Organometallic Ruthenium Nitrosyl Obtained by C–H Bond Activation – Photoinduced Delivery of Nitric Oxide and NO‐Mediated Antiproliferation Activity Studies

Abstract

The azo dye methyl red, which has carboxylato and azo functional groups, was used as a ligand for the synthesis of the cyclometalated RuIII complex [Ru(L1)(PPh3)2Cl] (1, L1H2 = 2‐{[4‐(dimethylamino)phenyl]diazenyl}benzoic acid) through C–H bond activation. Complex 1 was treated with nitric oxide to afford the organometallic ruthenium nitrosyl complex [Ru(L2H)(PPh3)2(NO)Cl][ClO4] (1a, L2H = 2‐{[4‐(dimethylamino)‐3‐nitrophenyl]diazenyl}benzoic acid). The molecular structures of 1·CH3OH and 1a·CH3OH were determined by X‐ray crystallography. The diamagnetic complex 1a with S = 0 ground state was studied by 1H and 31P NMR spectroscopy. In the nitrosyl complex, the coordinated NO is photolabile under UV and visible light, and the liberated NO was trapped by reduced myoglobin. The NO, photoreleased under visible light, was utilized in antiproliferation activity studies on human (A549, HEK293T, and HeLa) and mouse (NIH3T3) cancer cell lines.