title: Tuning the optical properties of 2-thienylpyridyl iridium complexes through carboranes and anions.
abstract: 2-Thienylpyridyl iridium(III) complexes containing an o-, m-, or p-carboranylvinyl-2,2'-bipyridine ligand and various counteranions (denoted o-PF6, m-BF4, m-PF6, m-SbF6, m-ClO4, m-OTf, m-NO3, m-BPh4, m-F, m-Cl, and p-PF6) were synthesized by using C-formyl carboranes as starting materials. The solid-state structures of o-PF6, m-PF6, m-ClO4, and m-BF4 showed that the cations form twisted cavities in which the anions are fixed by multiple hydrogen bonds. Anion-hydrogen interactions were investigated for nine m-carborane-based complexes with different counteranions. All carborane-based iridium(III) complexes show similar phosphorescence yields in solution but significantly different emission in the solid state. Anion-exchange titration and theoretical calculations revealed the relationships between structures and optical properties. The size of the anion and C-H⋅⋅⋅X anion-hydrogen bonds strongly influence the phosphorescence quantum yield in the solid state. In particular, the Ccar-H⋅⋅⋅X hydrogen bonds between the carboranyl unit and the anion play an important role in solid-state phosphorescence. Complex p-PF6 was successfully applied in phosphorescence-lifetime bioimaging owing to its low toxicity and near-infrared emission.
authors: State Key Laboratory of Coordination Chemistry, Nanjing University, Nanjing 210093 (P.R. China).
authors: Lin
authors: L
authors: Zhu
authors: Xiao
authors: X
authors: Tang
authors: Qi
authors: Q
authors: Yu
authors: Wen
authors: W
authors: Lv
authors: Hong
authors: H
authors: Yan
authors: Qiang
authors: Q
authors: Zhao
authors: Wei
authors: W
authors: Huang
keywords: carboranes; chelates; imaging agents; iridium; phosphorescence