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.