Nitrosyl linkage photoisomerization in heteroleptic fluoride ruthenium complexes derived from labile nitrate precursors

Four complexes with trans-ON–Ru–F coordinate were synthesized from the corresponding nitrate precursors. The treatment of fac-[RuNO(NH3)2(NO3)3] with hydrofluoric acid results in the substitution of the labile nitrate ligands by H2O and F−, whereas the treatment of trans-(NO,NO3)-cis-(NH3,NH3)-[RuNO(NH3)2Py2(NO3)](NO3)2·H2O leads to additional pyridine ligand elimination. The structures of the four complexes were characterized by X-ray diffraction: trans(NO,F)-cis(NH3,NH3)-[RuNO(NH3)2(H2O)2F]SiF6 (I), trans(NO,F)-cis(NH3,NH3)-[RuNO(NH3)2Py(NO3)F]2SiF6·H2O (II), trans(NO,F)-cis(NH3,NH3)-[RuNO(NH3)2Py(H2O)F](ClO4)2 (III) and trans(NO,F)-cis(NH3,NH3)-[(RuNOPy(NH3)2F)2(μ-O2H3)](ClO4)3 (IV). Upon light irradiation, complexes I, II and III show reversible formation of metastable linkage isomers MS1 and MS2 with remarkable thermal stability of both isomers. Moreover, complexes I and III show the highest thermal stability of the MS2 isomers, which leads to a higher photogeneration temperature of MS1 via the GS → MS2 → MS1 mechanism. Such excellent properties of the resulting materials can be used in the design of molecular based data storage devices.