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 1 H NMR. The propeller-like structure significantly reduces the quantum yield of fluorescence of the anthracene chromophore.