Photoinduced cytotoxic activity of a rare ruthenium nitrosyl phenanthroline complex showing NO generation in human cells

A new nitro-nitrosyl complex [RuNO(Phen)(NO 2 ) 2 OH] ( 1 ) was synthesized and characterized by X-ray diffraction, where Phen = 1,10-phenanthroline. The complex was crystallized in two different modifications without ( 1 ) and with a solvent molecule of DMF ( 1a ). The photolysis process together with the determination of the quantum yield of NO release was investigated in acetonitrile solution using a special flow-through system for the simultaneous registration of infrared (IR) and optical absorption (UV-vis) spectra under irradiation with 450 nm light. The quantum yield of photoinduced NO release was 4.0 ± 0.2%. DFT calculations showed that the main contribution to the absorption band at 450 nm is made by the HOMO/HOMO−1 → LUMO transitions, which are represented by the transfer of electron density from the -OH and -NO 2 ligands to the orbitals located on the Ru-NO bond. The dark and photoinduced cytotoxicity of the complex was studied against the human breast adenocarcinoma (MCF-7) and lung carcinoma (A549) cell lines and human non-tumor lung fibroblasts (MRC5). The complex shows a low cytotoxicity on MCF-7 cells (IC dark 50 = 90.6 ± 6.2 μM and IC irr. 50 = 95.3 ± 11.4 μM) and a moderate dark cytotoxicity on A549 and MRC5 cells (IC dark 50 = 33.4 ± 2.6 μM and IC dark 50 = 62.6 ± 3.1 μM, respectively), which slightly increases after irradiation (IC irr. 50 = 21.2 ± 3.3 μM and IC irr. 50 = 47.2 ± 2.3 μM, respectively). The article is devoted to the investigation of photochemical and biological properties of [RuNO(Phen)(NO 2 ) 2 OH] complex, such as crystal structure, quantum yield of photolysis reaction as well as cytotoxicity towards cell line MCF-7, A549 and MRC5.