+2, −*y*+1, −*z*+1; (iii) *x*, *y*, *z*−1; (iv) *x*, *y*+1, *z*−1; (v) −*x*+1, −*y*+2, −*z*+1; (vi) −*x*+1, −*y*+1, −*z*+1.

Silver potassium 4-carboxybenzenesulfonate (III). Crystal data {#d1e3936}
==============================================================

  ------------------------------------ ---------------------------------------
  \[Ag~0.69~K~0.31~\](C~7~H~5~O~5~S)   *F*(000) = 1130.6
  *M~r~* = 287.72                      *D*~x~ = 2.368 Mg m^−3^
  Monoclinic, *C*2/*c*                 Mo *K*α radiation, λ = 0.71073 Å
  *a* = 19.436 (3) Å                   Cell parameters from 7014 reflections
  *b* = 15.644 (3) Å                   θ = 2.6--30.4°
  *c* = 5.3355 (9) Å                   µ = 2.17 mm^−1^
  β = 95.651 (2)°                      *T* = 120 K
  *V* = 1614.4 (5) Å^3^                Needle, colorless
  *Z* = 8                              0.16 × 0.06 × 0.03 mm
  ------------------------------------ ---------------------------------------

Silver potassium 4-carboxybenzenesulfonate (III). Data collection {#d1e4063}
=================================================================

  ------------------------------------------------------------------- --------------------------------------
  Bruker APEXII CCD diffractometer                                    2435 independent reflections
  Radiation source: fine-focus sealed tube                            2223 reflections with *I* \> 2σ(*I*)
  Curved graphite crystal monochromator                               *R*~int~ = 0.020
  ω scans                                                             θ~max~ = 30.4°, θ~min~ = 1.7°
  Absorption correction: multi-scan (SADABS; Krause *et al.*, 2015)   *h* = −27→27
  *T*~min~ = 0.572, *T*~max~ = 0.648                                  *k* = −22→22
  12751 measured reflections                                          *l* = −7→7
  ------------------------------------------------------------------- --------------------------------------

Silver potassium 4-carboxybenzenesulfonate (III). Refinement {#d1e4177}
============================================================

  ------------------------------------- ------------------------------------------------------------------------------------------------
  Refinement on *F*^2^                  Primary atom site location: dual
  Least-squares matrix: full            Secondary atom site location: difference Fourier map
  *R*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.017   Hydrogen site location: inferred from neighbouring sites
  *wR*(*F*^2^) = 0.043                  H atoms treated by a mixture of independent and constrained refinement
  *S* = 1.08                            *w* = 1/\[σ^2^(*F*~o~^2^) + (0.021*P*)^2^ + 1.6847*P*\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  2435 reflections                      (Δ/σ)~max~ = 0.001
  135 parameters                        Δρ~max~ = 0.51 e Å^−3^
  0 restraints                          Δρ~min~ = −0.36 e Å^−3^
  ------------------------------------- ------------------------------------------------------------------------------------------------

Silver potassium 4-carboxybenzenesulfonate (III). Special details {#d1e4333}
=================================================================

  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Silver potassium 4-carboxybenzenesulfonate (III). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å^2^) {#d1e4352}
====================================================================================================================================================

  ----- ------------- -------------- ------------- -------------------- ------------
        *x*           *y*            *z*           *U*~iso~\*/*U*~eq~   Occ. (\<1)
  Ag1   0.500000      0.54234 (2)    0.750000      0.01208 (5)          
  Ag2   0.500000      0.2558 (3)     0.250000      0.0138 (5)           0.38
  K2    0.500000      0.2420 (5)     0.250000      0.0119 (6)           0.62
  S1    0.39857 (2)   0.35832 (2)    0.72451 (6)   0.00889 (7)          
  O1    0.08310 (6)   0.41836 (8)    0.1298 (2)    0.0193 (2)           
  H1    0.0452 (12)   0.4128 (14)    0.0891 (18)   0.029\*              
  O2    0.05037 (5)   0.38234 (8)    0.5066 (2)    0.0210 (2)           
  O3    0.43544 (5)   0.35558 (7)    0.4987 (2)    0.0145 (2)           
  O4    0.41399 (5)   0.43608 (7)    0.8736 (2)    0.0130 (2)           
  O5    0.40550 (5)   0.28066 (7)    0.8741 (2)    0.0155 (2)           
  C1    0.17074 (7)   0.38502 (9)    0.4510 (3)    0.0130 (3)           
  C2    0.22060 (7)   0.41777 (9)    0.3068 (3)    0.0140 (3)           
  H2    0.206693      0.445860       0.152193      0.017\*              
  C3    0.29056 (7)   0.40970 (9)    0.3872 (3)    0.0127 (3)           
  H3    0.324600      0.432562       0.289897      0.015\*              
  C4    0.30975 (7)   0.36746 (9)    0.6130 (3)    0.0100 (2)           
  C5    0.26050 (7)   0.33392 (10)   0.7577 (3)    0.0136 (3)           
  H5    0.274541      0.304689       0.910281      0.016\*              
  C6    0.19057 (7)   0.34337 (10)   0.6781 (3)    0.0154 (3)           
  H6    0.156577      0.321642       0.777569      0.018\*              
  C7    0.09604 (7)   0.39454 (10)   0.3672 (3)    0.0159 (3)           
  ----- ------------- -------------- ------------- -------------------- ------------

Silver potassium 4-carboxybenzenesulfonate (III). Atomic displacement parameters (Å^2^) {#d1e4644}
=======================================================================================

