Raman study of molecular motions in organic charge-transfer complexes: Durene:TNB system

Molecular motions in the crystalline charge-transfer complex durene:sym-trinitrobenzene have been investigated using laser Raman spectroscopy. Isotopic substitutions of the donor and the acceptor are used to study relative amplitudes of various modes on the donor and the acceptor molecules. The low frequency motions comprised of phonons and intracharge-transfer modes appear to follow the giant molecule model with appreciable amplitude on both the donor and the acceptor molecules. The internal vibrations, on the other hand, can be characterized as totally a donor mode or an acceptor mode and show no observable exciton splittings. Splittings are found on the degenerate vibrations of the trinitrobenzene which suggest an appreciable distortion from D_3h symmetry of this molecules in the complex.