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 quasireversible 3+/3 couple near 0,50 V vs SCE (3+ is the ruthenium (III) analogue of 3). Coulometrically generated solutions of 3+ display a strong absorption near 395 nm associated with a shoulder near 475 nm and rhombic EPR spectra with g values near 2,55, 2,13, 1,89. Solutions of 3 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 the 3MLCT state.