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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

51 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

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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