  ----- -------------- -------------- -------------- --------------- -------------- ---------------
        *U*^11^        *U*^22^        *U*^33^        *U*^12^         *U*^13^        *U*^23^
  Ag1   0.01209 (7)    0.01398 (8)    0.01001 (7)    0.000           0.00026 (5)    0.000
  Ag2   0.0148 (4)     0.0146 (12)    0.0123 (4)     0.000           0.0023 (3)     0.000
  K2    0.0102 (6)     0.014 (2)      0.0113 (6)     0.000           0.0009 (4)     0.000
  S1    0.00656 (13)   0.01002 (15)   0.01008 (15)   −0.00029 (10)   0.00077 (11)   −0.00019 (11)
  O1    0.0113 (5)     0.0227 (6)     0.0223 (6)     −0.0008 (4)     −0.0068 (4)    0.0043 (4)
  O2    0.0095 (5)     0.0330 (6)     0.0199 (5)     0.0031 (4)      −0.0021 (4)    −0.0051 (5)
  O3    0.0110 (5)     0.0195 (5)     0.0140 (5)     0.0004 (4)      0.0053 (4)     −0.0017 (4)
  O4    0.0104 (4)     0.0130 (5)     0.0150 (5)     −0.0009 (4)     −0.0016 (4)    −0.0036 (4)
  O5    0.0119 (5)     0.0137 (5)     0.0204 (5)     0.0003 (4)      −0.0006 (4)    0.0056 (4)
  C1    0.0093 (6)     0.0142 (6)     0.0148 (6)     0.0005 (5)      −0.0029 (5)    −0.0039 (5)
  C2    0.0132 (6)     0.0141 (6)     0.0139 (6)     −0.0001 (5)     −0.0028 (5)    0.0011 (5)
  C3    0.0118 (6)     0.0136 (6)     0.0125 (6)     −0.0018 (5)     0.0004 (5)     0.0011 (5)
  C4    0.0077 (5)     0.0107 (6)     0.0113 (6)     −0.0002 (4)     −0.0003 (5)    −0.0019 (5)
  C5    0.0091 (6)     0.0192 (7)     0.0125 (6)     −0.0004 (5)     0.0005 (5)     0.0025 (5)
  C6    0.0088 (6)     0.0228 (7)     0.0146 (6)     −0.0018 (5)     0.0009 (5)     0.0004 (5)
  C7    0.0115 (6)     0.0151 (7)     0.0200 (7)     0.0015 (5)      −0.0047 (5)    −0.0036 (5)
  ----- -------------- -------------- -------------- --------------- -------------- ---------------

Silver potassium 4-carboxybenzenesulfonate (III). Geometric parameters (Å, º) {#d1e4977}
=============================================================================

  ------------------------- ------------- --------------------- -------------
  Ag1---O4                  2.4919 (11)   S1---O5               1.4525 (11)
  Ag1---O4^i^               2.4920 (11)   S1---O3               1.4616 (11)
  Ag1---O3^ii^              2.4928 (11)   S1---O4               1.4682 (11)
  Ag1---O3^iii^             2.4928 (11)   S1---C4               1.7756 (14)
  Ag1---O4^iv^              2.5061 (10)   O1---C7               1.3205 (19)
  Ag1---O4^v^               2.5061 (10)   O1---H1               0.75 (2)
  Ag1---Ag1^iii^            2.9785 (4)    O2---C7               1.2282 (19)
  Ag1---Ag1^iv^             2.9785 (4)    C1---C2               1.393 (2)
  Ag1---Ag2^iii^            3.158 (5)     C1---C6               1.396 (2)
  Ag1---K2^iii^             3.373 (8)     C1---C7               1.4840 (19)
  Ag2---O3^vi^              2.470 (3)     C2---C3               1.3906 (19)
  Ag2---O3                  2.470 (3)     C2---H2               0.9500
  K2---O2^vii^              2.584 (6)     C3---C4               1.3925 (19)
  K2---O2^viii^             2.584 (6)     C3---H3               0.9500
  K2---O3^vi^               2.611 (6)     C4---C5               1.3904 (19)
  K2---O3                   2.612 (6)     C5---C6               1.3913 (19)
  K2---O5^i^                2.653 (2)     C5---H5               0.9500
  K2---O5^ix^               2.653 (2)     C6---H6               0.9500
                                                                
