Synthesis, structures, photophysical properties, and dynamic stereochemistry of tri-9-anthrylsilane derivatives

A series of tri-9-anthrylsilanes having various substituents, such as -F, -H, -OH, -OMe, vinyl, and ethynyl, have been prepared, and their UV-vis absorption and fluorescence spectra have been determined. Chiral propeller-like arrangements of three anthryl groups have been confirmed by X-ray structural analysis of the fluoro and vinyl derivatives. In solution, however, all the trianthrylsilanes prepared herein undergo enantiomerization at room temperature. The free energies of enantiomerization are about 8-10 kcal mol(-1), determined by variable-temperature H-1 NMR. The propeller-like structure significantly reduces the quantum yield of fluorescence of the anthracene chromophore.