title: Direct observation of reversible electronic energy transfer involving an iridium center.
abstract: A cyclometalated iridium complex is reported where the core complex comprises naphthylpyridine as the main ligand and the ancillary 2,2'-bipyridine ligand is attached to a pyrene unit by a short alkyl bridge. To obtain the complex with satisfactory purity, it was necessary to modify the standard synthesis (direct reaction of the ancillary ligand with the chloro-bridged iridium dimer) to a method harnessing an intermediate tetramethylheptanolate-based complex, which was subjected to acid-promoted removal of the ancillary ligand and subsequent complexation. The photophysical behavior of the bichromophoric complex and a model complex without the pendant pyrene were studied using steady-state and time-resolved spectroscopies. Reversible electronic energy transfer (REET) is demonstrated, uniquely with an emissive cyclometalated iridium center and an adjacent organic chromophore. After excited-state equilibration is established (5 ns) as a result of REET, extremely long luminescence lifetimes of up to 225 μs result, compared to 8.3 μs for the model complex, without diminishing the emission quantum yield. As a result, remarkably high oxygen sensitivity is observed in both solution and polymeric matrices.
authors.affiliation: Université Bordeaux/CNRS, ISM , 351 cours de la Libération, 33405 Talence Cedex, France.
authors.forename: Sergey A
authors.initials: SA
authors.lastname: Denisov
authors.forename: Yanouk
authors.initials: Y
authors.lastname: Cudré
authors.forename: Peter
authors.initials: P
authors.lastname: Verwilst
authors.forename: Gediminas
authors.initials: G
authors.lastname: Jonusauskas
authors.forename: Marta
authors.initials: M
authors.lastname: Marín-Suárez
authors.forename: Jorge Fernando
authors.initials: JF
authors.lastname: Fernández-Sánchez
authors.forename: Etienne
authors.initials: E
authors.lastname: Baranoff
authors.forename: Nathan D
authors.initials: ND
authors.lastname: McClenaghan