Synthesis, Structures, and Photophysical Properties of Ruthenium(II) Quinolinolato Complexes

Reaction of RuII(PR3)3Cl2 with 2-methyl-8-quinolinolate (MeQ) in the presence of Et3N in MeOH produced the neutral carbonyl hydrido complexes RuII(MeQ)(PR3)2(CO)(H) (R = Ph (1), MeC6H4 (2), MeOC6H4 (3)). An analogous reaction occurs between RuII(PPh3)3Cl2 and MeQH in ethanol to give RuII(MeQ)(PPh3)2(CO)(CH3) (4). The carbonyl, hydride, and methyl ligands of these complexes are most likely derived from the decarbonylation of ROH. Reaction of RuII(PPh3)3(CO)(H)2 with 5-substituted quinolinolato ligands (XQ, X = H, Cl, Ph) produced the neutral complexes RuII(XQ)(PPh3)2(CO)(H) (XQ = Q (5), ClQ (6), PhQ (7)). Treatment of 1 and 5–7 with excess KCN in MeOH following by metathesis with PPh4Cl afforded PPh4+ salts of the anionic carbonyl dicyano complexes RuII(XQ)(CO)(CN)2(PPh3)− (XQ = MeQ (8), Q (9) ClQ (10), PhQ (11)). Under similar conditions, reaction of 1 with excess CyNC in the presence of NH4PF6 afforded RuII(MeQ)(CyNC)2(CO)(PPh3)+ (12). All complexes have been characterized by IR, ESI/MS, 1H NMR and elemental analysis. The crystal structures of complexes 3, 4, 8, and 12 have been determined by X-ray crystallography. The UV and emission spectra of these complexes have also been investigated. All complexes exhibit short-lived quinolinolate-based LC fluorescence in solution at room temperature and dual emissions derived from LC fluorescence and phosphorescence at 77 K glassy medium. These emissions are relatively insensitive to the nature of the ancillary ligands but are readily tunable by varying the substituents on the quinolinolato ligand.