Four and six-coordinated cobalt complexes based on thiosemicarbazone. Formation, experimental and theoretical characterization

•Thiosemicarbazone-based three new complexes having Co2+ and Co3+ nuclei were obtained.•The structures of the complexes were explicated by experimental and theoretical methods.•The reaction using only the thiosemicarbazone gave a cobalt(II) complex.•Using pyridine or 2-aminopyridine as co-ligands, novel cobalt(III) complexes were gained.•According to calculations, the complexes are usable structures for NLO applications.