title: Rodlike bimetallic ruthenium and osmium complexes bridged by phenylene spacers. Synthesis, electrochemistry, and photophysics.
abstract: In the search for light-addressable nanosized compounds we have synthesized 10 dinuclear homometallic trisbipyridyl complexes of linear structure with the general formula [M(bpy)3-BL-M(bpy)3]4+ [M = Ru(II) or Os(II); BL = polyphenylenes (2, 3, 4, or 5 units) or indenofluorene; bpy = 2,2'-bipyridine]. By using a "chemistry on the complex" approach, different sizes of rodlike systems have been obtained with a length of 19.8 and 32.5 A for the shortest and longest complex, respectively. For one of the ruthenium precursors, [Rubpy-ph2-Si(CH3)3][PF6]2, single crystals were obtained by recrystallization from methanol. Their photophysical and electrochemical properties are reported. All the compounds are luminescent both at room and low temperature with long excited-state lifetimes due to an extended delocalization. Nanosecond transient absorption showed that the lowest excited state involves the chelating unit attached to the bridging ligand. Electrochemical data indicated that the first reduction is at a slightly more positive potential than for the reference complexes [M(bpy)3]2+ (M = Ru, Os). This result confirms that the best acceptor is the bipyridine moiety connected to the conjugated spacers. The role of the tilt angle between the phenylene units, in the two series of complexes, for the ground and excited states is discussed.
authors.affiliation: Molecular Photonics Materials, University of Amsterdam, Nieuwe Achtergracht 166, 1018 WV Amsterdam, The Netherlands.
authors.forename: Steve
authors.initials: S
authors.lastname: Welter
authors.forename: Nunzio
authors.initials: N
authors.lastname: Salluce
authors.forename: Arianna
authors.initials: A
authors.lastname: Benetti
authors.forename: Nicolette
authors.initials: N
authors.lastname: Rot
authors.forename: Peter
authors.initials: P
authors.lastname: Belser
authors.forename: Prashant
authors.initials: P
authors.lastname: Sonar
authors.forename: Andrew C
authors.initials: AC
authors.lastname: Grimsdale
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen
authors.forename: Martin
authors.initials: M
authors.lastname: Lutz
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Spek
authors.forename: Luisa
authors.initials: L
authors.lastname: De Cola