  O4---Ag1---O4^i^          96.32 (5)     O3---S1---C4          105.40 (7)
  O4---Ag1---O3^ii^         84.29 (4)     O4---S1---C4          104.75 (6)
  O4^i^---Ag1---O3^ii^      162.59 (4)    C7---O1---H1          109.5
  O4---Ag1---O3^iii^        162.59 (4)    C7---O2---K2^viii^    138.90 (15)
  O4^i^---Ag1---O3^iii^     84.29 (4)     S1---O3---Ag2         141.04 (10)
  O3^ii^---Ag1---O3^iii^    100.33 (5)    S1---O3---Ag1^iii^    137.17 (6)
  O4---Ag1---O4^iv^         106.84 (3)    Ag2---O3---Ag1^iii^   79.04 (9)
  O4^i^---Ag1---O4^iv^      83.68 (4)     S1---O3---K2          137.55 (14)
  O3^ii^---Ag1---O4^iv^     79.52 (4)     Ag1^iii^---O3---K2    82.70 (13)
  O3^iii^---Ag1---O4^iv^    90.53 (4)     S1---O4---Ag1         121.05 (6)
  O4---Ag1---O4^v^          83.68 (4)     S1---O4---Ag1^iv^     129.07 (6)
  O4^i^---Ag1---O4^v^       106.84 (3)    Ag1---O4---Ag1^iv^    73.16 (3)
  O3^ii^---Ag1---O4^v^      90.53 (4)     S1---O5---K2^x^       128.74 (17)
  O3^iii^---Ag1---O4^v^     79.52 (4)     C2---C1---C6          120.23 (13)
  O4^iv^---Ag1---O4^v^      164.51 (5)    C2---C1---C7          120.64 (13)
  O3^vi^---Ag2---O3         101.60 (17)   C6---C1---C7          119.14 (13)
  O2^vii^---K2---O2^viii^   82.3 (2)      C3---C2---C1          120.56 (13)
  O2^vii^---K2---O3^vi^     91.83 (4)     C3---C2---H2          119.7
  O2^viii^---K2---O3^vi^    172.8 (2)     C1---C2---H2          119.7
  O2^vii^---K2---O3         172.8 (2)     C2---C3---C4          118.71 (13)
  O2^viii^---K2---O3        91.84 (4)     C2---C3---H3          120.6
  O3^vi^---K2---O3          94.3 (3)      C4---C3---H3          120.6
  O2^vii^---K2---O5^i^      106.44 (13)   C5---C4---C3          121.28 (13)
  O2^viii^---K2---O5^i^     93.44 (10)    C5---C4---S1          118.90 (11)
  O3^vi^---K2---O5^i^       84.13 (15)    C3---C4---S1          119.80 (10)
  O3---K2---O5^i^           78.01 (13)    C4---C5---C6          119.71 (13)
  O2^vii^---K2---O5^ix^     93.44 (10)    C4---C5---H5          120.1
  O2^viii^---K2---O5^ix^    106.44 (13)   C6---C5---H5          120.1
  O3^vi^---K2---O5^ix^      78.01 (13)    C5---C6---C1          119.50 (13)
  O3---K2---O5^ix^          84.13 (15)    C5---C6---H6          120.3
  O5^i^---K2---O5^ix^       153.7 (3)     C1---C6---H6          120.3
  O5---S1---O3              113.70 (6)    O2---C7---O1          122.99 (13)
  O5---S1---O4              113.11 (7)    O2---C7---C1          123.07 (14)
  O3---S1---O4              112.35 (6)    O1---C7---C1          113.94 (13)
  O5---S1---C4              106.62 (6)                          
  ------------------------- ------------- --------------------- -------------

Symmetry codes: (i) −*x*+1, *y*, −*z*+3/2; (ii) *x*, −*y*+1, *z*+1/2; (iii) −*x*+1, −*y*+1, −*z*+1; (iv) −*x*+1, −*y*+1, −*z*+2; (v) *x*, −*y*+1, *z*−1/2; (vi) −*x*+1, *y*, −*z*+1/2; (vii) *x*+1/2, −*y*+1/2, *z*−1/2; (viii) −*x*+1/2, −*y*+1/2, −*z*+1; (ix) *x*, *y*, *z*−1; (x) *x*, *y*, *z*+1.

Silver potassium 4-carboxybenzenesulfonate (III). Hydrogen-bond geometry (Å, º) {#d1e5788}
===============================================================================

  ------------------ --------- --------- ------------- ---------------
  *D*---H···*A*      *D*---H   H···*A*   *D*···*A*     *D*---H···*A*
  O1---H1···O2^xi^   0.75      1.94      2.6841 (16)   172
  ------------------ --------- --------- ------------- ---------------

Symmetry code: (xi) −*x*, *y*, −*z*+1/2.

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Crystal data {#d1e5875}
============================================================================

  ------------------------------------------- ---------------------------------------
  \[Ag~0.20~K~0.80~\](C~7~H~5~O~5~S)·2H~2~O   *F*(000) = 590.4
  *M~r~* = 290.06                             *D*~x~ = 1.813 Mg m^−3^
  Monoclinic, *P*2~1~/*c*                     Mo *K*α radiation, λ = 0.71073 Å
  *a* = 12.8018 (7) Å                         Cell parameters from 8713 reflections
  *b* = 9.9170 (6) Å                          θ = 2.6--30.6°
  *c* = 8.4013 (5) Å                          µ = 0.99 mm^−1^
  β = 94.747 (1)°                             *T* = 120 K
  *V* = 1062.93 (11) Å^3^                     Plate, colorless
  *Z* = 4                                     0.23 × 0.17 × 0.07 mm
  ------------------------------------------- ---------------------------------------

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Data collection {#d1e6009}
===============================================================================

  ------------------------------------------------------------------- --------------------------------------
  Bruker APEXII CCD diffractometer                                    3255 independent reflections
  Radiation source: fine-focus sealed tube                            2831 reflections with *I* \> 2σ(*I*)
  Curved graphite crystal monochromator                               *R*~int~ = 0.023
  ω scans                                                             θ~max~ = 30.6°, θ~min~ = 1.6°
  Absorption correction: multi-scan (SADABS; Krause *et al.*, 2015)   *h* = −18→18
  *T*~min~ = 0.666, *T*~max~ = 0.746                                  *k* = −14→14
  16575 measured reflections                                          *l* = −12→12
  ------------------------------------------------------------------- --------------------------------------

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Refinement {#d1e6123}
==========================================================================

  ------------------------------------- -------------------------------------------------------------------------------------------------
  Refinement on *F*^2^                  Primary atom site location: dual
  Least-squares matrix: full            Secondary atom site location: difference Fourier map
  *R*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.025   Hydrogen site location: mixed
  *wR*(*F*^2^) = 0.063                  H atoms treated by a mixture of independent and constrained refinement
  *S* = 1.08                            *w* = 1/\[σ^2^(*F*~o~^2^) + (0.0273*P*)^2^ + 0.5631*P*\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  3255 reflections                      (Δ/σ)~max~ = 0.003
  171 parameters                        Δρ~max~ = 0.44 e Å^−3^
  4 restraints                          Δρ~min~ = −0.54 e Å^−3^
  ------------------------------------- -------------------------------------------------------------------------------------------------

