Directly coupled versus spectator linkers on diimine ptii acetylides—change the structure, keep the function

Modification of light‐harvesting units with anchoring groups for surface attachment often compromises light‐harnessing properties. Herein, a series of [donor–acceptor–anchor] platinum(II) diimine (bis‐)acetylides was developed in order to systematically compare the effect of conjugated versus electronically decoupled modes of attachment of protected anchoring groups on the photophysical properties of light‐harvesting units. The first examples of “decoupled” phosphonate diimine PtII complexes are reported, and their properties are compared and contrasted to those of carboxylate analogues studied by a diversity of methods. Ultrafast time‐resolved IR and transient absorption spectroscopy revealed that all complexes have a charge‐transfer (CT) lowest excited state with lifetimes between 2 and 14 ns. Vibrational signatures and dynamics of CT states were identified; the assignment of electronic states and their vibrational origin was aided by TDDFT calculations. Ultrafast energy redistribution accompanied by structural changes was directly captured in the CT states. A significant difference between the structures of the electronic ground and CT excited states, as well as differences in the structural reorganisation in the complexes bearing directly attached or electronically decoupled anchoring groups, was discovered. This work demonstrates that decoupling of the anchoring group from the light‐harvesting core by a saturated spacer is an easy approach to combine surface attachment with high reduction potential and ten times longer lifetime of the CT excited state of the light‐absorbing unit, and retain electron‐transfer photoreactivity essential for light‐harvesting applications.N/

Some alkynyl-ruthenium complexes containing di-imine and tertiary phosphine ligands

Article first published online: 5 MAY 2008Reactions between [RuCl2(PPh3)2(Bu 2tbpy)], (1), and terminal alkynes in the presence of Tl[PF6], followed by chromatography on alumina, have given the mono-alkynyl complexes [RuCl(C≡CR)(PPh3)2(Bu 2tbpy)] (R = Ph 2, C6H4NO 2-4 3, CO2Me 4, Fc 5, CPh2(OH) 6), of which the single-crystal XRD molecular structures of 3, 4 and 5 are reported. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.Michael I. Bruce, Benjamin C. Hall, Brian W. Skelton, and Allan H. Whit

Room-temperature phosphorescence and energy transfer in luminescent multinuclear platinum(II) complexes of branched alkynyls

A series of luminescent branched platinum(II) alkynyl complexes, [1,3,5-{RC≡C(PEt3)2PtC≡C-C6H 4C≡C}3C6H3] (R = C 6H5, C6H4OMe, C6H 4Me, C6H4CF3, C5H 4N, C6H4SAc, 1-napthyl (Np), 1-pyrenyl (Pyr), 1-anthryl-8-ethynyl (HC≡CAn)), [1,3-{PYrC≡C(PEt3) 2PtC≡CC6H4C≡C}2-5-{(iPr) 3SiC≡C}C6H3], and [1,3- {PyrC≡C(PEt3)2PtC≡CC6H 4C≡C}2-5-(HC≡C)-C6H3], was successfully synthesized by using the precursors [1,3,5-{Cl(PEt 3)2PtC≡CC6H4C≡C} 3C6H3] or [1,3-{Cl(PEt3) 2PtC≡CC6H4C≡C}2-5-{(iPr) 3SiC≡C}C6H3]. The X-ray crystal structures of [1,3,5-{MeOC6H4C≡C-(PEt 3)2PtC≡CC6H4C≡C} 3C6H3] and [1,8-{Cl(PEt3) 2PtC≡C}2An] have been determined. These complexes were found to show long-lived emission in both solution and solid-state phases at room temperature. The emission origin of the branched complexes [1,3,5-{RC≡C(PEt3)2PtC≡CC6H 4C≡C}3C6H3] with R = C 6H5, C6H4OMe, C6H 4Me, C6H4CF3, C5H 4N, and C6H4SAc was tentatively assigned to be derived from triplet states of predominantly intra-ligand (IL) character with some mixing of metal-to-ligand charge-transfer (MLCT) (dπ(Pt) →π*(C≡CR)) character, while the emission origin of the branched complexes with polyaromatic alkynyl ligands, [1,3,5-{RC≡C- (PEt3)2PtC≡CC6H4C≡C} 3C6H3] with R = Np, Pyr, or HC≡CAn, [1,3-{PyrC≡C-(PEt3)2PtC≡CC6H 4C≡C}2-5-{(iPr)3SiC≡ C}C 6H3], [1,3-{PyrC≡C(PEt3) 2PtC≡CC6H4C≡C}2-5- (HC≡C)C6H3], and [1,8-{Cl(PEt3) 2PtC≡C}2An], was tentatively assigned to be derived from the predominantly 3IL states of the respective polyaromatic alkynyl ligands, mixed with some 3MLCT (dπ(Pt)→π *(C≡C-R)) character. By incorporating different alkynyl ligands into the periphery of these branched complexes, one could readily tune the nature of the lowest energy emissive state and the direction of the excitation energy transfer. © 2005 Wiley-VCH Verlag GmbH & Co.link_to_subscribed_fulltex