Related literature   {#sec1}
====================

For related bis-bidentate Schiff base ligand structures, see: Birkedal & Pattison (2006[@bb2]); Shahverdizadeh & Tiekink (2011[@bb9]). For Schiff base ligands, see: Chu & Huang (2007[@bb3]); Yoshida & Ichikawa, (1997[@bb14]); Kruger *et al.* (2001[@bb5]); Moutet & Ourari (1997[@bb7]). For applications of bis-bidentate Schiff base ligands, see: Lin *et al.* (2008[@bb6]); Sadeghi *et al.* (2003[@bb8]).

Experimental   {#sec2}
==============

 {#sec2.1}

### Crystal data   {#sec2.1.1}

C~29~H~26~N~2~O~4~*M* *~r~* = 466.52Monoclinic,*a* = 41.307 (4) Å*b* = 4.5993 (3) Å*c* = 12.2229 (13) Åβ = 93.653 (12)°*V* = 2317.4 (4) Å^3^*Z* = 4Mo *K*α radiationμ = 0.09 mm^−1^*T* = 293 K0.69 × 0.38 × 0.06 mm

### Data collection   {#sec2.1.2}

Stoe IPDS diffractometerAbsorption correction: gaussian (*ABSGAUSS* in *PLATON*; Spek, 2009[@bb11]) *T* ~min~ = 0.953, *T* ~max~ = 0.99310694 measured reflections2244 independent reflections1662 reflections with *I* \> 2σ(*I*)*R* ~int~ = 0.037

### Refinement   {#sec2.1.3}

*R*\[*F* ^2^ \> 2σ(*F* ^2^)\] = 0.039*wR*(*F* ^2^) = 0.116*S* = 1.062244 reflections160 parametersH-atom parameters constrainedΔρ~max~ = 0.17 e Å^−3^Δρ~min~ = −0.15 e Å^−3^

 {#d5e431}

Data collection: *EXPOSE* (Stoe & Cie, 1995[@bb12]); cell refinement: *X-RED* (Stoe & Cie, 1995[@bb12]); data reduction: *X-RED*; program(s) used to solve structure: *SIR92* (Altomare *et al.*, 1993[@bb1]); program(s) used to refine structure: *SHELXL97* (Sheldrick, 2008[@bb10]); molecular graphics: *ORTEP-3 for Windows* (Farrugia, 1997[@bb4]); software used to prepare material for publication: *publCIF* (Westrip, 2010[@bb13]).

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

Crystal structure: contains datablock(s) global, I. DOI: [10.1107/S1600536812010550/qk2024sup1.cif](http://dx.doi.org/10.1107/S1600536812010550/qk2024sup1.cif)

Structure factors: contains datablock(s) I. DOI: [10.1107/S1600536812010550/qk2024Isup2.hkl](http://dx.doi.org/10.1107/S1600536812010550/qk2024Isup2.hkl)

Additional supplementary materials: [crystallographic information](http://scripts.iucr.org/cgi-bin/sendsupfiles?qk2024&file=qk2024sup0.html&mime=text/html); [3D view](http://scripts.iucr.org/cgi-bin/sendcif?qk2024sup1&Qmime=cif); [checkCIF report](http://scripts.iucr.org/cgi-bin/paper?qk2024&checkcif=yes)

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: [QK2024](http://scripts.iucr.org/cgi-bin/sendsup?qk2024)).

The authors are very grateful to Professor Jean-Claude Daran at the Laboratoire de Chimie de Coordination, UPR-CNRS 8241 (Toulouse) for his valuable contribution and insightful discussions.

Comment
=======

Bis-bidentate Schiff base ligands have been extensively studied and used as building blocks in metallo-supramolecular chemistry (Birkedal & Pattison, 2006; Shahverdizadeh & Tiekink, 2011; Chu & Huang, 2007; Yoshida & Ichikawa, 1997; Kruger *et al.*, 2001). These compounds were also used as thermosetting resins (Lin *et al.*, 2008) and in ion selective membranes for detecting traces of copper (Sadeghi *et al.*, 2003). We were interested in such ligands owing to their diverse applications in coordination chemistry, catalysis and electrocatalysis (Moutet & Ourari, 1997).