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Special details {#d1e6279}
===============================================================================

  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.
  -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å^2^) {#d1e6298}
==================================================================================================================================================================

  ----- -------------- -------------- -------------- -------------------- ------------
        *x*            *y*            *z*            *U*~iso~\*/*U*~eq~   Occ. (\<1)
  K1    0.95958 (2)    0.23895 (2)    0.86257 (3)    0.02002 (6)          0.8
  Ag1   0.95958 (2)    0.23895 (2)    0.86257 (3)    0.02002 (6)          0.2
  S1    0.14513 (2)    0.39457 (3)    0.64063 (4)    0.01598 (7)          
  O1    0.66150 (8)    0.46300 (11)   0.81388 (14)   0.0255 (2)           
  H1    0.7195 (16)    0.4598 (16)    0.8542 (19)    0.038\*              
  O2    0.63265 (8)    0.30700 (11)   0.99903 (14)   0.0273 (2)           
  O3A   0.14016 (19)   0.4401 (3)     0.4747 (3)     0.0212 (4)           0.8
  O4A   0.0969 (2)     0.4883 (3)     0.7438 (3)     0.0233 (5)           0.8
  O5A   0.1049 (2)     0.2565 (3)     0.6567 (3)     0.0267 (6)           0.8
  O3B   0.1341 (10)    0.4662 (10)    0.4939 (15)    0.021 (2)\*          0.2
  O4B   0.0914 (9)     0.4677 (11)    0.7709 (13)    0.0120 (18)\*        0.2
  O5B   0.1040 (9)     0.2604 (12)    0.6199 (11)    0.0091 (16)\*        0.2
  O6    0.85970 (8)    0.48285 (10)   0.92292 (13)   0.0215 (2)           
  H6B   0.8713 (15)    0.488 (2)      1.0224 (12)    0.032\*              
  H6A   0.8720 (15)    0.5598 (12)    0.886 (2)      0.032\*              
  O7    0.83434 (9)    0.21551 (11)   1.10503 (15)   0.0291 (2)           
  H7B   0.8305 (17)    0.1320 (10)    1.093 (3)      0.044\*              
  H7A   0.7743 (10)    0.245 (2)      1.077 (3)      0.044\*              
  C1    0.48842 (10)   0.38754 (13)   0.82761 (16)   0.0161 (2)           
  C2    0.45462 (10)   0.47615 (14)   0.70582 (17)   0.0196 (3)           
  H2    0.503151       0.535768       0.662918       0.024\*              
  C3    0.34987 (10)   0.47766 (14)   0.64666 (17)   0.0198 (3)           
  H3    0.326346       0.538419       0.563908       0.024\*              
  C4    0.27987 (9)    0.38893 (12)   0.71028 (16)   0.0151 (2)           
  C5    0.31267 (10)   0.30049 (14)   0.83256 (18)   0.0202 (3)           
  H5    0.264213       0.240357       0.874761       0.024\*              
  C6    0.41732 (10)   0.30097 (14)   0.89257 (17)   0.0199 (3)           
  H6    0.440323       0.242335       0.977785       0.024\*              
  C7    0.60130 (10)   0.38109 (13)   0.88992 (17)   0.0185 (2)           
  ----- -------------- -------------- -------------- -------------------- ------------

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Atomic displacement parameters (Å^2^) {#d1e6693}
=====================================================================================================

  ----- -------------- -------------- -------------- --------------- --------------- ---------------
        *U*^11^        *U*^22^        *U*^33^        *U*^12^         *U*^13^         *U*^23^
  K1    0.01622 (10)   0.02482 (11)   0.01888 (11)   −0.00038 (7)    0.00068 (7)     −0.00163 (8)
  Ag1   0.01622 (10)   0.02482 (11)   0.01888 (11)   −0.00038 (7)    0.00068 (7)     −0.00163 (8)
  S1    0.01276 (13)   0.01278 (13)   0.02192 (17)   −0.00032 (10)   −0.00152 (11)   −0.00075 (11)
  O1    0.0136 (4)     0.0304 (5)     0.0319 (6)     −0.0033 (4)     −0.0024 (4)     0.0041 (4)
  O2    0.0194 (5)     0.0299 (5)     0.0315 (6)     0.0017 (4)      −0.0049 (4)     0.0061 (5)
  O3A   0.0183 (8)     0.0245 (11)    0.0199 (10)    0.0001 (7)      −0.0032 (6)     −0.0016 (8)
  O4A   0.0180 (8)     0.0289 (12)    0.0230 (13)    0.0065 (8)      0.0016 (8)      −0.0028 (9)
  O5A   0.0213 (8)     0.0176 (7)     0.0393 (17)    −0.0060 (5)     −0.0102 (11)    0.0077 (11)
  O6    0.0193 (4)     0.0183 (4)     0.0263 (5)     −0.0034 (4)     −0.0018 (4)     0.0002 (4)
  O7    0.0224 (5)     0.0235 (5)     0.0391 (7)     −0.0040 (4)     −0.0120 (5)     0.0060 (5)
  C1    0.0142 (5)     0.0155 (5)     0.0186 (6)     0.0009 (4)      0.0003 (4)      −0.0030 (5)
  C2    0.0156 (5)     0.0198 (6)     0.0233 (7)     −0.0038 (4)     0.0002 (5)      0.0027 (5)
  C3    0.0175 (6)     0.0184 (6)     0.0229 (7)     −0.0017 (5)     −0.0014 (5)     0.0049 (5)
  C4    0.0131 (5)     0.0132 (5)     0.0188 (6)     0.0004 (4)      −0.0001 (4)     −0.0021 (4)
  C5    0.0154 (6)     0.0198 (6)     0.0253 (7)     −0.0015 (4)     0.0021 (5)      0.0047 (5)
  C6    0.0165 (6)     0.0207 (6)     0.0221 (7)     0.0017 (5)      −0.0002 (5)     0.0046 (5)
  C7    0.0151 (5)     0.0186 (6)     0.0216 (7)     0.0008 (4)      −0.0005 (5)     −0.0050 (5)
  ----- -------------- -------------- -------------- --------------- --------------- ---------------

