Mononuclear manganese(III) complexes of bidentate NO donor Schiff base ligands: synthesis, structural characterization, magnetic and catecholase studies

We have synthesized four mononuclear manganese(III) complexes (1-4) of four closely related bidentate NO donor Schiff-base ligands, out of which three (2-4) were structurally characterized. Crystal structure determination reveals that all these complexes are in octahedral geometries. Magnetic studies have been carried out on complexes 2, 3 and 4 in the temperature range 2-300 K under a magnetic field of 0.1 T which yielded negative ZFS parameters of -2.96, -3.51 and -3.72 cm(-1) respectively. The catecholase activities of complexes 1-4 have been investigated following the oxidation of 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylbenzoquinone (3,5-DTBQ) with molecular oxygen in DCM at 25 degrees C, which were found to follow the Michalis-Menton type relation giving the highest TON (K-cat) for the so far reported Mn(III) complexes.