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  • Tuning the optical properties of 2-thienylpyridyl iridium complexes through carboranes and anions.

Tuning the optical properties of 2-thienylpyridyl iridium complexes through carboranes and anions.

Chemistry (Weinheim an der Bergstrasse, Germany) (2015-02-11)
Lin Zhu, Xiao Tang, Qi Yu, Wen Lv, Hong Yan, Qiang Zhao, Wei Huang
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.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
n-Butyllithium solution, 11.0 M in hexanes
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n-Butyllithium solution, 2.0 M in cyclohexane
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