Resonance Raman evidence for photogeneration of a class II mixed-valence excited state of a binuclear copper(I) complex in solution

✍ Scribed by Keith C. Gordon; John J. McGarvey

• Publisher: Elsevier Science
• Year: 1990
• Tongue: English
• Weight: 456 KB
• Volume: 173
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(90)87232-g

✦ Synopsis

Pulsed laser resonance Raman (RR) studies of mono-and bi-nuclear complexes of Cu (1) with the bridging ligand 2,3-di-(2pyridyl)quinoxaline (dpq) and triphenyl phosphine (Ph,P) are reported. Laser flash photolysis at 416 nm or 532 nm in CHCI3 solution ofthe mononuclear complex, [ (Ph,P),Cu(dpq)]' (1) produced a transient with a lifetime of 37?2 ns (2O"C), attributable to the lowest energy metal ligand (dpq) charge-transfer excited state of (1). Under simdar conditions in CH,CI, solution, the binuclear complex, [ (Ph,P),Cu(dpq)Cu(PPh,)212+ (2), resulted in a weak transient absorbance signal, convoluted with the laser pulse, indicative ofan excited state with a lifetime less than the pulsed duration (circa 8 ns 1. Pulsed RR spectra generated at 416 nm of the excited state of (1) exhibited features attributable to the dpq-' radical anion. The much shorter-lived excited state of the binuclear complex (2) exhibited a virtually identical RR spectrum suggesting that it is a class II mixed valence species, [ (Ph,P)2Cu'(dpqq')Cu"(PPh~)z]*+, in which the dpq ligand does not strongly couple the two metal sites.