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 P2₁/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.

A mixed valence cobalt(III/II) complex, [(μ_1,3-OAc)₂{(SCN)Co^III(L¹)}₂Co^II]·H₂O (1), and an ionic coordination complex of cobalt(III), [Co^III(L²)₂][Co^III(L²)(N₃)₃] (2), have been synthesized and characterized {H₂L¹ = N,N′-bis(5-bromosalicylidene)-2,2-dimethyl-1,3-propanediamine and HL² = N(5-bromosalicylidene)-2,2-dimethyl-1,3-propanediamine}. Energetic features of the supramolecular interactions involved in both complexes have been studied through DFT calculations, which indicate that the trinuclear structure of complex 1 has been stabilized via σ-hole halogen bonding interactions in the solid state. On the other hand, counterintuitive anion⋯anion interactions are present in the solid state structure of complex 2, which have been stabilized through anti-electrostatic H-bonds (AEHB). The dissociation scan plot for the AEHB dimer has showed the existence of a significantly high energetic barrier.

A hetero-dinuclear cobalt( iii )/sodium complex has been synthesized and characterized. The complex which has been used to construct photosensitive Schottky devices, shows interesting C–H⋯π(N ₃ ) interactions in the solid state.

Seven mononuclear manganese(III) complexes having the general formula [Mn(L)(X)(Y)] [where H₂L represents the tetradentate N₂O₂ donor salen-type Schiff base, and X and Y are monodentate ligands, e.g. pseudohalide, DMSO, H₂O, etc.] have been prepared and characterized by single crystal X-ray diffraction studies. Manganese(III) in each complex shows a six-coordinate distorted octahedral geometry. The equatorial positions of manganese(III) are occupied by the respective deprotonated tetradentate ligands, whereas the axial positions are occupied by monodentate ligands. The use of ethylenediamine or its derivative to prepare the H₂salen-type Schiff bases essentially produces manganese(III) complexes containing more or less planar salen²⁻ moieties. Incorporation of one methylene spacer in the diamine moiety gives manganese(III) complexes containing salen²⁻ ligands, significantly distorted from planarity. This distortion has been be quantified by measuring the angle between the plane of the phenyl ring(s) of the ligand and the equatorial plane of the complex. The energy associated with the formation of supra-molecules via non-covalent interactions was also estimated by DFT calculation. Bader's theory of “atoms in molecules” has been used to analyze the π-stacking interactions observed in the solid state of these complexes.