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Geometric parameters (Å, º) {#d1e7053}
===========================================================================================

  ------------------------- ------------- ------------------------ -------------
  K1---O7^i^                2.6233 (12)   O2---C7                  1.2167 (17)
  K1---O5A^ii^              2.649 (3)     O6---H6B                 0.838 (9)
  K1---O7                   2.7045 (13)   O6---H6A                 0.845 (9)
  K1---O4A^iii^             2.719 (3)     O7---H7B                 0.835 (9)
  K1---O6                   2.8017 (11)   O7---H7A                 0.840 (9)
  K1---O5A^iv^              2.968 (3)     C1---C2                  1.3903 (19)
  K1---O3A^iv^              3.004 (2)     C1---C6                  1.3949 (18)
  K1---O4A^ii^              3.239 (3)     C1---C7                  1.4970 (18)
  S1---O3B                  1.420 (13)    C2---C3                  1.3911 (18)
  S1---O5B                  1.437 (12)    C2---H2                  0.9500
  S1---O4A                  1.444 (3)     C3---C4                  1.3936 (18)
  S1---O3A                  1.462 (3)     C3---H3                  0.9500
  S1---O5A                  1.473 (3)     C4---C5                  1.3891 (19)
  S1---O4B                  1.523 (12)    C5---C6                  1.3918 (19)
  S1---C4                   1.7759 (12)   C5---H5                  0.9500
  O1---C7                   1.3203 (17)   C6---H6                  0.9500
  O1---H1                   0.79 (2)                               
                                                                   
  O7^i^---K1---O5A^ii^      82.22 (6)     O4B---S1---C4            105.2 (4)
  O7^i^---K1---O7           106.02 (4)    C7---O1---H1             109.5
  O5A^ii^---K1---O7         171.76 (6)    S1---O3A---K1^v^         95.06 (11)
  O7^i^---K1---O4A^iii^     76.03 (7)     S1---O4A---K1^vi^        120.42 (14)
  O5A^ii^---K1---O4A^iii^   91.56 (9)     S1---O4A---K1^vii^       87.91 (12)
  O7---K1---O4A^iii^        90.63 (6)     K1^vi^---O4A---K1^vii^   131.53 (9)
  O7^i^---K1---O6           75.15 (3)     S1---O5A---K1^vii^       112.98 (16)
  O5A^ii^---K1---O6         114.66 (7)    S1---O5A---K1^v^         96.27 (12)
  O7---K1---O6              68.29 (3)     K1^vii^---O5A---K1^v^    96.81 (9)
  O4A^iii^---K1---O6        137.38 (6)    K1---O6---H6B            100.6 (14)
  O7^i^---K1---O5A^iv^      169.20 (6)    K1---O6---H6A            127.7 (13)
  O5A^ii^---K1---O5A^iv^    96.70 (9)     H6B---O6---H6A           107.1 (19)
  O7---K1---O5A^iv^         75.18 (6)     K1^viii^---O7---K1       104.27 (4)
  O4A^iii^---K1---O5A^iv^   114.76 (8)    K1^viii^---O7---H7B      107.2 (15)
  O6---K1---O5A^iv^         95.76 (6)     K1---O7---H7B            91.6 (16)
  O7^i^---K1---O3A^iv^      139.67 (6)    K1^viii^---O7---H7A      131.1 (16)
  O5A^ii^---K1---O3A^iv^    71.31 (8)     K1---O7---H7A            109.9 (16)
  O7---K1---O3A^iv^         101.65 (6)    H7B---O7---H7A           106 (2)
  O4A^iii^---K1---O3A^iv^   74.89 (8)     C2---C1---C6             120.24 (12)
  O6---K1---O3A^iv^         143.56 (6)    C2---C1---C7             121.13 (12)
  O5A^iv^---K1---O3A^iv^    48.30 (8)     C6---C1---C7             118.63 (12)
  O7^i^---K1---O4A^ii^      85.68 (6)     C1---C2---C3             120.12 (12)
  O5A^ii^---K1---O4A^ii^    47.18 (8)     C1---C2---H2             119.9
  O7---K1---O4A^ii^         131.93 (6)    C3---C2---H2             119.9
  O4A^iii^---K1---O4A^ii^   137.14 (3)    C2---C3---C4             119.18 (12)
  O6---K1---O4A^ii^         70.37 (5)     C2---C3---H3             120.4
  O5A^iv^---K1---O4A^ii^    85.76 (8)     C4---C3---H3             120.4
  O3A^iv^---K1---O4A^ii^    97.16 (7)     C5---C4---C3             121.18 (12)
  O3B---S1---O5B            110.4 (6)     C5---C4---S1             119.30 (10)
  O4A---S1---O3A            112.75 (15)   C3---C4---S1             119.45 (10)
  O4A---S1---O5A            111.92 (17)   C4---C5---C6             119.25 (12)
  O3A---S1---O5A            112.73 (15)   C4---C5---H5             120.4
  O3B---S1---O4B            111.5 (5)     C6---C5---H5             120.4
  O5B---S1---O4B            110.2 (6)     C5---C6---C1             120.01 (13)
  O3B---S1---C4             109.0 (5)     C5---C6---H6             120.0
  O5B---S1---C4             110.3 (4)     C1---C6---H6             120.0
  O4A---S1---C4             105.94 (12)   O2---C7---O1             124.52 (12)
  O3A---S1---C4             106.77 (11)   O2---C7---C1             122.55 (12)
  O5A---S1---C4             106.12 (12)   O1---C7---C1             112.94 (12)
  ------------------------- ------------- ------------------------ -------------

Symmetry codes: (i) *x*, −*y*+1/2, *z*−1/2; (ii) *x*+1, *y*, *z*; (iii) −*x*+1, *y*−1/2, −*z*+3/2; (iv) *x*+1, −*y*+1/2, *z*+1/2; (v) *x*−1, −*y*+1/2, *z*−1/2; (vi) −*x*+1, *y*+1/2, −*z*+3/2; (vii) *x*−1, *y*, *z*; (viii) *x*, −*y*+1/2, *z*+1/2.

