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

The napthyl/pyridine-pyrazole-derived complexes, [Mn(L¹)Cl₂] (1), [Co(L¹)Cl₂] (2), [Cu(µ-Cl)(Cl)(L)]₂ (3), [Cu₂(L)₂(N₃)₃(µ2-N₃)] (4), and [Co(L²)Cl₂] (5) (where L¹ = bis-(3,5-dimethyl-pyrazol-1-ylmethyl)-napthalen-1-ylmethyl-amine (L¹), L = 5-methyl-pyrazol-1-ylmethyl) -napthalen-1-ylmethyl-amine (L) and L² = 2-[2-(3,5-dimethyl-pyrazol-1-yl)-1-methyl-ethyl]-pyridine), exhibited phenoxazinone synthase activity in methanol in the range 5–54 h⁻¹. 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. [ABSTRACT FROM AUTHOR]