MODEL COMPOUNDS THAT MIMIC COUPLED BIMUCLEAR COPPER PROTEINS AND ENZYMES. COPPER(I) COMPLEXES OF N,N,N′,N′-TETRAKIS(2′-BENZOIMIDAZOLYL METHYL)-α,α′-(DIMETHYLENE AMINO)PYRIDINE

Abstract

A number of properties and reactions of a new kind of synthetic dicopper oxygen carrier [Cu₂(PTB)]X₂ (X = ClO₄ ⁻, BF₄ ⁻ and Cl⁻), where PTB is N,N,N′,N′-tetrakis (2′-benzoimidazolyl methyl)-α,α′-(dimethylene amino)pyridine, are similar to those of coupled binuclear copper proteins and enzymes to a significant extent. The carriers serve as an active site model to mimic hemocyanin and tyrosinase. [Cu₂ (PTB)]²⁺ reacts very easily with O₂ and dioxygen adducts have been isolated. Colourless solutions of [Cu₂(PTB)]²⁺ in dimethyl formamide (DMF) show a total absence of absorption in the near ultraviolet and visible region, but with oxygen give a blueish solution with characteristic, multiple absorptions at 320–390, 430 and 535 nm as well as fluorescence emission spectra (ex = 305 nm, em = 360–375, 410–420 nm). With addition of ascorbic acid, the solutions decolourize, the oxy-deoxy cycle can be repeated several times. ESR spectra of [Cu₂(PTB)O₂]²⁺ in frozen DMF solution show an axial spectrum around g = 2 (Δms = ± 1 transition) and g = 4.2 (Δms = ± 2 transition), which can be interpreted as arising from a pair of magnetically coupled Cu(II) ions.

Key Words:

• N,N,N′,N′-tetrakis(2′-benzoimidazolyl methyl)-α,α′-(dimethylene amino)pyridine
• binuclear copper