Theoretical Simulations of Thermochromic and Aggregation-induced Emission Behaviors of a Series of Red-light Anthracene-o-carborane Derivatives.

Quantum mechanics and molecular dynamics simulations were carried out on a series of anthracene- o -carborane derivatives ( ANT-H , ANT-Ph , ANT-Me and ANT-TMS ) with rare red-light emission in solid state. The simulation on the heating process of the crystals and further comparison of the molecular structures and excited-state properties before and after heating help us to disclose the thermochromic behavior, i.e., the red-shift emission is caused by the elongation of the C1-C2 bond in the carborane moiety after heating. Thus we believe that the molecular structure in crystal is severely affected by the heating. Molecular conformation transformation appears in ANT-H crystal with the increase of temperature. More specifically, the anthracene moiety changes from nearly parallel to the C1-C2 bond to nearly perpendicular, leading to the disappearance of the short-wavelength emission after heating. As for the aggregation-induced emission phenomenon, the structures and photophysical properties were comparatively investigated in both isolated state and crystal state, which suggests that the energy dissipation in crystal surroundings was greatly reduced through hindering structure relaxation from excited state to ground state. We expect that the discussion of the thermochromic behavior provides a new analysis perspective for the molecular design of o -carborane derivatives.