Acta Cryst. (2008). E64, m1208-m1209  [ doi:10.1107/S1600536808027347 ]

2,6-Diaminopyridinium bis(4-hydroxypyridine-2,6-dicarboxylato-³O²,N,O⁶)chromate(III) dihydrate

H. Aghabozorg, L. Roshan, N. Firoozi, M. Ghadermazi and S. Bagheri

Abstract: The reaction of chromium(III) nitrate hexahydrate, pyridine-2,6-diamine and 4-hydroxypyridine-2,6-dicarboxylic acid in a 1:2:2 molar ratio in aqueous solution resulted in the formation of the title compound, (C₅H₈N₃)[Cr(C₇H₃NO₅)₂]·2H₂O or (pydaH)[Cr(hypydc)₂]·2H₂O (where pyda is pyridine-2,6-diamine and hypydcH₂ is 4-hydroxypyridine-2,6-dicarboxylic acid). Each Cr^III atom is hexacoordinated by four O and two N atoms from two (hypydc)^2- fragments, which act as tridentate ligands, in a distorted octahedral geometry. The O-Cr-O-C torsion angles between the two planes of the (hypydc)^2- fragments [-99.81 (17) and 97.77 (17)°] indicate that these two units are almost perpendicular to one another. In the crystal structure, extensive O-HO, N-HO and C-HO hydrogen bonds with DA distances ranging from 2.560 (2) to 3.279 (3) Å, ion pairing, C-O [O = 3.166 (2) Å] and - stacking interactions between (hypydc)^2- and (pydaH)⁺ rings [with a centroid-centroid distance of 3.3353 (14) Å] contribute to the formation of a three-dimensional supramolecular structure.

Online 30 August 2008

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