The molecule of the title compound is arranged around the two fold axis at 1/2, *y*, 3/4 of the unit cell and methylene carbon C14 coinciding with it. The molecule is V-shaped and has a dihedral angle of 78.11 (4)° between the two inner phenyl rings. The phenyl and the 5-methoxysalicylidene rings are slightly twisted with respect to each other by a dihedral angle of 11.84 (8)°. There are two symmetry equivalent intramolecular O-H···N hydrogen bonds. The bond lengths and bond angles within the molecule agree well with those of the closely related compounds C~27~H~22~N~2~O~2~ (CCDC refcode YEFWUC; Birkedal & Pattison, 2006) and C~26~H~20~N~2~O~3~ (Shahverdizadeh & Tiekink, 2011). In the unit cell, the molecules are tightly stacked one above the other along the short *b-*axis (*b* = 4.5993 (3) Å) and are held together in this direction by slipped π-π stacking interactions between the phenyl rings and the iminomethylidene groups. The architecture and space group of the title structure is identical with CCDC YEFWUC.

Experimental {#experimental}
============

5-Methoxysalicyaldehyde (98%), 4, 4\'-diaminodiphenylmethane (97%), anhydrous ethanol were all purchased from Alfa aesar and used as received. 200 mg (1 mmol) of 4, 4\'-diaminodiphenylmethane were dissolved in 10 ml of absolute ethanol. To this solution, 304 mg (2 mmol) of 5-methoxysalicyaldehyde in 5 ml of absolute ethanol was dropwisely added under stirring. Then, this mixture was heated for 15 min at 50 °C. The resulting yellow precipitate was recovered by filtration, washed several times with a small portions of EtOH and then with diethyl ether to give 443 mg (95%) of the title compound. Suitable crystals were obtained by slow evaporation of a solution in dichloromethane/ethanol (9/1, v /v).

Refinement {#refinement}
==========

All H atoms attached to C were fixed geometrically and treated as riding with C---H = 0.96 Å (methyl), 0.92 Å (methylene) or 0.93 Å (aromatic) with *U*~iso~(H) = 1.2*U*~eq~(C) or *U*~iso~(H) = 1.5*U*~eq~(methyl). The H atom of the hydroxyl group was initially refined using a soft restraint O---H = 0.89 (1) Å and *U*~iso~(H) = 1.2*U*~eq~(O). Then, in the last cycles of refinement, it was treated as riding on its parent O atom.

Figures
=======

![A molecule of the title compound with the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are represented as small spheres of arbitrary radii. Hydrogen bonds are shown as dashed lines. \[Symmetry code: (i) -x + 1, y, -z + 3/2\]](e-68-o1141-fig1){#Fap1}

Crystal data {#tablewrapcrystaldatalong}
============

  ----------------------- ---------------------------------------
  C~29~H~26~N~2~O~4~      *F*(000) = 984
  *M~r~* = 466.52         *D*~x~ = 1.337 Mg m^−3^
  Monoclinic, *C*2/*c*    Mo *K*α radiation, λ = 0.71073 Å
  Hall symbol: -C 2yc     Cell parameters from 8000 reflections
  *a* = 41.307 (4) Å      θ = 2.0--25.9°
  *b* = 4.5993 (3) Å      µ = 0.09 mm^−1^
  *c* = 12.2229 (13) Å    *T* = 293 K
  β = 93.653 (12)°        Plate, yellow
  *V* = 2317.4 (4) Å^3^   0.69 × 0.38 × 0.06 mm
  *Z* = 4                 
  ----------------------- ---------------------------------------

Data collection {#tablewrapdatacollectionlong}
===============

  ----------------------------------------------------------------- --------------------------------------
  Stoe IPDS diffractometer                                          2244 independent reflections
  Radiation source: normal-focus sealed tube                        1662 reflections with *I* \> 2σ(*I*)
  Graphite monochromator                                            *R*~int~ = 0.037
  Detector resolution: 6.66 pixels mm^-1^                           θ~max~ = 25.8°, θ~min~ = 2.0°
  0.6° φ scans                                                      *h* = −50→50
  Absorption correction: gaussian (*PLATON*-ABSGAUSS; Spek, 2009)   *k* = −5→5
  *T*~min~ = 0.953, *T*~max~ = 0.993                                *l* = −14→15
  10694 measured reflections                                        
  ----------------------------------------------------------------- --------------------------------------

