Characterisation of a coordinated imidazole as a structural model for superoxide dismutase

The copper complex [Cu(HL)](ClO4)2·2H2O, where HL is N-[2-(4,7-dimethyl-1,4,7-triazacyclonon-1-yl)ethyl]–N-(benzimidazol-2-yl)methanimine, has been prepared and characterised by X-ray crystallography and solution absorption spectroscopy. Deprotonation of the benzimidazole moiety in this complex has been investigated by electronic spectroscopy. The results show a definite shift in λmax for [Cu(HL)]2+, at 632–818 nm for the deprotonated [CuL]+, in acetonitrile. This complex has been synthesised as a structural homologue to half of the enzyme Cu–Zn superoxide dismutase (SOD) which contains a bridged imidazolate moiety between the two Cu and Zn metal ions.