Anion influence in the structural diversity of cadmium coordination polymers constructed from a pyridine based Schiff base ligand

A series of seven coordination polymers based on Cd and potentially tetradentate pyridine based Schiff base ligand with different anions (CH3COO, NO2 , Cl, I, N3 , SCN), [Cd(L)(CH3COO)(OH2)]n (1),{[Cd2 (L)2(NO2)2(CH3OH)2]CH3OH}n (2), {[Cd2(L)2Cl2(CH3OH)2]CH3OH}n (3), [Cd(HL)I2]n (4), [Cd3(L)2(N3)4]n (5), [Cd(L)(SCN)(OH2)]n (6) and [Cd(HL)(SCN)2]n (7) {HL = 2-pyridinecarbaldehyde isonicotinoyl hydrazone (HPCIH)} in order to rationalize the effect of the anion, have been synthesized and characterized by elemental analyses, FT-IR spectroscopy, single crystal X-ray data diffraction, etc. The results show the influence of the counter-ions on the coordination mode of the cadmium ion that is capable of forming compounds with five-, six- and seven-coordination numbers. The ligand acts as a negatively charged tetradentate N3O-donor ligand and coordinates to the cadmium center in the enolic form (@NAN@CAO) in 1–3 and 5–6 while in compounds 4 and 7 coordinates as N3- and N3O-donor neutral ligand in keto form (@NANHAC@O), respectively. Cadmium centers in 1–4 and 6, bridging by the HPCIH ligand cause to form one-dimensional coordination polymers and the anions act as terminal ligands. In compounds 5 and 7, the N3 and SCN also act as bridging ligands to the metal centers, and form 3D and 2D metal–organic polymers respectively. 2014 El