LUMINESCENT AND REDOX-ACTIVE RUTHENIUM(II) AND OSMIUM(II) COMPLEXES WITH A RIGID ALLENE-BRIDGED POLYPHOSPHINE

A series of monometallic and homo- and hetero-bimetallic Ru-II and Os- II complexes with the polyphosphines 1,1'-bis(diphenylphosphino)ethene (bppe) and 1,1',3,3'-tetrakis(diphenylphosphino)allene (tppa) have be en prepared and characterized by P-31-{H-1} NMR spectroscopy elemental analysis and fast atom bombardment mass spectral analysis. Their grou nd-state properties (including electrochemical behavior and electronic absorption) and excited-state properties (including luminescence, qua ntum yields and MLCT excited state lifetimes) are reported herein. All complexes exhibit room-temperature luminescence, with long-lived (MLC T)-M-3 excited slates observed for monometallic and homobimetallic Os- II complexes with both bppe and tppa ligands. In the heterobimetallic Ru-II-Os-II complex [Ru(bpy)(2)(mu-tppa)Os(bpy)(2)][PF6] (bpy = 2,2'-b ipyridine) the luminescence of the Ru(bpy)(2)-based unit is quenched b y the connected Os(bpy)(2)-based unit via energy transfer across the t ppa spacer containing the allene bridge. Two overlapping one-electron oxidations, corresponding to the two MII-based moieties (M = Ru or Os) bridged by the tppa spacer, are observed in the homobimetallic comple xes.