Bis-benzimidazolyl diamide copper (II) complexes: Synthesis, crystal structure and oxidation of substituted amino phenols

A new tetradentate ligand N,N′-Bis (1-butyl-benzimidazol-2-yl-methyl)-hexane-1,6-dicarboxamide (b-GBSA) has been utilized to synthesize mononuclear copper (II) complexes with inner sphere anionic ligands like NO3−, Br− and Cl−. Two of the complexes [Cu(L)NO3]NO3 (1) and [Cu(L)Br]Br (2) have been structurally characterized. The geometry of copper (II) in (1) is a distorted octahedral with NO3− anion acting as a bidentate ligand, while for (2) the geometry is found to be a near square pyramidal. The complexes carry out the oxidation of substituted amino phenols in the presence of molecular oxygen. The oxidation gets blocked at the dihydrophenoxazinone stage for 2-amino-5-methyl phenol, and to o-quinone for 2-amino-4-tertiary butyl phenol, quite like the enzyme phenoxazinone synthase.