Synthesis, characterization and emission properties of quinolin-8-olato chelated ruthenium organometallics

The reaction of Ru(RL¹)(PPh₃)₂(CO)Cl,1, with quinolin-8-ol (HQ) has afforded complexes of the type [Ru(RL²)(PPh₃)₂(CO)(Q)],3, in excellent yield (RL¹ is C₆H₂O-2-CHNHC₆H₄R(p)-3-Me-5, RL² is C₆H₂OH-2-CHNC₆H₄R(p)-3-Me-5 and R is Me, OMe, Cl). In this process, quinolin-8-olato (Q) undergoes five-membered chelation, the iminium-phenolato function tautomerizing to the imine-phenol function. In dichloromethane solution,3 displays a quasireversible3 ⁺/3 couple near 0·50 V vs SCE (3 ⁺ is the ruthenium (III) analogue of3). Coulometrically generated solutions of3 ⁺ display a strong absorption near 395 nm associated with a shoulder near 475 nm and rhombic EPR spectra withg values near 2·55, 2·13, 1·89. Solutions of3 absorb near 415 nm and emit near 510 nm at 298 K and 585 nm at 77 K. The fluorescence is believed to originate from the³MLCT state