LOW-TEMPERATURE SYNCHROTRON-RADIATION STUDY OF A TWINNED DISORDERED CRYSTAL OF BIS(4,4'-BROMOPHENYL)-61,61-DIYL METHANO FULLERENE C-60

Synchrotron radiation diffraction measurements at 100 (5)K have been c arried out on bis(4,4'-bromophenyl)-61,61-diyl methano fullerene C-60 using area detector technology. In order to obtain a satisfactory desc ription of the data it is necessary to introduce both a twinning model of the crystal and a disorder model consisting of two different isome rs of the title compound. The study provides the first solid-state cha racterization of a 6-5 isomer of a methano fullerene. For the 6-6 isom er the geometry is in good agreement with recent literature on methane fullerenes. Unfortunately, the present study cannot resolve the bond lengths in the transannular region. The fact that the structure can be solved from diffraction data measured on a minute poorly scattering c rystal shows that the low-temperature single-crystal synchrotron radia tion technique is an indispensable tool in chemical crystallography.