Cobalt dipicolinate complexes with nicotinamide and isonicotinamide ligands: Syntheses, crystal structures, spectroscopic, thermal and voltammetric studies

Two new dipicolinate complexes of cobalt, [Co(dpc)(na)(H2O)2]·H2O (1) and [Co(dpc)(ina)(H2O)2] (2) [dpc is dipicolinate or pyridine-2,6-dicarboxylate, na is nicotinamide and ina is isonicotinamide], have been prepared and characterized by thermal analysis, IR spectroscopy and X-ray diffraction techniques. The complex (1) crystallizes in triclinic system, whereas the complex (2) crystallizes in monoclinic system. The Co(II) ion in both complexes is bonded to dpc ligand through pyridine N atom together with one O atom of each carboxylate group, two aqua ligands and N pyridine atom of na (1) or ina (2), forming the distorted octahedral geometry. The complex molecules (1) and (2) are connected via NH⋯O and OH⋯O hydrogen bonds. The voltammetric behaviour of complexes (1) and (2) was also investigated in DMSO (dimethylsulfoxide) solution by cyclic voltammetry using n-Bu4NClO4 supporting electrolyte. The complexes exhibit only metal centered electroactivity in the potential ±1.25 V versus Ag/AgCl reference electrode.