Synthesis and Structural Characterization of Cu(I) and Ni(II) Complexes that Contain the Bis[2-(diphenylphosphino)phenyl]ether Ligand. Novel Emission Properties for the Cu(I) Species

The pseudotetrahedral complexes [Cu(NN)(DPEphos)]BF4, where DPEphos = bis[2-(diphenylphosphino)phenyl]ether and NN = 1,10-phenanthroline (1), 2,9-dimethyl-1,10-phenanthroline (2), 2,9-di-n-butylphenanthroline (3), or
two dimethylcyanamides (4), and NiCl2(DPEphos) (5) have been synthesized and structurally characterized by
X-ray crystallography and their solution properties examined by use of a combination of cyclic voltammetry, NMR
spectroscopy, and electronic absorption spectroscopy. Complexes 1−4 possess a reversible Cu(II)/Cu(I) couple at
potentials upward of +1.2 V versus Ag/AgCl. Compounds 1−3 exhibit extraordinary photophysical properties. In
room-temperature dichloromethane solution, the charge-transfer excited state of the dmp (dbp) derivative exhibits
an emission quantum yield of 0.15 (0.16) and an excited-state lifetime of 14.3 μs (16.1 μs). Coordinating solvents
quench the charge-transfer emission to a degree, but the photoexcited dmp complex 2 retains a lifetime of over
a microsecond in acetone, methanol, and acetonitrile.