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

[Cu(phen)2(imidazole)](NO3)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Nphen=2.225(6) Å) and equatorial (CuNphen=2.050(5) Å) sites, while the second phenanthroline (CuNphen=2.027(5) Å and CuNphen=2.021(5) Å) and the imidazole (CuNim=1.980(6) Å), occupy the remaining equatorial sites. The reversible one electron reduction potential of [Cu(phen)2(imidazole)]2+, (E1/2=0.10 V) in methanol, is more negative than that observed for [Cu(phen)2](NO3)2, (E1/2=0.16 V). The relationship between the structure of [Cu(phen)2(imidazole)](NO3)2 and the corresponding dimer [Cu2(phen)4(imidazolate)](NO3)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.