The orientational-ordering transition in single crystals of selected C60 complexes with organic donors followed by infrared spectroscopy

Investigations of infrared spectra of single crystals of the complex of fullerene C60 with dianthracene (DAN) and C60 grown from CS2 solution (clathrate) versus temperature, between 4 and ca. 430 K, have been performed. A phase transition for the complex and the clathrate accompanied by a splitting of the F1u(4) band into at least two components was detected at temperatures higher than 260 K. The line splitting was attributed to C60 symmetry lowering as a result of suppression of its rotation. Phase transitions at 80, 160 and 305 K have been observed for DAN C60 (C6H6)3; the nature of the transitions has been suggested.