Physicochemical properties of protoporphyrin IX by metal ions in acetonitrile-water mixture solution

Abstract

The UV-vis absorption spectrum of protoporphyrin IX shows a very sharp and strong absorption maximum peak at 398 nm in acetonitrile-water mixture solution (1:1 v/v). When divalent metal ions such as Cu2+, Zn2+, and Ca2+ ion were added to protoporphyrin IX, metal protoporphyrin IX complexes were thereby produced. Cu-protoporphyrin IX complexes have the largest formation constant (Kf) among them. The fluorescence intensity of protoporphyrin IX was diminished by the presence of Cu2+ , Zn2+ , Ca2+ , Mn2+ , and Ni2+ ions as quenchers. However, Mg2+ , Mn2+ , and Ni 2+ ions are hardly combined with protoporphyrin IX. Mg2+ ion does not take part in the fluorescence quenching process of protoporphyrin IX in acetonitrile-water mixture solution. According to the Stern-Volmer plots, fluorescence quenching by Cu2+ , Zn2+, and Ca2+ ions involves static quenching, which is due to complex formation. On the contrary, dynamic quenching has a large influence on the overall quenching process, when Mn2+ and Ni2+ ions were added to protoporphyrin IX in acetonitrile-water mixture solution.