New class of tridentate 3N ligands and copper(II) complexes: A model for type-2 copper site of phenoxazinone synthase.

• Bioinspired copper(II) complexes are reported as the model for type 2 copper site in phenoxazinone synthases. • They catalyze the conversion of the substrate 2-aminophenol into 2-aminophenoxazine-3-one using molecular oxygen in water. • Spectral, redox, and kinetic studies were performed in water to mimic accurate enzymatic reaction conditions. A new series of copper(II) complexes [Cu(L)Cl 2 ] 1 – 5 , where L is dimethyl-(2-{[(pyridin-2-ylmethyl)-amino]-methyl}-phenyl)-amine (L1); dimethyl-{2-[(2-pyridin-2-yl-ethylamino)-methyl]-phenyl}-amine (L2); 2-((3-(dimethylamino) propylamino)-methyl)- N,N -dimethylbenzenamine (L3); 2-((2-(dimethylamino) ethylamino) methyl)- N,N -dimethylbenzenamine (L4) and (2-{[(1 H -benzimidazole-2-ylmethyl)-amino]-methyl}-phenyl)-dimethylamine (L5) have been synthesized and characterized as the model for type 2 copper site in phenoxazinone synthases. The molecular structure of 1 exhibits nearly a perfect square pyramidal geometry (τ , 0.01). The complexes showed Cu(II)/Cu(I) redox potentials around −0.128 to −0.215 V in water. The electronic spectra of 1 – 5 exhibited d-d transitions around 620–643 nm in water. All the complexes exhibit almost similar electron paramagnetic resonance (EPR) parameter (g || , 2.21–2.27; A ||, 161–175 × 10−4 cm−1) corresponds to square-based geometry. The complexes have catalyzed the conversion of substrate 2-aminophenol into 2-aminophenoxazine-3-one using molecular oxygen. The formation was accomplished by appearance of a new absorption band at 433 nm with the reaction rate of 6.14–9.89 × 10−3 s−1 in water. [ABSTRACT FROM AUTHOR]