Synthesis, X-ray characterization, DFT calculations and Hirshfeld surface analysis of thiosemicarbazone complexes of Mn+ ions (n=2, 3; M = Ni, Cd, Mn, Co and Cu)

Two new pyridine-based heterocyclic thiosemicarbazone ligands and their Ni(II), Cd(II), Mn(II), Co(III) and Cu(II) complexes have been synthesized and characterized by structural, analytical and spectroscopic methods. The monodeprotonated anionic forms of the ligands coordinate in a tridentate fashion via two nitrogen and one sulphur donor atoms to yield seven complexes in which metal centres vary from four-coordinated square planar to six-coordinated distorted octahedral geometries. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending on the anion coordinated to the metal centre. We have analysed the interesting supramolecular assemblies observed in the solid state of some complexes by means of DFT calculations. These assemblies are formed by a combination of several noncovalent interactions, including chelate ring-pi, pi-pi, and chalcogen bonding interactions, that have been characterized using Bader's Theory of atoms-in-molecules.