Unprecedented strongly panchromic absorption from proton switchable iridium(III) azoimidazolate complexes

Adam Francis Henwood, Yue Hu, Muhammad Tariq Sajjad, Venkata Visveswara Gopala Krishna Thalluri, Sanjay Sanatan Ghosh, David Bradford Cordes, Alexandra Martha Zoya Slawin, Ifor David William Samuel, Neil Robertson, Eli Zysman-Colman

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Two novel heteroleptic iridium(III) complexes bearing an aryldiazoimidazole ligand are reported. These complexes differ structurally with respect to the protonation state of the imidazole ring, but can be independently accessed by varying the synthetic conditions. Their structures have been unequivocally confirmed by X-ray crystal structure analysis, with surprising differences in the structural parameters of the two complexes. The strongly absorbing nature of the free diazoimidazole ligand is enhanced in these iridium complexes, with the protonated cationic complex demonstrating extraordinarily strong panchromic absorption up to 700 nm. The absorption profile of the deprotonated neutral complex is blue-shifted by about 100 nm and thus the interconversion between the two complexes as a function of the acidity/basicity of the environment can be readily monitored by absorption spectroscopy. Theoretical calculations reveal the origins of these markedly different absorption properties. Finally, the protonated analogue has been targeted as an acceptor material for organic photovoltaic (OPV) applications and preliminary results are reported.
Original languageEnglish
Pages (from-to)19128-19135
Number of pages9
JournalChemistry - A European Journal
Issue number52
Early online date16 Nov 2015
Publication statusPublished - Dec 2015


  • Iridium
  • OPV
  • Dye
  • Panchromic diazo ligand


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