Copper(I) complexes with N,O-donor Schiff base ligands related to intermediate forms of the TPQ cofactor in amine oxidases

Abstract

Neutral complexes (PPh3)2Cu(L) were obtained from (PPh3)2Cu(NO3) and the deprotonated forms of the three Schiff base ligands 2-(benzylideneimino)phenol (BimOH), 4-(benzylideneimino)resorcinol (Bim(OH)2) and N-(2,4-dihydroxy-5-isopropylphenyl)acetamide (DipaH3). The ligands were designed to model aminated intermediate forms of the topaquinone (TPQ) cofactor in the enzymatic cycle of copper-dependent amine oxidases. The ligands L are coordinated to the metal centers through imine-N and phenolate-O donor atoms to form five-membered chelate rings, in contrast to the six-membered chelate rings of salen-type Schiff base ligands. Compound (Bim(OH)O)Cu(PPh3)2·0.5CH3OH was structurally analyzed, it exhibits intramolecular aryl–aryl interactions between the ligands and intermolecular hydrogen bonds involving the free phenolic hydroxyl substituent, the coordinated phenolate oxygen atom and the methanol solvate molecule.