Raman spectroelectrochemical studies and crystal structure of a binuclear copper(I) complex with a bridging diimine ligand

Keith Gordon, A.H.R. AlObaidi, P.M. Jayaweera, John McGarvey, John Malone, Steven Bell

Research output: Contribution to journalArticlepeer-review

31 Citations (Scopus)

Abstract

Raman spectroelectrochemical and X-ray crystallographic studies have been made for the binuclear copper(I) complex, [(Ph(3)P)(2)Cu(dpq)Cu(PPh(3))(2)][BF4](2), where dpq is the bridging ligand 2,3-di(2-pyridyl)quinoxaline. The X-ray data show that the pyridine rings are twisted out of plane with respect to the quinoxaline ring which is itself non-planar. The UV/VIS spectra of the metal-to-ligand charge-transfer excited state and those of the electrochemically reduced complex are similar. The resonance-Raman spectrum of the latter species exhibits little change in the frequency of the pyridinylquinoxaline inter-ring C-C bond stretching mode, compared to the ground electronic state. This suggests minimum change in the inter-ring C-C bond order in the electrochemically or charge-transfer generated radical anion. Semiempirical molecular-orbital calculations on both the neutral dpq and radical anion show two near-degenerate lowest unoccupied orbitals in the neutral species. One is strongly bonding across the inter-ring C-C bond while the other is almost nun-bonding. The Raman data suggest that it is this latter orbital which is populated in the transient and electrochemical experiments.
Original languageEnglish
Pages (from-to)1591-1596
Number of pages6
JournalJOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
Volume1
Publication statusPublished - 1996

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