L-PROLINE 2,5-DIHYDROXYBENZOIC ACID (1 1) - A ZWITTERION CO-CRYSTAL/

The crystal structure of L-proline 2,5-dihydroxybenzoic acid (1/1) (as determined by single-crystal X-ray diffraction), a rare example of a hydrogen-bonded, zwitterion co-crystal with non-linear optical propert ies, is reported. The colourless crystals are orthorhombic with a = 5. 896(2), b = 11.486(1), c = 18.016(3) Angstrom, Z = 4, space group P2(1 )2(1)2(1). The complex hydrogen-bond network within the structure is d iscussed in detail, and the possibilities of using such a material as a model system for theoretical and experimental investigations of hydr ogen bonding are addressed.