Structural variations in self-assembled cadmium benzoate complexes

A series of mixed ligand cadmium(II) complexes having 3,5-dimethylpyrazole and aromatic carboxylate are structurally characterized. The effect of substituent on aromatic ring and also the effect of composition on co-ordination behavior of these complexes are ascertained. Hydrogen bonded self-assembled mononuclear complexes are obtained from composition [Cd(L)2(La)2] where L. = 3,5-dimethylpyrazole L = R-C6H4COO- [R = H (1), 2-Cl (2), 4-OH (3), 2-OH (4)]. The cadmium complex (5) having composition [Cd(L)2(L.)(H2O)] (L = 2-NO2-C6H4COO-) is tetra-nuclear. The complex has eight and six co-ordination around cadmium and self-assembles through hydrogen bonding leading to form extended chain structure. The four complexes (1-4) have six co-ordinated trigonal prismatic geometry around cadmium ions. Cadmium complexes having composition [Cd(L)2(L,)] such as R = 4-NO2 (6), 4-Cl (7), and I naphthoate complex (8) are co-ordination polymers with seven co-ordination geometry around cadmium. In these co-ordination polymers different Cd-Cd distances are observed for alternate pair of cadmium ions. For example in the case of the co-ordination polymer of 4-nitro-benzoate complex the Cd-Cd distance between alternate pairs are 4.138 A, and 3.748 A. The 1-naphthoate complex having pyridine has composition [Cd(L)(2)(Lb)(2)](H2O)] (9) where L-b = pyridine and L = 1-naphthoate has seven co-ordination with a distorted pentagonal bipyramid geometry. (C) 2007 Elsevier Ltd. All rights reserved.