Refinement {#tablewraprefinementdatalong}
==========

  ------------------------------------- ------------------------------------------------------------------------------------------------
  Refinement on *F*^2^                  Primary atom site location: structure-invariant direct methods
  Least-squares matrix: full            Secondary atom site location: difference Fourier map
  *R*\[*F*^2^ \> 2σ(*F*^2^)\] = 0.039   Hydrogen site location: inferred from neighbouring sites
  *wR*(*F*^2^) = 0.116                  H-atom parameters constrained
  *S* = 1.06                            *w* = 1/\[σ^2^(*F*~o~^2^) + (0.072*P*)^2^ + 0.1658*P*\] where *P* = (*F*~o~^2^ + 2*F*~c~^2^)/3
  2244 reflections                      (Δ/σ)~max~ = 0.001
  160 parameters                        Δρ~max~ = 0.17 e Å^−3^
  0 restraints                          Δρ~min~ = −0.15 e Å^−3^
  ------------------------------------- ------------------------------------------------------------------------------------------------

Special details {#specialdetails}
===============

  -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
  Geometry. All e.s.d.\'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.\'s are taken into account individually in the estimation of e.s.d.\'s in distances, angles and torsion angles; correlations between e.s.d.\'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.\'s is used for estimating e.s.d.\'s involving l.s. planes.
  Refinement. Refinement of *F*^2^ against ALL reflections. The weighted *R*-factor *wR* and goodness of fit *S* are based on *F*^2^, conventional *R*-factors *R* are based on *F*, with *F* set to zero for negative *F*^2^. The threshold expression of *F*^2^ \> σ(*F*^2^) is used only for calculating *R*-factors(gt) *etc*. and is not relevant to the choice of reflections for refinement. *R*-factors based on *F*^2^ are statistically about twice as large as those based on *F*, and *R*- factors based on ALL data will be even larger.
  -----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å^2^) {#tablewrapcoords}
==================================================================================================

  ------ ------------- ------------- -------------- -------------------- --
         *x*           *y*           *z*            *U*~iso~\*/*U*~eq~   
  O1     0.37635 (3)   0.9988 (3)    0.40329 (8)    0.0634 (3)           
  H1     0.3881        0.8694        0.4423         0.076\*              
  O2     0.28937 (3)   1.4522 (3)    0.68223 (9)    0.0651 (4)           
  N1     0.40032 (2)   0.7019 (2)    0.57231 (8)    0.0404 (3)           
  C1     0.35488 (3)   1.1095 (3)    0.47152 (10)   0.0435 (3)           
  C2     0.33158 (3)   1.3024 (4)    0.43070 (11)   0.0521 (4)           
  H2     0.3309        1.3538        0.3570         0.063\*              
  C3     0.30928 (3)   1.4206 (3)    0.49763 (12)   0.0502 (4)           
  H3     0.2936        1.5494        0.4687         0.060\*              
  C4     0.31021 (3)   1.3469 (3)    0.60828 (11)   0.0451 (3)           
  C5     0.33363 (3)   1.1561 (3)    0.64977 (11)   0.0438 (3)           
  H5     0.3345        1.1092        0.7239         0.053\*              
  C6     0.35595 (3)   1.0324 (3)    0.58312 (10)   0.0377 (3)           
  C7     0.26320 (4)   1.6273 (4)    0.64047 (16)   0.0725 (5)           
  H7A    0.2715        1.8012        0.6091         0.109\*              
  H7B    0.2498        1.6779        0.6989         0.109\*              
  H7C    0.2506        1.5214        0.5851         0.109\*              
  C8     0.37983 (3)   0.8291 (3)    0.63036 (10)   0.0405 (3)           
  H8     0.3803        0.7902        0.7051         0.049\*              
  C9     0.42351 (3)   0.5050 (3)    0.62024 (10)   0.0381 (3)           
  C10    0.42235 (3)   0.3824 (3)    0.72409 (11)   0.0460 (3)           
  H10    0.4053        0.4280        0.7673         0.055\*              
  C11    0.44638 (3)   0.1933 (3)    0.76319 (11)   0.0463 (3)           
  H11    0.4450        0.1111        0.8323         0.056\*              
  C12    0.47241 (3)   0.1226 (3)    0.70280 (11)   0.0411 (3)           
  C13    0.47310 (3)   0.2425 (3)    0.59852 (12)   0.0489 (4)           
  H13    0.4902        0.1979        0.5556         0.059\*              
  C14    0.44889 (3)   0.4265 (3)    0.55754 (11)   0.0467 (4)           
  H14    0.4496        0.4989        0.4867         0.056\*              
  C15    0.5000        −0.0659 (4)   0.7500         0.0474 (5)           
  H15A   0.4922        −0.1658       0.8076         0.057\*              
  ------ ------------- ------------- -------------- -------------------- --

