Copper(I)-1,1,1-tris(diphenylphosphinomethyl)ethane complexes with different coordination modes tuned by auxiliary ligands and their spectroscopic properties

Three mono-, bi-and tetranuclear copper(I) complexes, [Cu(phen)(triphos-O)]BF4 (1) (phen = 1,10-phenanthroline, triphos = 1,1,1-tris(diphenylphosphinomethyl) ethane), [Cu-2(bipy)(triphos)(2)](BF4)(2) (2) (bipy = 4,4'-bipyridine), and [Cu-4(MeOC boolean AND N boolean AND N)(4)(triphos)(2)(bipy)](BF4)(4) (3) (MeOC boolean AND N boolean AND N = 6-(4-methoxyphenyl)-2,2'-bipyridine), have been synthesized and characterized by NMR spectroscopy, electrospray ionization, and matrix-assisted laser desorption ionization time-of-flight mass spectrometries, elemental analysis, and X-ray crystal analysis. The crystal structure investigation revealed the copper ions of the complexes have pseudo-tetrahedral coordination geometry. The electronic absorption spectra of 1, 2, and 3 contain low-energy bands at 350-500 and 400-650 nm, which are assigned to d(Cu) -> pi*(phen or bipy) and a mixture of d(Cu) -> pi*(MeOC boolean AND N boolean AND N) and d(Cu) -> pi* (bipy) transitions, respectively. Complex 2 displays a strong, long-lived solid-state emission with a maximum at 555 nm and lifetime of 13.6 mu s at room temperature. Photoinduced electron-transfer properties of 2 and 3 involving nanosecond time-resolved absorption spectroscopy and electron spin resonance techniques were studied.