Cyclometalated and NNN Terpyridine Ruthenium Photocatalysts and Their Cytotoxic Activity.

The cyclometalated terpyridine complexes [Ru(η 2 -OAc)(NC-tpy)(PP)] (PP = dppb 1 , ( R , R )-Skewphos 4 , ( S , S )-Skewphos 5 ) are easily obtained from the acetate derivatives [Ru(η 2 -OAc) 2 (PP)] (PP = dppb, ( R , R )-Skewphos 2 , ( S , S )-Skewphos 3 ) and tpy in methanol by elimination of AcOH. The precursors 2 , 3 are prepared from [Ru(η 2 -OAc) 2 (PPh 3 ) 2 ] and Skewphos in cyclohexane. Conversely, the NNN complexes [Ru(η 1 -OAc)(NNN-tpy)(PP)]OAc (PP = ( R , R )-Skewphos 6 , ( S , S )-Skewphos 7 ) are synthesized in a one pot reaction from [Ru(η 2 -OAc) 2 (PPh 3 ) 2 ], PP and tpy in methanol. The neutral NC-tpy 1 , 4 , 5 and cationic NNN-tpy 6 , 7 complexes catalyze the transfer hydrogenation of acetophenone (S/C = 1000) in 2-propanol with NaO i Pr under light irradiation at 30 °C. Formation of ( S )-1-phenylethanol has been observed with 4 , 6 in a MeOH/ i PrOH mixture, whereas the R -enantiomer is obtained with 5 , 7 (50-52% ee ). The tpy complexes show cytotoxic activity against the anaplastic thyroid cancer 8505C and SW1736 cell lines (ED 50 = 0.31-8.53 µ M), with the cationic 7 displaying an ED 50 of 0.31 µ M, four times lower compared to the enantiomer 6 .