Rietveld refinement of the cocrystal 2,4-dihydroxybenzoic acid-N'-(propan-2-ylidene)nicotinohydrazide (1/1).

A further example of using a covalent-bond-forming reaction to alter supramolecular assembly by modification of hydrogen-bonding possibilities is presented. This concept was introduced by Lemmerer, Bernstein & Kahlenberg [CrystEngComm (2011), 13, 55-59]. The title structure, C(9)H(11)N(3)O·C(7)H(6)O(4), which consists of a reacted niazid molecule, viz. N'-(propan-2-ylidene)nicotinohydrazide, and 2,4-dihydroxybenzoic acid, was solved from powder diffraction data using simulated annealing. The results further demonstrate the relevance and utility of powder diffraction as an analytical tool in the study of cocrystals and their hydrogen-bond interactions.