Potassium silver 4-carboxybenzenesulfonate salt dihydrate (IV). Hydrogen-bond geometry (Å, º) {#d1e7834}
=============================================================================================

  ------------------------- ---------- ---------- ------------- ---------------
  *D*---H···*A*             *D*---H    H···*A*    *D*···*A*     *D*---H···*A*
  O1---H1···O6              0.79       1.85       2.6328 (14)   168
  O6---H6*A*···O5*A*^vi^    0.85 (1)   2.01 (1)   2.840 (3)     168 (2)
  O6---H6*A*···O5*B*^vi^    0.85 (1)   2.01 (2)   2.819 (12)    159 (2)
  O6---H6*B*···O4*A*^ix^    0.84 (1)   1.99 (1)   2.824 (3)     176 (2)
  O6---H6*B*···O4*B*^ix^    0.84 (1)   1.82 (2)   2.643 (12)    168 (2)
  O7---H7*A*···O2           0.84 (1)   1.97 (1)   2.8111 (15)   177 (2)
  O7---H7*B*···O3*A*^iii^   0.84 (1)   2.03 (1)   2.838 (3)     162 (2)
  O7---H7*B*···O3*B*^iii^   0.84 (1)   1.87 (2)   2.650 (12)    155 (2)
  ------------------------- ---------- ---------- ------------- ---------------

Symmetry codes: (iii) −*x*+1, *y*−1/2, −*z*+3/2; (vi) −*x*+1, *y*+1/2, −*z*+3/2; (ix) −*x*+1, −*y*+1, −*z*+2.

![The mol­ecular structure of (I)[](#scheme1){ref-type="chem"}, showing the atom-numbering scheme. Displacement ellipsoids are shown at the 70% probability level and hydrogen atoms are shown as small spheres of arbitrary radii. Symmetry-equivalent water mol­ecules and the sulfonate O4 atom are included to show the complete coordination environment of the cation. The longer Jahn--Teller distorted Cu1---O4 distances are shown as hollow bonds. \[Symmetry code: (\#) 1 − *x*, 1 − *y*, −*z*.\]](e-75-01801-fig1){#fig1}

![The mol­ecular structure of (II)[](#scheme1){ref-type="chem"}, showing the atom-numbering scheme. Displacement ellipsoids are shown at the 70% probability level and hydrogen atoms are shown as small spheres of arbitrary radii. Only one of the disordered orientations of the arene ring (atoms C2*A*---C6*A* at 50% occupancy) is shown. Symmetry-equivalent water mol­ecules are included to show the complete coordination environment of the cation. The longer Jahn--Teller-distorted Cu1---O8 distances are shown as hollow bonds. \[Symmetry code: (\#) 1 − *x*, 2 − *y*, −*z*.\]](e-75-01801-fig2){#fig2}

![The mol­ecular structure of (III)[](#scheme1){ref-type="chem"}, showing the atom-numbering scheme. Displacement ellipsoids are shown at the 70% probability level and hydrogen atoms are shown as small spheres of arbitrary radii. Symmetry-equivalent oxygen atoms are included to show the complete coordination environments of the cations. Atoms Ag2 and K2 are present at 38% and 62% occupancies. The K2---O inter­actions are shown as hollow bonds for clarity. \[Symmetry codes: (\$) 1 − *x*, *y*,  − *z*; (&&) 1 − *x*, 1 − *y*, 1 − *z*; (@) 1 − *x*, 1 − *y*, 2 − *z*; (\#) *x*, 1 − *y*, *z* − ; (&) *x*, 1 − *y*, *z* + ; (@@) 1 − *x*, 1 − *y*, 2 − *z*; (\$\$) *x* + , *y* + , *z*; (\#\#)  − *x*, *y* + ,  − *z*.\]](e-75-01801-fig3){#fig3}

![The mol­ecular structure of (IV)[](#scheme1){ref-type="chem"}, showing the atom-numbering scheme. Displacement ellipsoids are shown at the 70% probability level and hydrogen atoms are shown as small spheres of arbitrary radii. Symmetry-equivalent water mol­ecules and sulfonate oxygen atoms are included to show the complete coordination environment of the cation. The minor disordered component of the sulfonate group (atoms O3*B*, O4*B*, and O5*B*) has been omitted for clarity. \[Symmetry codes: (\$) *x*,  − *y*, *z* − ; (&) 1 + *x*, *y*, *z*; (@) 1 + *x*, −*y* + , *z* + ; (\#) 1 − *x*, *y* − ,  − *z*.\]](e-75-01801-fig4){#fig4}

![Packing diagram of (I)[](#scheme1){ref-type="chem"} with the outline of the unit cell. View is onto the (010) plane. O---H⋯O hydrogen bonds connecting the layers of copper complexes are shown as dashed bonds. H atoms bonded to C atoms have been omitted. The longer Jahn--Teller-distorted Cu1---O4 distances are shown as hollow bonds. Displacement ellipsoids are drawn at the 70% probability level.](e-75-01801-fig5){#fig5}

