title: Energy transfer in hybrids based on a thiophene-substituted ethynylbipyridine dimer decorated with Re(I), Ru(II), and Os(II) units.
abstract: The preparation, structural features, electrochemical behavior, and optical properties (at room temperature and at 77 K) are reported for a series of thiophene-containing hybrids based on the bent conjugated backbone of a rigid ditopic ligand, the dimeric moiety 3,4-dibutyl-2,5-bis{5'-[(3,4-dibutylthien-2-ylethynyl)-2,2'-bipyridin-5-yl]ethynyl}thiophene (TBTBT). Within the dimer, the diethynyl-2,2'-bipyridine units (bpy, the coordination sites) alternate with three 3,4-dibuthylthiophene units and coordination of the [Re(CO)3Cl], [Ru(bpy)2]2+, and [Os(bpy)2]2+ centers results in the mononuclear species RuTBTBT and OsTBTBT and the binuclear species RuTBTBTRu, OsTBTBTOs, RuTBTBTOs, and ReTBTBTOs. At room temperature, the emitting states obtained by photoexcitation are of 3MLCT nature, and vibronic analysis of the emission spectra indicates that they are largely delocalized over the TBTBT ligand. In the binuclear species, the intermetal separation is ca. 17 A, and for RuTBTBTOs, an efficient Ru --> Os excitation transfer takes place, resulting solely in an Os-based emission. The process is ascribed to double-electron transfer (Dexter), as mediated by the TBTBT ligand; a similar conclusion holds for the case of ReTBTBTOs. For RuTBTBTOs, the process is discussed in some detail also with regard to the possibility of disentangling the constituent hole and electron-transfer events.
authors.affiliation: Istituto per la Sintesi Organica e la Fotoreattività, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy.
authors.forename: Sébastien
authors.initials: S
authors.lastname: Goeb
authors.forename: Antoinette
authors.initials: A
authors.lastname: De Nicola
authors.forename: Raymond
authors.initials: R
authors.lastname: Ziessel
authors.forename: Cristiana
authors.initials: C
authors.lastname: Sabatini
authors.forename: Andrea
authors.initials: A
authors.lastname: Barbieri
authors.forename: Francesco
authors.initials: F
authors.lastname: Barigelletti
mesh_terms: D004563:Electrochemistry; D004735:Energy Transfer; D008163:Luminescent Measurements; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D009992:Osmium / Q000737:chemistry*; D011725:Pyridines / Q000737:chemistry*; D012211:Rhenium / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013876:Thiophenes / Q000737:chemistry*
chemical_list: D009942:Organometallic Compounds; D011725:Pyridines; D013876:Thiophenes; D009992:Osmium; D012211:Rhenium; D012428:Ruthenium