Atomic displacement parameters (Å^2^) {#tablewrapadps}
=====================================

  ----- ------------- ------------- ------------- ------------- ------------- -------------
        *U*^11^       *U*^22^       *U*^33^       *U*^12^       *U*^13^       *U*^23^
  O1    0.0703 (7)    0.0835 (8)    0.0375 (5)    0.0297 (6)    0.0109 (5)    0.0061 (5)
  O2    0.0592 (6)    0.0793 (8)    0.0583 (6)    0.0268 (6)    0.0149 (5)    0.0052 (6)
  N1    0.0401 (5)    0.0405 (6)    0.0402 (6)    0.0025 (5)    −0.0008 (4)   −0.0006 (5)
  C1    0.0460 (7)    0.0490 (8)    0.0353 (6)    0.0034 (6)    0.0015 (5)    −0.0016 (6)
  C2    0.0586 (8)    0.0599 (10)   0.0372 (7)    0.0101 (7)    −0.0021 (6)   0.0062 (6)
  C3    0.0472 (7)    0.0528 (9)    0.0496 (8)    0.0094 (6)    −0.0055 (6)   0.0050 (6)
  C4    0.0417 (6)    0.0468 (8)    0.0471 (7)    0.0038 (6)    0.0050 (6)    −0.0013 (6)
  C5    0.0463 (7)    0.0481 (8)    0.0370 (6)    0.0028 (6)    0.0029 (5)    0.0038 (6)
  C6    0.0387 (6)    0.0378 (7)    0.0363 (6)    −0.0012 (5)   −0.0011 (5)   −0.0008 (5)
  C7    0.0619 (10)   0.0752 (12)   0.0819 (12)   0.0267 (9)    0.0173 (9)    0.0054 (10)
  C8    0.0444 (7)    0.0419 (8)    0.0348 (6)    0.0008 (6)    −0.0003 (5)   0.0013 (5)
  C9    0.0380 (6)    0.0358 (7)    0.0399 (6)    −0.0009 (5)   −0.0026 (5)   −0.0017 (5)
  C10   0.0411 (7)    0.0519 (9)    0.0451 (7)    0.0042 (6)    0.0050 (5)    0.0047 (6)
  C11   0.0462 (7)    0.0477 (8)    0.0444 (7)    −0.0017 (6)   −0.0020 (6)   0.0080 (6)
  C12   0.0393 (7)    0.0312 (7)    0.0516 (7)    −0.0039 (5)   −0.0059 (5)   −0.0040 (6)
  C13   0.0471 (7)    0.0487 (9)    0.0515 (8)    0.0076 (6)    0.0075 (6)    −0.0037 (6)
  C14   0.0518 (7)    0.0485 (9)    0.0401 (7)    0.0070 (6)    0.0055 (6)    0.0015 (6)
  C15   0.0445 (10)   0.0342 (11)   0.0626 (12)   0.000         −0.0055 (9)   0.000
  ----- ------------- ------------- ------------- ------------- ------------- -------------

