Photophysical Effect of the Coordination of Water by Ruthenium(II) Bipyridyl Complexes Containing Hemilabile Phosphine−Ether Ligands

A substantial concentration-dependent red shift of the absorption and emission spectra (77 K) of [Ru(bpy)2(POMe-P,O)]2+ (1) (POMe = (2-methoxyphenyl)diphenylphosphine) is reported. NMR experiments show this shift to be
due to equilibration of 1 with an aquo complex (1b) (Keff = (6 ± 3) × 10-3) that forms upon displacement of the
coordinated ether in the hemilabile POMe ligand. The excited-state lifetimes of 1 and 1b at 77 K in solid 2:1
ethanol/acetone solution are τ = 2.13 ± 0.02 and 1.95 ± 0.02 μs, respectively. The preparation and X-ray crystal
structure of a related complex, [Ru(bpy)2(POiPr-P)(OH2)](PF6)2 (2b) (POiPr-P = (2-(2-propoxy)phenyl)diphenylphosphine), is also reported. In solution, this species exists as an equilibrium mixture of complexes that cannot be
readily separated. This species also has concentration-dependent absorption spectra in 2:1 ethanol/acetone solution,
with a significant red shift (20 nm) at lower concentrations.