Exploitation of the electron deficient outer O4 compartment of a compartmental Schiff base to act as H-bond acceptors in forming a self-assembled dimer of a manganese(III) complex: A joint experimental and theoretical venture

Abstract

A mononuclear manganese(III) complex, [MnL1(DMSO)(OH2)]ClO4, where H2L1 = (2,2-dimethyl-(1,3-propylene))-bis(3-ethoxysalicylideneimine) is a tetradentate Schiff base ligand, has been synthesized and characterized by elemental and spectral analysis and single crystal X-ray diffraction. The most electron rich part of the cationic manganese(III) complex corresponds to the region where the four oxygen atoms (two from the ethoxy arms and two from the phenol groups) are located (−47 kcal/mol) and the most electron deficient part is located at the hydrogen atoms of the coordinated water molecule (+65 kcal/mol). This large value is due to the effect of the coordination of the oxygen atom to the manganese(III) center that increases the acidity of the water protons, thereby facilitating the formation of a H-bond mediated dimer. It is further stabilized by π⋯π stacking interactions involving the aromatic rings. The dimerization energy is very large confirming the relevance of this combination of interactions. The contribution of the H-bonds is also estimated, which confirms that the formation of the dimer is basically governed by the H-bonds.