SOLID-STATE PHASE-TRANSITIONS AND MOLECULAR-REORIENTATION IN ORTHO-CARBORANE AND PARA-CARBORANE - AN ISOMER EFFECT

The proton nuclear spin-lattice relaxation times at 30 MHz have been measured for ortho- and para-carborane between 170 and 310 K and between 210 and 320 K, respectively. Para-carborane undergoes solid-solid transitions at about 300 and 238 K while the ortho isomer shows only one transition at about 265 K. The details of the phase transitions are discussed and molecular reorientation in the isomers is compared. © 1980 American Institute of Physics.