title: Photoswitchable luminescence of rhenium(i) tricarbonyl diimines.
abstract: The synthesis, characterization, and X-ray crystal structures of [Re(diimine)(CO)(3)(dpe)](PF(6)) (dpe = 1,2-di(4-pyridyl)ethylene) compounds are reported. The cis-dpe complexes exhibit yellow luminescence after UV excitation, whereas the trans-dpe counterparts are nonluminescent. The luminescence quantum yields of the cis-dpe complexes are strongly dependent on the identity of the diimine ligand. Irradiation (350 nm) of the trans-dpe complexes induces trans --> cis dpe-ligand isomerization with quantum yields on the order of 0.2, and this process leads to an on-switching of yellow luminescence. After long 350-nm irradiation times, a steady state composed of roughly 70% cis- and 30% trans-dpe complexes is reached. The reverse cis --> trans photoisomerization reaction is induced by irradiating the cis-dpe complexes at 250 nm, switching off the yellow luminescence. For 250-nm excitation, photodecomposition of the [Re(diimine)(CO)(3)(dpe)](+) complexes competes efficiently with photoisomerization.
authors.affiliation: Beckman Institute, California Institute of Technology, Pasadena, CA 91125, USA.
authors.forename: Oliver S
authors.initials: OS
authors.lastname: Wenger
authors.forename: Lawrence M
authors.initials: LM
authors.lastname: Henling
authors.forename: Michael W
authors.initials: MW
authors.lastname: Day
authors.forename: Jay R
authors.initials: JR
authors.lastname: Winkler
authors.forename: Harry B
authors.initials: HB
authors.lastname: Gray