![Partial packing diagram of (I)[](#scheme1){ref-type="chem"} showing a portion of the hydrogen-bonding scheme involving coordinated water mol­ecules O6 and O7, non-coordinated water mol­ecule O8, and the carb­oxy­lic acid group. Hydrogen bonds are shown as dashed bonds. The longer Jahn--Teller-distorted Cu1---O4 distances are shown as hollow bonds. Displacement ellipsoids are drawn at the 70% probability level. \[Symmetry codes: (\#) 1 − *x*, 1 − *y*, 1 − *z*; (&) *x* − 1, *y*, *z*.\]](e-75-01801-fig6){#fig6}

![Packing diagram of (II)[](#scheme1){ref-type="chem"} with the outline of the unit cell. View is onto the (010) plane. Only one of the disordered orientations of the arene rings (at 50% occupancy) is shown. O---H⋯O hydrogen bonds connecting the layers of hexa­aqua­copper complexes and 4-sulfo­benzoic acid anions are shown as dashed bonds. H atoms bonded to C atoms have been omitted. The longer Jahn--Teller-distorted Cu1---O8 distances are shown as hollow bonds. Displacement ellipsoids are drawn at the 70% probability level.](e-75-01801-fig7){#fig7}

![Packing diagram of (III)[](#scheme1){ref-type="chem"} with the outline of the unit cell. View is onto the (001) plane. The layers of 4-sulfo­benzoic acid anions are evident with the silver and potassium ions situated in between the layers. O---H⋯O hydrogen bonds connecting the carb­oxy­lic H atoms and carboxyl­ate O atoms of adjacent layers are shown as dashed bonds. H atoms bonded to C atoms have been omitted. Displacement ellipsoids are drawn at the 70% probability level.](e-75-01801-fig8){#fig8}

![Packing diagram of (IV)[](#scheme1){ref-type="chem"} with the outline of the unit cell. View is onto the (010) plane. The layers of 4-sulfo­benzoic acid anions are in the center of the cell with the silver and potassium ions (disordered over the same site) situated in between the layers. O---H⋯O hydrogen bonds between the carb­oxy­lic groups and coordinated water mol­ecules are shown as dashed bonds. H atoms bonded to C atoms have been omitted. Displacement ellipsoids are drawn at the 70% probability level.](e-75-01801-fig9){#fig9}

###### Hydrogen-bond geometry (Å, °) for (I)[](#scheme1){ref-type="chem"}

  *D*---H⋯*A*          *D*---H    H⋯*A*      *D*⋯*A*       *D*---H⋯*A*
  -------------------- ---------- ---------- ------------- -------------
  O1---H1⋯O8^i^        0.78       1.94       2.6979 (12)   164
  O6---H6*B*⋯O5^ii^    0.81 (1)   1.97 (1)   2.7738 (11)   172 (2)
  O6---H6*A*⋯O8^iii^   0.81 (1)   1.88 (1)   2.6872 (11)   172 (2)
  O7---H7*A*⋯O2^iv^    0.83 (1)   1.86 (1)   2.6845 (11)   171 (2)
  O7---H7*B*⋯O3^v^     0.84 (1)   1.84 (1)   2.6672 (11)   169 (2)
  O8---H8*B*⋯O7        0.82 (1)   2.17 (1)   2.9255 (11)   153 (2)
  O8---H8*A*⋯O5^ii^    0.83 (1)   1.99 (1)   2.7984 (11)   165 (2)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .

###### Hydrogen-bond geometry (Å, °) for (II)[](#scheme1){ref-type="chem"}

  *D*---H⋯*A*        *D*---H    H⋯*A*      *D*⋯*A*     *D*---H⋯*A*
  ------------------ ---------- ---------- ----------- -------------
  O1---H1⋯O8         0.86 (7)   1.83 (7)   2.677 (4)   170 (7)
  O6---H61⋯O5^i^     0.84 (2)   1.89 (3)   2.717 (4)   169 (5)
  O6---H62⋯O4^ii^    0.84 (2)   1.93 (3)   2.725 (5)   158 (5)
  O7---H71⋯O4^iii^   0.83 (2)   1.99 (3)   2.784 (5)   160 (5)
  O7---H72⋯O2        0.83 (2)   1.84 (3)   2.645 (4)   161 (5)
  O8---H81⋯O3^iv^    0.85 (2)   2.02 (3)   2.851 (5)   167 (5)
  O8---H82⋯O5^v^     0.84 (2)   2.02 (3)   2.854 (5)   175 (5)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) .

###### Hydrogen-bond geometry (Å, °) for (III)[](#scheme1){ref-type="chem"}

  *D*---H⋯*A*     *D*---H   H⋯*A*   *D*⋯*A*       *D*---H⋯*A*
  --------------- --------- ------- ------------- -------------
  O1---H1⋯O2^i^   0.75      1.94    2.6841 (16)   172

Symmetry code: (i) .

###### Hydrogen-bond geometry (Å, °) for (IV)[](#scheme1){ref-type="chem"}

  *D*---H⋯*A*              *D*---H    H⋯*A*      *D*⋯*A*       *D*---H⋯*A*
  ------------------------ ---------- ---------- ------------- -------------
  O1---H1⋯O6               0.79       1.85       2.6328 (14)   168
  O6---H6*A*⋯O5*A* ^i^     0.85 (1)   2.01 (1)   2.840 (3)     168 (2)
  O6---H6*A*⋯O5*B* ^i^     0.85 (1)   2.01 (2)   2.819 (12)    159 (2)
  O6---H6*B*⋯O4*A* ^ii^    0.84 (1)   1.99 (1)   2.824 (3)     176 (2)
  O6---H6*B*⋯O4*B* ^ii^    0.84 (1)   1.82 (2)   2.643 (12)    168 (2)
  O7---H7*A*⋯O2            0.84 (1)   1.97 (1)   2.8111 (15)   177 (2)
  O7---H7*B*⋯O3*A* ^iii^   0.84 (1)   2.03 (1)   2.838 (3)     162 (2)
  O7---H7*B*⋯O3*B* ^iii^   0.84 (1)   1.87 (2)   2.650 (12)    155 (2)

Symmetry codes: (i) ; (ii) ; (iii) .

