Glycinium semi-malonate and a glutaric acid-glycine cocrystal: new structures with short O-H...O hydrogen bonds.

Glycinium semi-malonate, C(2)H(6)NO(2)(+)·C(3)H(3)O(4)(-), (I), and glutaric acid-glycine (1/1), C(2)H(5)NO(2)·C(5)H(8)O(4), (II), are new examples of two-component crystal structures containing glycine and carboxylic acids. (II) is the first example of a glycine cocrystal which cannot be classified as a salt, as glutaric acid remains completely protonated. In the structure of (I), there are chains formed exclusively by glycinium cations, or exclusively by malonate anions, and these chains are linked with each other. Two types of very short O-H...O hydrogen bonds are present in the structure of (I), one linking glycinium cations with malonate anions, and the other linking malonate anions with each other. In contrast to (I), no direct linkages between molecules of the same type can be found in (II); all the hydrogen-bonded chains are heteromolecular, with molecules of neutral glutaric acid alternating with glycine zwitterions, linked by two types of short O-H...O hydrogen bonds.