Linkage and redox isomerism in ruthenium complexes of catecholate, semiquinone, and o-acylphenolate ligands derived from 1,2-dihydroxy-9,10-anthracenedione (alizarin) and related species: syntheses, characterizations, and photophysics

The complexes Ru(CO)2L2(AL-2H) (AL = alizarin; L = PPh3, PCyc3, PBu3, P(m-NaSO3C6H4)3), Ru(CO)(dppe)(PBu3)(AL-2H), and RuH(CO)L2(AL-H) (L = PPh3, PCyc3), and Ru(CO)2L2(AR-2H) (AR = anthrarobin; L = PBu3) were prepared by reactions of Ru3(CO)12, L, and AL, and the complexes RuH(CO)(PPh3)2(AL-H), RuH(CO)(PPh3)2(QN-H) (QN = quinizarin), and RuH(CO)(PPh3)2(LQN-H) (LQN = leucoquinizarin) are prepared by reactions of RuH2(CO)(PPh3)3 with AL or QN. The AL-2H and AR-2H ligands act as 1,2-catecholates, whereas the AL-H, QN-H, LQN-H ligands are 1,9-o-acylphenolate ligands. RuH(CO)(PPh3)2(AL-H) is characterized by X-ray crystallography. The electrochemistry of these complexes is examined, and the semiquinone complexes Ru(CO)2L2(AL-2H)]+ (L = PPh3, PCyc3, PBu3) and Ru(CO)(dppe)(PBu3)(AL-2H)]+ are generated by chemical oxidation and were characterized by EPR and IR spectroscopy. The photophysical properties are also reported.