Ligand-based charge-transfer luminescence in ionic cyclometalated iridium(III) complexes bearing a pyrene-functionalized bipyridine ligand: A joint theoretical and experimental study

Edwin C. Constable, Markus Neuburger, Pirmin Rösel, Gabriel E. Schneider, Jennifer A. Zampese, Catherine E. Housecroft, Filippo Monti, Nicola Armaroli, Rubén D. Costa, Enrique Ortí

Research output: Contribution to journalArticle

41 Citations (Scopus)

Abstract

Two new heteroleptic iridium(III) complexes [Ir(ppy)2(pyr 2bpy)][PF6] ([1a][PF6]) and [Ir(dfppy) 2(pyr2bpy)][PF6] ([2a][PF6]), where Hppy = 2-phenylpyridine, Hdfppy = 2-(3,5-difluorophenyl)pyridine, and pyr 2bpy = 5,5′-bis(pyren-1-yl)-2,2′-bipyridine, have been synthesized and fully characterized. The single-crystal structures of pyr 2bpy and the complexes 4{[1a][PF6]}·2CH 2Cl2·9H2O and [2a][PF 6]·0.25CH2Cl2·H2O have been determined. The effect of the pyrene substituents on the electronic properties is investigated through a comprehensive photophysical and theoretical study on the two complexes in comparison to reference complexes without substituents on the ancillary ligand ([1][PF6] and [2][PF 6]) and by making absorption and luminescence titrations of ligand pyr2bpy. Both theory and experiment show that the intense and broad band appearing in the 400-500 nm region of the absorption spectra of [1a][PF6] and [2a][PF6] is due to intramolecular charge-transfer (ICT) transitions from the pyrene substituents to the bipyridine ligand. [1a][PF6] and [2a][PF6] exhibit luminescence bands centered above 650 nm, attributed to a charge-transfer triplet state located on the pyr2bpy ligand, lying at lower energy than the strongly emitting Ir-ppy→bpy triplet states of the complexes lacking the pyrene fragments. Such luminescence, detected both at room temperature and 77 K, shows that the appendage of luminophoric moieties to luminescent Ir-based centers may further widen the emission tuneability of this exploited class of luminescent materials through purely electrostatic effects exerted on a properly designed N^N ancillary ligand.

Original languageEnglish
Pages (from-to)885-897
Number of pages13
JournalInorganic Chemistry
Volume52
Issue number2
DOIs
Publication statusPublished - 2013 Jan 18
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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