The bending behavior of an l-phenylalanine monohydrate soft crystal via reversible hydrogen bond rupture and remodeling

Abstract

The present study reports a novel L-phenylalanine monohydrate (L-Phe·H₂O) soft crystal, which has the potential to be developed as a medical microdevice owing to its flexibility and biosafety. Structure analysis indicated that there were plenty of directional hydrogen bonds distributed along almost every direction of the L-Phe·H₂O crystal, which appeared to be a rigid and brittle crystal. However, the L-Phe·H₂O crystal could be easily bent heavily and repeatedly. The aim of this study was to systematically investigate the bending mechanism of the L-Phe·H₂O soft crystal from the viewpoint of hydrogen bond variations. In situ micro-Raman and in situ micro-infrared spectra showed that the hydrogen bonds ruptured and rearranged during the bending process. According to the micro-X-ray diffraction results, the order of the L-Phe·H₂O lattice decreased in the bending region, and the varied lattice could return to its original state after straightening. Additionally, energy calculations suggested that the non-directional Coulomb attraction was the major force maintaining the macroscopic crystal integrity of L-Phe·H₂O when it was bent.