Structural and spectroscopic studies of three novel two- and three-dimensional coordination polymers with benzenetricarboxylate ligands

Abstract

The synthesis, crystalline structure and vibrational characterisation of three new complexes with benzenetricarboxylate ligands are described in this work. Compound 1 {Na5[Cu3(C9H3O6)3(C9H4O6)(H2O)10)]·(H2O)3} was synthesised from 1,2,3-benzenetricarboxylic acid. This complex crystallised in a triclinic non-centrosymmetric space group (P1), and a three-dimensional coordination polymer was formed. This polymer displays an 8-connected uninodal net with the short Schläfli symbols (42464). Conversely, compounds 2 {[CoK2(C9H4O6)2(H2O)6]} and 3 {[Zn2(C9H4O6)2(H2O)6]} were synthesised from 1,2,4-benzenetricarboxylic (4-btc). These complexes crystallised in the triclinic centrosymmetric group P1¯, and, in both cases, two-dimensional coordination polymers were observed by X-ray diffraction. Compound 2 forms a 6,7-connected binodal net with the short Schläfli symbols (394953)2(3642566). A 4,6-connected binodal net is also observed for compound 3, and it presents Schläfli symbols equal to (324252)(34445463). In the infrared spectra, characteristic bands were observed at 1615 and 1459cm−1 for 1, at 1615 and 1264cm−1 for 2 and at 1592 and 1260cm−1 for 3 arising from the anti-symmetric and symmetric stretching modes of the carboxyl group (COO−), respectively. The difference between these frequencies suggests that the metal coordination mode in the complexes is monodentate, which agrees well with the X-ray diffraction data.