Luminescence of Ruthenium Halide Complexes Containing a Hemilabile Phosphine Pyrenyl Ether Ligand

A series of Ru(II) complexes, tcc-RuX2(POC4Pyr-P,O)2 (X = Cl (3), Br (4), I (5)), containing the hemilabile phosphine
pyrenyl ether ligand 4-{2-(diphenylphosphino)phenoxy}butylpyrene (POC4Pyr (1)) are reported. The synthesis and
spectroscopic properties of both the ligand, POC4pyr (1), and ligand oxide, P(O)OC4pyr (2), and the solid-state
structure of 1 are reported. Complexes 3−5 react rapidly with CO to give complexes ttt-RuX2(CO)2(POC4pyr-P)2 (X
= Cl (6), Br (7), I (8)). No pyrene excimer emission is detected from 3−5; however, different intensities of excimer
emission are observed for 6−8. The intensity of excimer emission decreases through the series, with 6 showing
the most intense response. The emission is solely due to intramolecular pyrene excimers at low concentrations
(≤10-4 M). Comparison of the UV−vis and steady-state fluorescence spectra shows overlap between the low
energy d−d absorption of 7 and 8 with excimer emission (480 nm), suggesting nonradiative energy transfer may
be occurring. Once excess CO is removed, complexes 6−8 isomerize to cis-dicarbonyl complexes cct-RuX2(CO)2(POC4Pyr-P)2 (X = Cl (9), Br (10), I (11)). The intensity of excimer emission from 9−11 increases with respect to
the excimer emission observed for 6−8, with 9 showing a significant increase in excimer intensity.