High pressure synthesis and thermal properties of C60 dimers

A dimeric form of C60 is selectively synthesized by squeezing organic molecular crystal (ET)2C60 at 5GPa and 200 °C. Characterizations by Raman, infrared, and chromatographical studies provide unambiguous evidences for the dimeric form connected by 2+2 cycloaddition. Differential scanning calorimetry analysis showed that the heat of formation for the dimeric C60 is the largest among several polymeric phases of C60.