Oxygen bridged Homobinuclear Mn(II) compounds with Anthranilic acid: Theoretical calculations, oxidation and catalase activity

Abstract

Two new homobinuclear manganese compounds with mixed ligands, [Mn-2((1,1)-2-NH2C6H4COO)(2)(phen)(4)](ClO4)2(CH3OH) (1), and [Mn-2((1,3)-2-NH2C6H4COO)(2)(bipy)(4)](ClO4)2 (2) (NH2C6H4COOH=anthranilic acid, bipy=2,2-bipyridine, phen=1,10- phenanthroline) were synthesized and thoroughly characterized by elemental analysis, IR, UV and single crystal X-ray crystallography. X-ray structure analysis shows that in the mono- and bidentate carboxylate bridged compounds, Mn-Mn distances of 1 and 2 are 3,461 angstrom, and 4,639 angstrom, respectively. The energy of the compounds was determined with a DFT (Density Functional Theory) calculation on B3LYP/6-31G(d,p) optimized geometry by using the B3LYP/6-31G(d,p) basis set. These compounds acts as biomimetic catalyst and show catalase-like activity for the hydrogen peroxide dismutation at room temperature in different solvents with remarkable activity (TOF, Turnover frequency=mol of subst./(mol of cat. x time)) up to 12640h(-1) with 1, and 17910h(-1) with 2 in Tris-HCl buffer). Moreover, the catalytic activity of 1 and 2 has been studied for oxidation of alcohols (cinnamyl alcohol, benzyl alcohol, cyclohexanol, 1-octanol and 1-heptanol) and alkenes (cyclohexene, styrene, ethyl benzene, 1-octene and 1-hexene) in a homogeneous catalytic system consisting t-butylhydroperoxide (TBHP) as an oxidant in acetonitrile. Both compounds exhibited very high activity in the oxidation of cyclohexene to cyclohexanone (similar to 80% selectivity, similar to 99% conversion in 1h, TOF=243h(-1) and 226h(-1)) and cinnamyl alcohol to cinnamaldehyde (similar to 64% selectivity) as the main product with very high TOF value (9180h(-1) and 13040h(-1) in the first minute of reaction) (similar to 100% conversion in 0.5h) with TBHP at 70 degrees C in acetonitrile, for 1 and 2, respectively.