Ruthenium complexes as nitric oxide donors and scavengers. Synthesis and crystal and molecular structure for mer,trans-[RuIICl3(NO+)(N-4-ethylisonicotinate)2], and mer,trans-[RuIIICl3(N-CH3CN)(N-4-ethylisonicotinate)2] as obtained via UV-photochemical activation of {RuII(NO+)}3+-core parent complex in acetonitrile solution

The synthesis of mer,trans-[(RuCl3)-Cl-II(NO+)(EINT)(2)](EINT = N-4-ethylisonicotinate), 1, was achieved by carefully working under ultrapure nitrogen atmosphere, by mixing (RuCl3)-Cl-III(NO)center dot H2O and EINT (1:2 M ratio in anhydrous ethanol) under stirring and at reflux conditions. Single crystals of 1 suitable for X-ray diffraction XRD techniques were also obtained by slow evaporation of solvent under nitrogen from the mother alcoholic solution. The IR spectrum of the solid (KBr matrixes) showed the characteristic sharp and intense band (1866 cm(-1)) relevant to the N-O stretching vibration for the nitrosyl ligand (Ru-II-NO+ core). Then, on irradiating at 25 degrees C a solution of 1 in ultrapure acetonitrile (contained in quartz cuvette) under an UV source (250 throughout 366 nm) a color turning from pink to yellow occurred. After a prolonged irradiation (250 nm for at least 6 h) the cuvette (yellow solution) was stored in a dry nitrogen atmosphere and allowed to slowly concentrate via spontaneous solvent evaporation. The solution produced brown crystals as parallelepipeds, suitable for XRD data collection, that belong to the monoclinic system, C2/c space group, and the molecular structure (mer,trans-[(RuCl3)-Cl-II(N-NCCH3)(EINT)(2)], 2) consists of complex molecules that are mostly paired via stacking interactions that involve the pyridine moiety and through (ethyl)CH3 center dot center dot center dot Cl(Ru), (pyridine)CH center dot center dot center dot Cl(Ru) and (ethyl)CH3 center dot center dot center dot O(=C) hydrogen bond type interactions. The crystals of the parent nitrosyl complex belong to the orthorhombic Pccn space group and the complex molecule has three chlorido ligands in the equatorial positions and two EINT ligands in the axial positions. The nitrosyl ligand occupy two positions that are trans to each other and have half occupancy each.