title: Ruthenium(II) 2,2'-Bipyridyl tetrakis acetonitrile undergoes selective axial photocleavage.
abstract: The complex [Ru(bpy)(AN)4]2+ (bpy = 2,2'-bipyridyl, AN = acetonitrile) has a Ru(II) --> pi(*)(bpy) MLCT band at 388 nm. Upon irradiation on this absorption band, the compound undergoes total regioselective photocleavage yielding complexes fac-[Ru(bpy)(AN)(3)(H(2)O)](2+) and trans-[Ru(bpy)(AN)(2)(H(2)O)(2)](2+) in two consecutive steps with quantum yields of 0.43 and 0.09, respectively. This behavior is a consequence of the stronger sigma-donor ability of the bpy nitrogens that determines the orbital ordering and therefore the nature of the lowest lying 3d-d state responsible for the photochemistry. The two-step photoreaction, which can be followed by UV-vis and NMR spectra, provides a quantitative path to the preparation of trans-polypyridine species with potentially interesting photochemical properties.
authors.affiliation: Departamento de Química InorgAnica, Analítica y Química Física, INQUIMAE, Facultad de Ciencias Exactas y Naturales Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, C1428EHA Buenos Aires, Argentina.
authors.forename: Agustín
authors.initials: A
authors.lastname: Petroni
authors.forename: Leonardo D
authors.initials: LD
authors.lastname: Slep
authors.forename: Roberto
authors.initials: R
authors.lastname: Etchenique