Oxidative quenching within photosensitizer-acceptor dyads based on bis(bidentate) phosphine-connected osmium(II) bipyridyl light absorbers and reactive metal sites.

For the first time oxidative quenching of OsPN chromophores by reactive Pt or Pd sites containing , , -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)(dppcb)MCl](SbF) (M = Pt, ; Pd, ). The appearance of this additional energy release is not detectable in [Os(bpy)(dppcbO)](PF) (), where dppcbO is , , -1,2-bis(diphenylphosphinoyl)-3,4-bis(diphenylphosphino)cyclobutane.

Surprising photochemical reactivity and visible light-driven energy transfer in heterodimetallic complexes.

The bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) has been used for the synthesis of a series of novel heterodimetallic complexes starting from [Ru(bpy)(2)(dppcb)]X(2) (1; X = PF(6), SbF(6)), so-called dyads, showing surprising photochemical reactivity. They consist of [Ru(bpy)(2)](2+)"antenna" sites absorbing light combined with reactive square-planar metal centres. Thus, irradiating [Ru(bpy)(2)(dppcb)MCl(2)]X(2) (M = Pt, 2; Pd, 3; X = PF(6), SbF(6)) dissolved in CH(3)CN with visible light, produces the unique heterodimetallic compounds [Ru(bpy)(CH(3)CN)(2)(dppcb)MCl(2)]X(2) (M = Pt, 7; Pd, 8; X = PF(6), SbF(6)).

Regio- and chemoselective oxidation of the bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane via cobalt(II) mediated dioxygen activation.

The bis(bidentate) phosphine cis,trans,cis-1,2,3,4-tetrakis(diphenylphosphino)cyclobutane (dppcb) has been regioselectively oxidized leading to novel, hemilabile ligands. [Co2Cl4(dppcb)] (1a) is transformed via cobalt(II) mediated dioxygen activation into [Co2Cl4(2,3-trans-dppcbO2)] (2a) in excellent yield, where 2,3-trans-dppcbO2 is cis,trans,cis-2,3-bis(diphenylphosphinoyl)-1,4-bis(diphenylphosphino)-cyclobutane. By contrast, the in situ presence of dioxygen during the synthesis of Co2Br4(dppcb)] (1b) produces both [Co2Br4(2,3-trans-dppcbO2)] (2b) and [Co2Br4(1,3-trans-dppcbO2)] (3), where 1,3-trans-dppcbO2 is cis,trans,cis-1,3-bis(diphenylphosphinoyl)-2,4-bis(diphenylphosphino)-cyclobutane.

A novel linkage-isomeric pair of dinuclear Pd(II) complexes bearing a bis-bidentate tetraphos ligand.

The tetraphosphane all trans tetrakis-(di(2-methoxyphenyl)phosphanyl)cyclobutane) (o-MeO-dppcb) has been employed to coordinate metal dichlorides (metal = Ni(II), Pd(II) and Pt(II)), stereoselectively yielding the dinuclear complexes [Ni(2)Cl(4)(micro-(kappaP(1):kappaP(2):kappaP(3):kappaP(4)-o-MeO-dppcb))] and [Pt(2)Cl(4)(micro-(kappaP(1),kappaP(2):kappaP(3),kappaP(4)-o-MeO-dppcb))], characterized by two six and two five-membered metallacycles, respectively. Conversely, the reaction with PdCl(2) led, under comparable synthetic conditions, to the formation of the linkage-isomeric pair [Pd(2)Cl(4)(micro-(kappaP(1),kappaP(2):kappaP(3),kappaP(4)-o-MeO-dppcb))] and [Pd(2)Cl(4)(micro-(kappaP(1):kappaP(2):kappaP(3):kappaP(4)-o-MeO-dppcb))] in a ca. 4 : 1 ratio.