Geometric parameters (Å, º) {#tablewrapgeomlong}
===========================

  ------------------- ------------- --------------------- -------------
  O1---C1             1.3548 (15)   C7---H7B              0.9600
  O1---H1             0.8879        C7---H7C              0.9600
  O2---C4             1.3754 (16)   C8---H8               0.9300
  O2---C7             1.4168 (19)   C9---C14              1.3852 (17)
  N1---C8             1.2802 (16)   C9---C10              1.3926 (18)
  N1---C9             1.4176 (16)   C10---C11             1.3822 (19)
  C1---C2             1.379 (2)     C10---H10             0.9300
  C1---C6             1.4074 (18)   C11---C12             1.3814 (18)
  C2---C3             1.3819 (19)   C11---H11             0.9300
  C2---H2             0.9300        C12---C13             1.3908 (19)
  C3---C4             1.392 (2)     C12---C15             1.5161 (17)
  C3---H3             0.9300        C13---C14             1.3795 (19)
  C4---C5             1.3787 (19)   C13---H13             0.9300
  C5---C6             1.3901 (18)   C14---H14             0.9300
  C5---H5             0.9300        C15---C12^i^          1.5161 (17)
  C6---C8             1.4520 (18)   C15---H15A            0.9160
  C7---H7A            0.9600                              
                                                          
  C1---O1---H1        106.2         H7B---C7---H7C        109.5
  C4---O2---C7        117.30 (12)   N1---C8---C6          122.03 (12)
  C8---N1---C9        121.08 (11)   N1---C8---H8          119.0
  O1---C1---C2        119.22 (12)   C6---C8---H8          119.0
  O1---C1---C6        121.38 (12)   C14---C9---C10        118.04 (12)
  C2---C1---C6        119.40 (12)   C14---C9---N1         116.95 (11)
  C1---C2---C3        121.01 (13)   C10---C9---N1         125.00 (11)
  C1---C2---H2        119.5         C11---C10---C9        120.28 (12)
  C3---C2---H2        119.5         C11---C10---H10       119.9
  C2---C3---C4        120.06 (13)   C9---C10---H10        119.9
  C2---C3---H3        120.0         C12---C11---C10       122.00 (13)
  C4---C3---H3        120.0         C12---C11---H11       119.0
  O2---C4---C5        115.87 (12)   C10---C11---H11       119.0
  O2---C4---C3        124.94 (13)   C11---C12---C13       117.28 (12)
  C5---C4---C3        119.19 (12)   C11---C12---C15       121.54 (11)
  C4---C5---C6        121.39 (12)   C13---C12---C15       121.11 (11)
  C4---C5---H5        119.3         C14---C13---C12       121.29 (12)
  C6---C5---H5        119.3         C14---C13---H13       119.4
  C5---C6---C1        118.95 (12)   C12---C13---H13       119.4
  C5---C6---C8        119.31 (11)   C13---C14---C9        121.04 (13)
  C1---C6---C8        121.75 (11)   C13---C14---H14       119.5
  O2---C7---H7A       109.5         C9---C14---H14        119.5
  O2---C7---H7B       109.5         C12^i^---C15---C12    110.27 (15)
  H7A---C7---H7B      109.5         C12^i^---C15---H15A   106.7
  O2---C7---H7C       109.5         C12---C15---H15A      106.6
  H7A---C7---H7C      109.5                               
                                                          
  C6---C8---N1---C9   179.75 (11)                         
  ------------------- ------------- --------------------- -------------

Symmetry code: (i) −*x*+1, *y*, −*z*+3/2.

Hydrogen-bond geometry (Å, º) {#tablewraphbondslong}
=============================

  --------------- --------- --------- ------------- ---------------
  *D*---H···*A*   *D*---H   H···*A*   *D*···*A*     *D*---H···*A*
  O1---H1···N1    0.89      1.81      2.6177 (15)   151
  --------------- --------- --------- ------------- ---------------

###### Hydrogen-bond geometry (Å, °)

  *D*---H⋯*A*   *D*---H   H⋯*A*   *D*⋯*A*       *D*---H⋯*A*
  ------------- --------- ------- ------------- -------------
  O1---H1⋯N1    0.89      1.81    2.6177 (15)   151
