New complexes of ruthenium nitrosyl with ethyl isonicotinate and pyrazine were prepared in the reaction of [RuNO(NO 2 ) 2 (H 2 O) 3 ] + with corresponding ligands. With the ligand excess the reaction results in cis-[RuNOL 2 (NO 2 ) 2 OH] with good yields (78% for I L = inicEt, 35% for II L = Pyz). The dimeric complex [(RuNO(Pyz)(NО 2 )(μ-NO 2 )) 2 μ-O] (III) forms in a small yield when less than 2 molar equivalents of pyrazine are taken for the reaction. Crystal structures of all three complexes were determined by single crystal XRD. Upon blue light irradiation complexes I and II undergo isomerization from Ru–NO (ground state, GS) to Ru-ON (metastable state, MS1) group. Reverse thermal transformation MS1 – GS was studied by IR and DSC techniques, activation parameters of MS1 – GS transition are: I - E a = 53.4(4.0) kJ mol −1 , lg k 0 = 10.6(4); II – E a = 58.9(4.3) kJ mol −1 , lg k 0 = 13.5(0.4).