C_70Ph_8 and C_70Ph_10: A computational and solid solution spectroscopic study

摘要

Mapping of the potential energy surface of the torsions of the phenyl groups of C_70Ph_8 and C_70Ph_10 by molecular mechanics reveals the existence of two conformers for each molecule. Energentically, both pairs are quasi-degenerate and therefore they could be experimentally detectable despite the low activation barriers for the inter-conversoin (2.4 kcal mol~(-1) for C_70Ph_8 and 3.9 kcal mol~(-1) for C_70Ph_10, respectively). In an effort to pin down the existence of the conformers, the laser induiced luminescence spectra of C_70Ph_8 and C_70Ph_10 were recorded in several solid solutions. The spectral features for C_70Ph_8 are rather independent of the nature of the environment and closely resemble those observed before in liquid solution with two main bands separated by more than 2000 cm~(-1). For C_70Ph_10, two new low-energy bands appear which were previously undetected in the liquid phase studies and which depend on the matrix. It is proposed that the doublet bands are fingerprints of the presence of the conformers.