High radiative efficiency based on intramolecular charge transfer in a 9,9'-bianthracene- ortho -carboranyl luminophore.

Herein, we prepared an o -carborane compound (9biAT) linked to a 9,9'-bianthracene moiety at each C9-position. The compound exhibited reddish emission in solid and solution states. The solvatochromism effect and theoretical calculation results for the excited (S ₁ ) state of 9biAT verified that the emission was attributed to ICT transition. In particular, the structural rigidity and the orthogonal geometry around the carborane enhanced ICT-based emission in the solution state at 298 K, resulting in a considerably high quantum efficiency ( Φ _em = 86%) in cyclohexane. In addition, both the Φ _em value and radiative decay constant ( k _r ) gradually decreased with an increase in the polarity of the organic solvent. Theoretical modelling of the charge distribution in the S ₁ -optimised geometry revealed that charge recombination in the radiative-relaxation process upon ICT transition could be delayed under polar conditions. Consequently, a high Φ _em value in the solution state at room temperature can be obtained by maintaining molecular rigidity and controlling the polarity of the environment.