Biomimetic studies related to the azide-inhibited Cu,Zn superoxide dismutases

Azide binding to imidazolate-bridged dinuclear copper(ii) complexes of macr ocyclic (L') and macrobicyclic (L) ligands has been investigated by EPR, UV -visible spectrophotometry and kinetics. The EPR spectra show that an azido bridge replaces the imidazolate bridge in the macrobicyclic complex while the azide anion is bound to one copper and the imidazolate bridge is broken in the macrocyclic complex. The rate constant of azide binding is very low for the complexes without labile coordination and relatively large for tho se with labile coordination, whatever the macrocycle or macrobicycle struct ure of the ligand.