Heteronuclear cobalt(III)/sodium complexes with salen type compartmental Schiff base ligands: methylene spacer regulated variation in nuclearity

Three heteronuclear cobalt(III)/sodium Schiff base complexes have been synthesized and characterized by elemental and spectral analysis. The structures of all three complexes have been confirmed by single crystal X-ray analyses. Each of these three complexes crystallizes in monoclinic space group P2(1)/c. In each complex, cobalt(III) is placed in the inner N2O2 compartment and sodium is placed in the outer O2O'(2) compartment (O and O' denote the phenolic and ethoxy/methoxy oxygen atoms, respectively) of the Schiff bases. With decrease in steric hindrance around the O2O'(2) compartment by the replacement of ethyl groups with methyl groups, tetranuclear complexes resulted instead of dinuclear ones. Interesting carbon bonding interactions in the solid state of the complexes have been studied by means of DFT calculations using several computational tools such as atoms-in-molecules (AIM) and natural bond orbital (NBO) analyses.