Solvent exchange as a synthetic handle for controlling molecular crystals

Abstract

Organic/molecular crystals have been widely applied in medicine, imaging, explosives, and optoelectronics, but there are very limited methods for controlling their size and shape at the micro- or nanoscale. Herein, we develop solvent exchange as a new synthetic handle for creating complex morphologies in molecular crystals. With mitigated driving force in solution phase, solvent loss or exchange in C60 plates does not lead to structural collapse, but leads to crystal transformation to mesh networks. C70 and tetrakis(4-bromophenyl)ethylene crystals show similar transformation upon solvent exchange. We study the co-solvents and uncover their competing roles in the destabilization of the crystal structure and the on-site crystallization towards rods. This unconventional role of co-solvent is of importance not only for understanding the pore formation and crumbling, but also a new step towards regulating the desolvation and recrystallization processes. Rational transformation of organic crystals would open a new synthetic route for designing complex structures and new properties.