title: Unprecedented Strong Panchromic Absorption from Proton-Switchable Iridium(III) Azoimidazolate Complexes.
abstract: Two new 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 blueshifted 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 revealed 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.
authors.affiliation: Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST (UK), Fax: (+44) 1334-463808 URL:http://www.zysman-colman.com.
authors.forename: Adam F
authors.initials: AF
authors.lastname: Henwood
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh, King's Buildings, Edinburgh EH93FJ (UK).
authors.forename: Yue
authors.initials: Y
authors.lastname: Hu
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife, KY16 9SS (UK).
authors.forename: Muhammad T
authors.initials: MT
authors.lastname: Sajjad
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife, KY16 9SS (UK).
authors.forename: Gopala K V V
authors.initials: GK
authors.lastname: Thalluri
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife, KY16 9SS (UK).|Current address: Optoelectronics Laboratory, Department of Physics, North Maharashtra University, Jalgaon-425001 (India).
authors.forename: Sanjay S
authors.initials: SS
authors.lastname: Ghosh
authors.affiliation: Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST (UK), Fax: (+44) 1334-463808 URL:http://www.zysman-colman.com.
authors.forename: David B
authors.initials: DB
authors.lastname: Cordes
authors.affiliation: Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST (UK), Fax: (+44) 1334-463808 URL:http://www.zysman-colman.com.
authors.forename: Alexandra M Z
authors.initials: AM
authors.lastname: Slawin
authors.affiliation: Organic Semiconductor Centre, SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews, Fife, KY16 9SS (UK).
authors.forename: Ifor D W
authors.initials: ID
authors.lastname: Samuel
authors.affiliation: EaStCHEM School of Chemistry, University of Edinburgh, King's Buildings, Edinburgh EH93FJ (UK).
authors.forename: Neil
authors.initials: N
authors.lastname: Robertson
authors.affiliation: Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St. Andrews, St. Andrews, Fife, KY16 9ST (UK), Fax: (+44) 1334-463808 URL:http://www.zysman-colman.com. eli.zysman-colman@st-andrews.ac.uk.
authors.forename: Eli
authors.initials: E
authors.lastname: Zysman-Colman
keywords: dyes; iridium; organic photovoltaic applications; panchromic diazo ligands