An insight into the non-covalent Cl•••Cl interaction in the solid state structure of carboxylate bridged trinuclear mixed valence cobalt(III/II/III) complexes with tetradentate N2O2 donor reduced Schiff base ligands

Two mixed-valence trinuclear cobalt(III)-cobalt(II)-cobalt(III) complexes, [CoII{(mu-L1)(mu-OOCC6H5NO2) CoIII(N3)}2] (1) and [CoII{(mu-L2)(mu-OOCC6H4NO2CH3)CoIII(N3}2] (2) have been synthesized using two tetradentate N2O2 donor 'reduced Schiff base' ligands, H2L1 {2,2-dimethyl-1,3-propanediyl)bis(iminomethylene)bis (4-chlorophenol}, and H2L2{2-hydroxy-1,3-propanediyl)bis(iminomethylene)bis(4-chlorophenol}, and 3-nitrobenzoic benzoic acid or 4-methyl 3-nitrobenzoic benzoic acid as anionic co-ligands. The complexes have been characterized by spectroscopic measurements and their solid state structures have been determined by single crystal X-ray diffraction analysis. The trinuclear cobalt(III)-cobalt(II)-cobalt(III) skeleton of both the complexes are linear and centrosymmetric. Both the central cobalt(II) and terminal cobalt(III) of both the complexes are hexa-coordinated. DFT calculations have been used to analysed some supramolecular assemblies of the complex that have been observed in the solid state, specifically the Cl & sdot;& sdot;& sdot;Cl interactions that result in the creation of a stable 2D supramolecular assembly in the solid state. QTAIM and NCI Plot computational tools have been used to characterize the interactions. Thermo-gravimetric (TG) analysis was used to examine the thermal behaviour of both complexes. The redox behaviors of both the complexes were studied by using Cyclic Voltammetry (CV).