Synthesis, structure and catalytic promiscuity of a napthyl-pyrazole Mn(II) complex and structure–activity relationships

Abstract

The napthyl/pyridine-pyrazole-derived complexes, [Mn(L1 )Cl2] (1), [Co(L1 )Cl2] (2), [Cu(m-Cl)(Cl)(L)]2 (3), [Cu2(L)2(N3)3(m2-N3)] (4), and [Co(L2 )Cl2] (5) (where L1 ¼ bis-(3,5-dimethyl-pyrazol-1-ylmethyl)- napthalen- 1-ylmethyl-amine (L1 ), L ¼ 5-methyl-pyrazol-1-ylmethyl) -napthalen-1-ylmethyl-amine (L) and L2 ¼ 2-[2-(3,5-dimethyl-pyrazol-1-yl)-1-methyl-ethyl]-pyridine), exhibited phenoxazinone synthase activity in methanol in the range 5–54 h1 . Binuclear copper(II) derivatives 3 and 4 show better catalytic activities than manganese(II) and cobalt(II) derivatives. The kinetic studies reveal that phenoxazinone chromophore is produced via a complex- substrate intermediate. Further, 3 and 4 show catecholase activity in methanol in the presence of oxygen. All the complexes showed potent antimicrobial activity against the tested strains of bacteria and fungi. Complex 1 was synthesized for the first time by mixing L1 and MnCl2 (1:1) and characterized by single-crystal X-ray crystallography, cyclic voltammetry, density functional theory, and thermogravimetry analysis. The present study suggests that napthyl/ pyridyl-anchored pyrazole metal complexes are interesting scaffolds for the development of novel model compounds for biochemical reaction and efficient antimicrobial agents.