title: Oxidative quenching within photosensitizer-acceptor dyads based on bis(bidentate) phosphine-connected osmium(II) bipyridyl light absorbers and reactive metal sites.
abstract: For the first time oxidative quenching of OsP2N4chromophores by reactive PtIIor PdIIsites containingcis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) is directly observed despite the presence of a saturated cyclobutane backbone "bridge". This dramatic effect is measured as a sudden temperature-dependent onset of a reduction in phosphorescence lifetime in [Os(bpy)2(dppcb)MCl2](SbF6)2(M = Pt,1; Pd,2). The appearance of this additional energy release is not detectable in [Os(bpy)2(dppcbO2)](PF6)2(3), where dppcbO2iscis,trans,cis-1,2-bis(diphenylphosphinoyl)-3,4-bis(diphenylphosphino)cyclobutane. Obviously, the square-planar metal centers in1and2are responsible for this effect. In line with these observations, the emission quantum yields at room temperature for1and2are drastically reduced compared with3. Since this luminescence quenching implies strong intramolecular interaction between the OsIIexcited states and the acceptor sites and depends on the metal⋯metal distances, also the single crystal X-ray structures of1-3are given.
authors.affiliation: Institute of General, Inorganic and Theoretical Chemistry, University of Innsbruck, Innrain 52a, 6020 Innsbruck, Austria.
authors.forename: Sylvia
authors.initials: S
authors.lastname: Eller
authors.forename: Barbara
authors.initials: B
authors.lastname: Trettenbrein
authors.forename: Dennis
authors.initials: D
authors.lastname: Oberhuber
authors.forename: Christof
authors.initials: C
authors.lastname: Strabler
authors.forename: Rene
authors.initials: R
authors.lastname: Gutmann
authors.forename: Wytze E
authors.initials: WE
authors.lastname: van der Veer
authors.forename: Markus
authors.initials: M
authors.lastname: Ruetz
authors.forename: Holger
authors.initials: H
authors.lastname: Kopacka
authors.forename: Dagmar
authors.initials: D
authors.lastname: Obendorf
authors.forename: Peter
authors.initials: P
authors.lastname: Brüggeller
keywords: Bis(bidentate) phosphine; Electron transfer; Heterodimetallic OsII–PtII and OsII–PdII complexes; Molecular devices; Oxidative quenching