Bis(pyrazol-1-yl)methane as non-chromophoric ancillary ligand for charged bis-cyclometalated iridium(III) complexes

Sheng Meng*, Il Jung, Jie Feng, Rosario Scopelliti, Davide Di Censo, Michael Grätzel, M. Khaja Nazeeruddin, Etienne Baranoff

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)


New charged cyclometalated iridium(III) complexes [Ir(ppy) 2(L)](PF 6) [ppy = 2-phenylpyridine; L = bis(pyrazol-1-yl)methane (for 1); L = bis(3,5-dimethylpyrazol-1-yl)methane (for 2)] were synthesized and their electrochemical and photophysical properties studied. These complexes with non-π-electron-conjugated ancillary chelates exhibit significantly blueshifted emission relative to those of commonly used derivatives with NN ancillary ligands such as bipyridine or phenanthroline. Both X-ray and theoretical analysis based on time-dependent density functional theory (TD-DFT) reveal that the binding of Ir to the bis(pyrazol-1-yl)methane ancillary ligand is much weaker than that to the phenylpyridine main ligand; the effect is enhanced in the excited state. As a result, the ancillary ligand does not participate in low-energy excitations and triplet emission, and the electronic transitions are concentrated on the main chromophoric ligands. The blueshift feature is attributed to emission originating from the main cyclometalated ligands, in contrast to emitters with the NN chromophoric ancillary ligand. In addition, complex 2 exhibits a one order of magnitude higher non-radiative decay rate than complex 1, which is attributed to the steric hindrance of the methyl groups that leads to a more loosely bound ancillary ligand.

Original languageEnglish
Pages (from-to)3209-3215
Number of pages7
JournalEuropean Journal of Inorganic Chemistry
Issue number19
Publication statusPublished - 1 Jul 2012


  • Density functional calculations
  • Iridium
  • Luminescence
  • Molecular modeling
  • Pyrazole

ASJC Scopus subject areas

  • Inorganic Chemistry


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