Crystallization of metastable β glycine from gas phase via the sublimation of α or γ form in vacuum

It is found that β glycine, the metastable polymorph of glycine, can be rapidly formed from gas phase via the sublimation of its stable α or γ form in vacuum. The transformation process was monitored by infrared spectroscopy and the crystal structure of the sublimate was identified by X-ray diffraction techniques. It is the first report about the transformation of stable α or γ glycine into metastable β form in “one-step” (heating then cool down spontaneously). Crystallization of β glycine from gas phase is very different from other methods that require additives in solution. The hydrogen-bonding interaction and self-assembling of amino acid were discussed based on the observations.