Selective Growth of a C-70 Crystal in a Mixed Solvent System: From Cube to Tube

Abstract

Cube- and tube-shaped C-70 crystals were obtained selectively by reprecipitation using a combination of mesitylene (good solvent) and isopropyl alcohol (poor solvent). Both crystals include mesitylene molecules in their lattices; the ratios of C-70 to mesitylene were 1:2 in C-70 cubes and 1:0.7 in C-70 tubes. The volume ratio of mesitylene to IPA is a key parameter for the selective growth of C-70 cubes and C-70 tubes, rather than the supersaturation ratio, which governs crystal morphology in many other cases. Thus, we propose that the absolute amount of mesitylene near C-70 molecules determines the crystallization pathways for forming the C-70 2(mesitylene) or C-70 0.7(mesitylene) phase, which finally result in C-70 cubes or C-70 tubes, respectively.