Structural variations in self-assembled cadmium benzoate complexes

Abstract

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 La=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(La)(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(La)] such as R=4-NO2 (6), 4-Cl (7), and 1-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 4.138Å, and 3.748Å. The 1-naphthoate complex having pyridine has composition [Cd(L)2(Lb)2](H2O)] (9) where Lb=pyridine and L=1-naphthoate has seven co-ordination with a distorted pentagonal bipyramid geometry.