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

Abstract

A coper(II) complex, $$\hbox {[Cu(dpa)}_{2}\hbox {(OAc)](ClO}_{4})$$ (1) [dpa = $$ 2,2^\prime $$ -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 $$P2_{1}/\hbox {c}$$ space group. This copper complex displays excellent catalytic efficiency, $$\hbox {k}_{\mathrm{cat}}/\hbox {K}_{\mathrm{M} }(\hbox {h}^{-1}) = 6.17\times 10^{5}$$ 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, $$\hbox {k}_{\mathrm{obs}}= 1.09\times 10^{-3}$$ $$\hbox {min}^{-1}$$ , 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. SYNOPSIS The mononuclear copper complex having unusual hexa coordination geometry exhibits significant catalytic efficiency, $$\hbox {k}_{\mathrm{cat}}/\hbox {K}_{\mathrm{M}}(\hbox {h}^{-1}) = 6.17\times 10^{5}$$ towards oxidation of 2-aminophenol which predominantly produced extradiol cleavage products at a rate, $$\hbox {k}_{\mathrm{obs}}= 1.09\times 10^{-3}$$ $$\hbox {min}^{-1}$$ upon addition of 3,5-DTBC in presence of molecular oxygen.