Catalytic aspects of a copper(II) complex: biological oxidase to oxygenase activity

Abstract

Abstract: A coper(II) complex, [Cu(dpa) 2(OAc)](ClO 4) (1) [dpa =2 , 2 ′-dipyridylamine; OAc = acetate], has been synthesized and crystallographically characterized. X-ray structure analysis revealed that this mononuclear Cu(II) complex crystallizes as a rare class of hexa coordination geometry named bicapped square pyramidal geometry with P2 1/ c space group. This copper complex displays excellent catalytic efficiency, k cat/ K M(h - 1) = 6.17 × 10 5 towards the oxidative coupling of 2-aminophenol (2-AP) to aminophenoxazin-3-one. Further, upon stoichiometric addition of copper(II) complex to 3,5-DTBC in presence of molecular oxygen in ethanol medium, the copper complex affords predominantly extradiol cleavage products along with a small amount of benzoquinone and a trace amount of intradiol cleavage products at a rate, k obs= 1.09 × 10 - 3min - 1, which provide substantial evidence for the oxygen activation mechanism. This paper presents a novel addition of a copper(II) complex having the potential to mimic the active site of phenoxazinone synthase and catechol dioxygenase enzymes with significant catalytic efficiency. Graphical Abstract : SYNOPSIS The mononuclear copper complex having unusual hexa coordination geometry exhibits significant catalytic efficiency, k cat/ K M(h - 1) = 6.17 × 10 5 towards oxidation of 2-aminophenol which predominantly produced extradiol cleavage products at a rate, k obs= 1.09 × 10 - 3min - 1 upon addition of 3,5-DTBC in presence of molecular oxygen. [Figure not available: see fulltext.].