In situ Growth Transition Towards Helical Crystals of Achiral Molecules

Abstract

The synthesis of chiral crystals such as helical crystals is important due to their chirality-dependent applications in various fields. Since chiral crystals of achiral molecules are getting more attention, it is important to establish synthetic strategies for helical crystals of achiral molecules. Quite surprisingly, there are numerous examples of helical crystals of achiral molecules, although they are mostly obtained without specific synthetic strategies. Herein, it is proposed that Eshelby twist can be applied to noncovalent molecular crystals by introducing screw dislocations and demonstrates a successful synthesis of helical tube crystals of achiral titanyl phthalocyanine by vapor-phase crystal growth. The dislocations form where interfaces are created via growth transition from wire growth to tube growth upon growth temperature change. The screw dislocation is confirmed by Burgers vector analysis using transmission electron microscopy. The screw dislocation induces crystal twisting along the growth direction to dissipate the strain applied around the dislocation. The diffraction peak broadening of the (200) and (002) planes confirms the nonuniform strain, i.e., twisting force. This work offers a new approach for the synthesis of helical crystals from achiral molecules.