“…However, for a co-crystal of glutaric acid with glycine such a transfer, though could be expected, was not observed -since a conformational polymorphic transition takes place at a much lower pressure than would be required for such a transfer [50]. As other examples of the systems for which the interplay between the structural transformations and solid-state acid-base (proton transfer) reactions at high pressure has been studied in relation to the paraelectric and ferroelectric properties, one can mention the co-crystals of phenazine with chloranilic, bromanilic, and fluoranilic acids [26], or of co-crystals of anilic acids and 2,3-Di(2-pyridinyl)pyrazine [27], where hydrogen bonds are polarized and neutral molecules are converted into ionized species on cooling down, or on increasing pressure.…”