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. Copyright © 2012 American Chemical Society.