Structure and spectroscopic properties of bis(1-carboxyethyl-3-aminopyridinium) hydrobromide monohydrate
The structure of bis(1-carboxyethyl-3-aminopyridinium) hydrobromide monohydrate, (3-NH 2 PB2) 2 HBr⋅H 2 O ( 1 ), has been studied by X-ray diffraction, B3LYP/6-311G(d,p) calculations, FTIR and NMR spectroscopy and calorimetric measurements. The compound crystallizes in orthorhombic, space group P bca. The Br anion and water molecules are positionally disordered so that Br(1) and O(1w) are located at the same positions with the same average occupations and they form O(1w)H⋯Br bonded zigzag chains along [1 0 0], with the Br⋯O(1w)⋯Br and O(1w)⋯Br⋯O(1w) angles equal 121.0(3)°. These chains are connected to the O(1)⋯H(1)⋯O(11) bonded cations through NH⋯Br and NH⋯O(1w) bonds. A pair of 3-NH 2 PB2 molecules is bridged by a short symmetric O(1)·H·O(11) hydrogen bond of 2.462(6) Ǻ. The FTIR spectrum of ( 1 ) shows a broad and intense absorption in the 1500–400 cm −1 range, similar to that in the spectra of type A acid salts of carboxylic acids and other 2:1 betaine complexes with mineral acids. The assignment of the anharmonic experimental solid-state vibrational frequencies of the compound investigated is proposed based on the second-derivative spectrum ( d 2 ). Correlations between the experimental 13 C and 1 H NMR chemical shifts ( δ exp ) and the GIAO/B3LYP/6-311G(d,p) calculated magnetic isotropic shielding constants ( σ cal ) in DMSO-d 6 , δ exp = a + b · σ calc , are reported.