High-temperature Raman spectroscopy of L,L-diphenylalanine single-crystal

The crystal structure of L,L-diphenylalanine (C18H20N2O3⋅xH2O) is investigated by polarized Raman spectroscopy at temperatures from 303 to 443 K over the spectral range 35-3300 cm−1. This dipeptide crystallizes in a tubular arrangement filled by water molecules, maintained by helical π-π stacking (phenyl…phenyl) interactions and intermolecular hydrogen bonds. We investigate the rearrangement of the diphenylalanine backbone and the role of water molecules concerning the previously reported phase transition above 413 K. To further support our vibrational results, thermal analysis and DFT calculations are also presented.