title: Iridium Cyclometalates with Tethered o-Carboranes: Impact of Restricted Rotation of o-Carborane on Phosphorescence Efficiency.
abstract: Iridium(III) cyclometalates (1c and 2c) in which the two carborane units on the 4- or 5-positions of 2-phenylpyridine (ppy) ligands were tethered by an alkylene linker were prepared to investigate the effect of free rotation of o-carborane on phosphorescence efficiency. In comparison with the unlinked complex, tethering the o-carboranes to the 5-positions of ppy ligands (2c) enhanced phosphorescence efficiency by over 30-fold in polar medium (Φ(PL) = 0.37 vs 0.011 in THF), while restricting the rotation of o-carborane at the 4-positions (1c) negatively affected the phosphorescence efficiency. The different effects of restricted rotation of o-carborane on phosphorescence efficiency were likely a result of the different variations of the carboranyl C-C bond distances in the excited state.
authors.affiliation: †Department of Chemistry and EHSRC, University of Ulsan, Ulsan 680-749, Republic of Korea.
authors.forename: Young Hoon
authors.initials: YH
authors.lastname: Lee
authors.affiliation: †Department of Chemistry and EHSRC, University of Ulsan, Ulsan 680-749, Republic of Korea.
authors.forename: Jihyun
authors.initials: J
authors.lastname: Park
authors.affiliation: §Department of Chemistry, Chonnam National University, Gwangju 500-757, Republic of Korea.
authors.forename: Junseong
authors.initials: J
authors.lastname: Lee
authors.affiliation: ‡Department of Applied Chemistry, Hanyang University, Ansan 426-791, Republic of Korea.
authors.forename: Sang Uck
authors.initials: SU
authors.lastname: Lee
authors.affiliation: †Department of Chemistry and EHSRC, University of Ulsan, Ulsan 680-749, Republic of Korea.
authors.forename: Min Hyung
authors.initials: MH
authors.lastname: Lee