title: Highly Efficient Triplet Photosensitizers: A Systematic Approach to the Application of Ir(III) Complexes containing Extended Phenanthrolines.
abstract: A series of Ir(III) complexes, based on 1,10-phenanthroline featuring aryl acetylene chromophores, were prepared and investigated as triplet photosensitizers. The complexes were synthesized by Sonogashira cross-coupling reactions using a "chemistry-on-the-complex" method. The absorption properties and luminescence lifetimes were successfully tuned by controlling the number and type of light-harvesting group. Intense UV/Vis absorption was observed for the Ir(III) complexes with two light-harvesting groups at the 3- and 8-positions of the phenanthroline. The asymmetric Ir(III) complex (with a triphenylamine (TPA) and a pyrene moiety attached) exhibited the longest lifetime. Red emission was observed for all the complexes in deaerated solutions at room temperature. Their emission at low temperature (77 K) and nanosecond time-resolved transient difference absorption spectra revealed the origin of their triplet excited states. The singlet-oxygen ((1) O2 ) sensitization and triplet-triplet annihilation (TTA)-based upconversion were explored. Highly efficient TTA upconversion (ΦUC =28.1 %) and (1) O2 sensitization (ΦΔ =97.0 %) were achieved for the asymmetric Ir(III) complex, which showed intense absorption in the visible region (λabs =482 nm, ϵ=50900 m(-1)  cm(-1) ) and had a long-lived triplet excited state (53.3 μs at RT).
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Yue
authors.initials: Y
authors.lastname: Lu
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Niamh
authors.initials: N
authors.lastname: McGoldrick
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Frances
authors.initials: F
authors.lastname: Murphy
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Brendan
authors.initials: B
authors.lastname: Twamley
authors.affiliation: State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, P. R. China.
authors.forename: Xiaoneng
authors.initials: X
authors.lastname: Cui
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Colm
authors.initials: C
authors.lastname: Delaney
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Gearóid M Ó
authors.initials: GM
authors.lastname: Máille
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland.
authors.forename: Junsi
authors.initials: J
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, 116024, P. R. China.
authors.forename: Jianzhang
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Department of Chemistry, Trinity College Dublin, Dublin 2, Ireland. smdraper@tcd.ie.
authors.forename: Sylvia M
authors.identifier: http://orcid.org/0000-0003-1323-7245
authors.initials: SM
authors.lastname: Draper
keywords: 1,10-phenanthroline; UV/Vis spectroscopy; iridium complexes; photosensitizer; triplet state