Structural, electrochemical and spectroscopic characterization of a new [Cu 2L 2(μ-Cl) 2] 2[CuCl 4] 2 dimer complex

Abstract

The bis{(μ 2-chloro)[2-(imidazol-4-yl)ethyl][(1-methylimidazol-2-yl)methyl]amine}dicopper(II) bis[tetrachloro-cuprate (II)] complex [Cu 2(HISMIMA) 2Cl 2] 2(CuCl 4) 2 (HISMIMA:[(2-(imidazol-4-yl)ethyl)(1-methylimidazol-2-yl)methyl)amine]) was obtained by serendipity during the reaction of the mononuclear [Cu(HISMIMA)Cl 2] complex and gaseous nitric oxide in methanolic solution. The title complex unit cell has the composition: an anion complex {[Cu 2(HISMIMA) 2Cl 2][CuCl 4] 2} 2− ( 1) and a cation complex [Cu 2(HISMIMA) 2Cl 2] 2+ ( 2). Cation 2 displays a crystallographic centrosymmetric Cu 2Cl 2 core with each Cu II atom coordinated to the tripodal ligand in a square pyramidal geometry (Addison parameter τ=0.07). In 1, a distorted octahedral geometry is observed, in which the Cu II ions are coordinated in a way similar to that in 2 but with an additional interaction with the [CuCl 4] 2− ions. Cyclic voltammetric experiments reveal that the title complex does not dissociate in acetonitrile solution and has E 1/2=−0.24 V vs NHE (Δ E p=0.19 V, i pa/ i pc=0.75) for the Cu IICu II to Cu ICu I process at the Cu(μ-Cl) 2Cu core.