Material profiling for photocrystallography: Relating single-crystal photophysical and structural properties of luminescent bis- cyclometalated iridium-based complexes

J M Cole, K F Bowes, I P Clark, K S Low, Anita Zeidler, A W Parker, I R Laskar, T-M Chen

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Abstract

The photophysical properties of seven luminescent
iridium complexes are characterized in their single-crystal
form, and the photoactivity is related to their molecular
structures. Specifically, solid-state optical emission spectra and
associated lifetimes are determined from single crystals of
iridium complexes containing three bidentate ligands: two
variously substituted 2-phenylbenzothiazoles and either a 2,4-
pentadione (acetylacetone) or 2-pyridinecarboxylic (picolinic)
acid. All complexes studied exhibit emissive behavior in the
solid-state which originates from 3π−π* and metal-to-ligandcharge-
transfer (MLCT) electronic transitions; this is supported by density functional theory. Phosphorescence is observed in all
cases with microsecond lifetimes, ranging from 0.30 to 2.4 μs at 298 K and 1.4−4.0 μs at 100 K. Structure−property relationships
are established which are relevant to the potential solid-state application of this series of luminescent complexes as organic light
emitting diodes (OLED) material components. In addition, these materials are assessed for their suitability to time-resolved
pump−probe photocrystallography experiments, which will reveal their photoexcited state structure. Accordingly, the design
process by which materials are selected and technical parameters are defined for a photocrystallography experiment is illustrated.
This family of complexes presents a case study for this photocrystallography material profiling. Results show that the timeresolved
photoexcited state structure, featuring the MLCT transition is, in principle at least, viable for two of these complexes.
Original languageEnglish
Pages (from-to)1826-1837
JournalCrystal Growth and Design
Volume13
Issue number5
Early online date15 Mar 2013
DOIs
Publication statusPublished - 2013

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