Synthesis and Electrochemical Studies of Novel Isothiocyanato Macrocyclic Mn(III) Complexes: Experimental and Theoretical Studies

Abstract

The coordination chemistry of macrocyclic complexes are of considerable interest because of their various applications in bioinorganic systems, catalysis and analytical practices. Herein, we synthesized Mn(III) macrocyclic complex, MnN4-complex, and its isothiocyanato derivative MnN5-complex. These complexes were characterized by elemental, FT-IR, UV-Vis and Mass spectroscopic techniques and also by magnetic susceptibility measurements. The results of UV-vis spectral studies suggested that the intense absorption band in the 520–570 nm range is due to the intermolecular charge transfer transition which is associated with Mn–NCS bond in MnN5-complex. The electrochemical investigation indicated the stabilization of unusual oxidation state and modification of electronic structure of Mn central atom through SCN− coordination at fifth position of MnN4-complex. Further, geometric optimization of two complexes was also carried out by DFT calculations using B3LYP/6-31G* basis set. It was suggested that axial coordination of Cl is in interior of N4 cavity whereas NCS is at exterior.