###### Experimental details

                                                                             \(I\)                                                                    \(II\)                                                                   \(III\)                                                                  \(IV\)
  -------------------------------------------------------------------------- ------------------------------------------------------------------------ ------------------------------------------------------------------------ ------------------------------------------------------------------------ ------------------------------------------------------------------------
  Crystal data                                                                                                                                                                                                                                                                                          
  Chemical formula                                                           \[Cu(C~7~H~5~O~5~S)~2~(H~2~O)~4~\]·2H~2~O                                \[Cu(H~2~O)~6~\](C~7~H~5~O~5~S)~2~                                       \[Ag~0.69~K~0.31~\](C~7~H~5~O~5~S)                                       \[Ag~0.20~K~0.80~\](C~7~H~5~O~5~S)·2H~2~O
  *M* ~r~                                                                    573.97                                                                   573.97                                                                   287.72                                                                   290.06
  Crystal system, space group                                                Triclinic, *P*                                                           Triclinic, *P*                                                           Monoclinic, *C*2/*c*                                                     Monoclinic, *P*2~1~/*c*
  Temperature (K)                                                            130                                                                      130                                                                      120                                                                      120
  *a*, *b*, *c* (Å)                                                          6.1907 (1), 7.2010 (2), 12.4919 (3)                                      6.4380 (13), 7.2431 (14), 12.088 (2)                                     19.436 (3), 15.644 (3), 5.3355 (9)                                       12.8018 (7), 9.9170 (6), 8.4013 (5)
  α, β, γ (°)                                                                90.310 (1), 94.587 (1), 111.087 (1)                                      72.60 (3), 77.20 (3), 82.13 (3)                                          90, 95.651 (2), 90                                                       90, 94.747 (1), 90
  *V* (Å^3^)                                                                 517.57 (2)                                                               523.0 (2)                                                                1614.4 (5)                                                               1062.93 (11)
  *Z*                                                                        1                                                                        1                                                                        8                                                                        4
  Radiation type                                                             Mo *K*α                                                                  Mo *K*α                                                                  Mo *K*α                                                                  Mo *K*α
  μ (mm^−1^)                                                                 1.34                                                                     1.33                                                                     2.18                                                                     0.99
  Crystal size (mm)                                                          0.14 × 0.12 × 0.06                                                       0.21 × 0.08 × 0.02                                                       0.16 × 0.06 × 0.03                                                       0.23 × 0.17 × 0.07
                                                                                                                                                                                                                                                                                                        
  Data collection                                                                                                                                                                                                                                                                                       
  Diffractometer                                                             Bruker APEXII CCD                                                        Bruker APEXII CCD                                                        Bruker APEXII CCD                                                        Bruker APEXII CCD
  Absorption correction                                                      Multi-scan (*SADABS*; Krause *et al.*, 2015[@bb9])                       Multi-scan (*TWINABS*; Sheldrick, 1996[@bb16])                           Multi-scan (*SADABS*; Krause *et al.*, 2015[@bb9])                       Multi-scan (*SADABS*; Krause *et al.*, 2015[@bb9])
  *T* ~min~, *T* ~max~                                                       0.685, 0.747                                                             0.585, 0.747                                                             0.572, 0.648                                                             0.666, 0.746
  No. of measured, independent and observed \[*I* \> 2σ(*I*)\] reflections   13360, 3630, 3460                                                        3738, 3738, 3370                                                         12751, 2435, 2223                                                        16575, 3255, 2831
  *R* ~int~                                                                  0.011                                                                    0.045                                                                    0.020                                                                    0.023
  (sin θ/λ)~max~ (Å^−1^)                                                     0.767                                                                    0.766                                                                    0.712                                                                    0.716
                                                                                                                                                                                                                                                                                                        
  Refinement                                                                                                                                                                                                                                                                                            
  *R*\[*F* ^2^ \> 2σ(*F* ^2^)\], *wR*(*F* ^2^), *S*                          0.020, 0.057, 1.14                                                       0.059, 0.139, 1.18                                                       0.017, 0.043, 1.08                                                       0.025, 0.063, 1.08
  No. of reflections                                                         3630                                                                     3738                                                                     2435                                                                     3255
  No. of parameters                                                          171                                                                      169                                                                      135                                                                      171
  No. of restraints                                                          6                                                                        18                                                                       0                                                                        4
  H-atom treatment                                                           H atoms treated by a mixture of independent and constrained refinement   H atoms treated by a mixture of independent and constrained refinement   H atoms treated by a mixture of independent and constrained refinement   H atoms treated by a mixture of independent and constrained refinement
  Δρ~max~, Δρ~min~ (e Å^−3^)                                                 0.51, −0.43                                                              0.84, −1.19                                                              0.51, −0.36                                                              0.44, −0.54

Computer programs: *APEX3* and *SAINT* (Bruker, 2015[@bb1]), *SHELXT2018* (Sheldrick, 2015*a* [@bb18]), *SHELXL2017* (Sheldrick, 2015*b* [@bb19]), *CrystalMaker* (Palmer, 2014[@bb13]) and *CELL_NOW 2008/4* (Sheldrick, 2008[@bb17]).
