Cobalt(II) and strontium(II) complexes of three isomers, nicotinamide, isonicotinamide and picolinamide

Novel coordination structures formed by cobalt(II) and strontium(II) complexes with nicotinamide (na), isonicotinamide (ina) and picolinamide (pa) are reported. The structures of these complexes (CoCl2·(C6H6N2O)2·6H2O (Co-na), CoCl2·(C6H6N2O)2 (Co-ina), CoCl2·(C6H6N2O)2·2H2O, (Co-pa), SrCl2·(C6H6N2O)2·4H2O (Sr-na), SrCl2·(C6H6N2O)2·3H2O (Sr-ina) and SrCl2·C6H6N2O·H2O (Sr-pa)) in the solid state have been characterized by X-ray single crystal diffraction, FTIR, FIR, THz, Raman and UV–Vis spectroscopies. Pyridyl nitrogen of nicotinamide is coordinated to Co2+, but pyridyl nitrogen and carbonyl oxygen are used for coordination to Sr2+, and each Sr2+ is coordinated to four ligands. For isonicotinamide, pyridyl nitrogen is coordinated to Co2+, carbonyl oxygen is coordinated to Sr2+ and the ligand is also hydrogen-bonded in Sr-ina. Pyridyl nitrogen and carbonyl oxygen of picolinamide are coordinated to Co2+ to form a five-membered ring structure, but the carbonyl oxygen is coordinated to two Sr2+ ions in Sr-pa. Some of the complexes can form chain or network structures. The experiments results indicate the differences of the coordination of Co and Sr ions, the changes of hydrogen bonds and conformation of the ligands induced by complexation.