PHOTOPHYSICAL PROPERTIES OF RE(I) DIIMINE COMPLEXES - OBSERVATION OF ROOM-TEMPERATURE INTRALIGAND PHOSPHORESCENCE

The luminescence behavior of the ligands 4-styryl-4'-methyl-2,2'-bipyridine (mstyb) and 1,4-bis[2-(4'-methyl-2,2'-bipyridyl-4-yl)ethenyl]benzene (dstyb) and the Re(I) complexes [Re(CO)3(CH3CN)(mstyb)](PF6) and {[Re(CO)3(CH3CN)]2(dstyb)}(PF6)2 is discussed. The dstyb ligand exhibits intense fluorescence at room temperature and in frozen (4:1 ethanol-methanol) solutions. The ligand mstyb does not emit at room temperature, but shows both fluorescence and phosphorescence in frozen solutions in the presence of 10% ethyl iodide. The Re(I) complex of mstyb from a 3MLCT excited state (558 nm) in room-temperature acetonitrile; however, in frozen solutions structured phosphorescence from an intraligand 3(pi --> pi*) state (595 nm) is observed. The dinuclear Re(I) complex of dstyb exhibits structured intraligand phosphorescence (695 nm) in room-temperature solution and in low-temperature glasses. Gated emission spectra indicate that both intraligand phosphorescence and 3MLCT emission are observed from both complexes immediately following laser excitation at 77 K.