Different topology of mixed valence CoIICoIII complexes with SCN anions and hydrazone-pyridine-based ligands

Two novel mixed valence CoIICoIII complexes [Co4II(SCN)12(EtOH)2Co4III(L1)8] (1) and [CoII(SCN)2Co2III(L2)4]n (2) (HL1 = N'-(1-(pyridin-2-yl)ethylidene)nicotinohydrazide and HL2 = N'-(phenyl(pyridin-2-yl)methylene)isonicotinohydrazide) have been synthesized and structurally characterized by the single crystal X-ray crystallography. In both cases, the deprotonated ligands HL1 and HL2 behave as chelating species toward CoIII, further connecting CoII fragments through the nicotine pyridine donors. A different topology is observed in the solid state of these complexes, complex 1 being an octanuclear cyclic species, while 2 is a 1D coordination polymer. The DFT calculations followed by the topological analysis of the electron density distribution have shown the existence of interesting non-covalent S<middle dot><middle dot><middle dot>pi-system interactions in 1. The CSD database search for similar supramolecular motif involving NCS anion has shown that the number and strength of S<middle dot><middle dot><middle dot>pi interactions depend both on acidity of metal cation and number aromatic systems in the molecular structure of ligand.