Spectroscopic and electrochemical study of dinuclear and mononuclear copper complexes with the bidentate ligand of the 2,2-biquinoline series

摘要

The newly synthesized complex (2) of copper(I) chloride with di-n-hexyl 2,2-biquinoline-4,4'-dicarboxylate (L) was spectroscopically and electrochemically characterized. The X-ray diffraction study showed that the crystals of complex 2 consist of the dinuclear moieties [L2Cu~2~I(μ-Cl)2] containing Cu2(μ-Cl)2 clusters. Spectrophotometric studies and ESI-mass spec-trometric measurements showed that after the dissolution of complex 2 in acetonitrile (AN) and N-methyl-2-pyrrolidone (NMP), the solution contained not only the dinuclear complexes [L2Cu_2~I(μ-Cl)2] but also [L2Cu~I]Cl, [LCu~ICl(Sol)], and [Cu~I(Sol)] (Sol is the solvent). The electrochemical data also confirm the conclusion that bridged dinuclear chloride complex 2 dissociates both in NMP and AN to form the tetrahedral bis-biquinoline complex [L2Cu~I]Cl. In solutions of complex 2 in alcohols and N,N-dimethylformamide (DMF), only [L2Cu~I]Cl and [Cu~ICl(Sol)] are present. In EtOH, AN, and DMF, [Cu~ICl(Sol)] undergoes disproportionation to [Cu~(II)Cl(Sol)] and Cu~0.