The structure and electrochemistry of imidazolebis(1-10 phenanthroline)copper(II) nitrate

Abstract

[Cu(phen) 2(imidazole)](NO 3) 2 crystallizes in the triclinic space group P1(No.2) with a=8.807(2), b=8.941(4), c=17.135(4) Å, α=100.95(2), β=90.95(1), γ=100.187(9)°, and Z=2. The structure consists of discrete [Cu(phen) 2(imidazole)] 2+ ions with a distorted square pyramidal geometry about the copper. One of the cis-phenanthroline ligands is asymmetrically coordinated to the axial (CuN phen=2.225(6) Å) and equatorial (CuN phen=2.050(5) Å) sites, while the second phenanthroline (CuN phen=2.027(5) Å and CuN phen=2.021(5) Å) and the imidazole (CuN im=1.980(6) Å), occupy the remaining equatorial sites. The reversible one electron reduction potential of [Cu(phen) 2(imidazole)] 2+, ( E 1/2=0.10 V) in methanol, is more negative than that observed for [Cu(phen) 2](NO 3) 2, ( E 1/2=0.16 V). The relationship between the structure of [Cu(phen) 2(imidazole)](NO 3) 2 and the corresponding dimer [Cu 2(phen) 4(imidazolate)](NO 3) 3 is discussed, and the electrochemistry is compared to the negative shift in redox potential which is observed when the nuclease [Cu(phen) 2] 2+ binds to CT DNA.