Highly efficient aggregation-induced emission and stimuli-responsive fluorochromism triggered by carborane-induced charge transfer state

Highly efficient and stimuli-responsive luminescent materials are desirable candidates in various applications. In this work a bis(naphthyl)phenyl-substituted o-carborane (1) was synthesized by a Suzuki cross-coupling reaction. The X-ray crystal structure analysis indicates multiple weak interactions (intermolecular C-H center dot center dot center dot pi, intramolecular C-H center dot center dot center dot H-B, and intermolecular B-H center dot center dot center dot pi hydrogen bonding interactions) are present which may explain the high solid state emission efficiency (0.99). Compound 1 exhibits multiple fluorochromism towards mechanical force, solvent vapor and temperature, which holds promise for further application studies. The emission mechanism is mainly the intramolecular charge transfer induced by the electron-withdrawing carborane as supported by the TD-DFT calculations.