Structural, electrochemical and spectroscopic characterization of a new [Cu2L2(m-Cl)2]2[CuCl4]2 dimer complex

The bis{(m2-chloro)[2-(imidazol-4-yl)ethyl][(1-methylimidazol-2-yl)methyl]amine}dicopper(II) bis[tetrachloro-cuprate (II)] complex [Cu2(HISMIMA)2Cl2]2(CuCl4)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)Cl2] complex and gaseous nitric oxide in methanolic solution. The title complex unit cell has the composition: an anion complex {[Cu2(HISMIMA)2Cl2][CuCl4]2}22 (1) and a cation complex [Cu2(HISMIMA)2Cl2]2þ (2). Cation 2 displays a crystallographic centrosymmetric Cu2Cl2 core with each CuII atom coordinated to the tripodal ligand in a square pyramidal geometry (Addison parameter t ¼ 0:07). In 1, a distorted octahedral geometry is observed, in which the CuII ions are coordinated in a way similar to that in 2 but with an additional interaction with the [CuCl4]22 ions. Cyclic voltammetric experiments reveal that the title complex does not dissociate in acetonitrile solution and has E1=2 ¼ 20:24 V vs NHE (DEp ¼ 0:19 V, ipa=ipc ¼ 0:75) for the CuIICuII to CuICuI process at the Cu(m-Cl)2Cu core. q 2004 Elsevier B.V. All rights reserved