Mixed-ligand copper(II) complexes with positive redox potentials

✍ Scribed by Mariappan Murali; Mallayan Palaniandavar

• Publisher: Springer
• Year: 1996
• Tongue: English
• Weight: 639 KB
• Volume: 21
• Category: Article
• ISSN: 0340-4285
• DOI: 10.1007/bf00136544

✦ Synopsis

Mixed-ligand complexes formed by reaction of Cu(C104) 2 with 3-(2-pyridyl)-5,6-diphenyl-l,2,4-triazine (dppt) as primary ligand and 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen), 2,9-dimethyl-l,10-phenanthroline (drop), N,N-bis(pyrid-2-ylmethyl)amine (dipica), N,N-bis(benzimidazol-2-ylmethyl)amine (bba), 1,3-bis(2-benzimidazolyl)-2-thiapropane (bbms) and 1,5-bis(benzimidazolyl)-3-thiapentane (bbes) as the secondary ligands have been isolated. They are of the type [Cu(dppt)L] (C104)2. nH20 , where n = 0 or 2. All complexes exhibit only one ligand field band and their cryogenic solution e.p.r, spectra are axial, with ~max and 911 values diagnostic of a square-based geometry. The spectral and redox data are consistent with facial coordination of the tridentate ligands. All the complexes exhibit a positive redox potential (versus n.h.e.).

The weak ~-bonding of dppt, caused by the highly electron-withdrawing phenyl rings, the strong K-back bonding involving phen and drop, and interligand repulsions appear to be responsible for the relatively positive Cun/Cu I redox potentials.