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.