The compounds nitrosyl cis-[Ru(bpy)(phen)TU(NO)](PF6)3 (compound 1) and cis-[Ru(bpy)(phen)(4-N-Imd)(NO)](PF6)3 (compound 2) (bpy = 2,2’-bipyridine, phen = 1,10’-phenanthroline, TU = thiourea and 4-N-Imd = 4-nitroimidazole) were synthesized and characterized by UV-visible, infrared spectroscopies and electrochemical techniques. In the study of the reactivity it was possible to verify the nitric oxide labilization by square wave voltammetry and a photochemical upon blue light irradiation. This feature is very important for a potential application in phototherapy. Additionally, the antibacterial activity of the nitrosyl complexes was tested against gram-negative bacteria Pseudomonas aeruginosa. Thus, it has been observed that the complexes are capable of inhibiting the growth of such microorganisms.

One experimental strategy to prepare a nitrosyl metal complex is based on the acid-base conversion of NO2- into NO+. Here, we employed UV-vis absorption and FTIR spectroscopies to investigate the reaction of cis-[Ru(NO2)(bpy)2(imN)]PF6 with H3O+, which produced cis-[Ru(NO)(bpy)2(imN)](PF6)3 complex. Chromatographic studies were carried out and showed that immediately after nitrite complex was dissolved only one species was present with retention time(tR) of 6.81 minutes. Addition of H3O+ to nitrite complex led to the formation of one major peak with tR of 3.92 min supporting nitrosyl complex formation. The reaction of nitrosyl complex with cysteine was also monitored by HPLC and it showed clearly the formation and followed decrease of a peak at 3.38 minute with maximum absorption at 380 nm, consistent with an intermediate complex. Later, it was observed the appearance of a peak at 4.15 minute with absorption band at 470 nm. In contrast to the reaction with cysteine, methionine did not show the formation of any intermediate. The use of HPLC was an important tool to support mechanistic assumptions for nitrosyl reactions.