Investigation of polar crystalline materials containing hydrochlorothiazide: electron density distribution and optical properties

The polar hydrochlorothiazide polymorph (I) (systematic name: 6-chloro-1,1-dioxo-3,4-dihydro-2H-1,2,4-benzothiadiazine-7-sulfonamide, C7H8ClN3O4S2) and, recently designed by us, the polar 2-aminopyridine hydrochlorothiazide water <1/1/1> (C7H8ClN3O4S2·C5H6N2·H2O), (II), have been investigated. The crystal structures of both materials were determined using the single-crystal X-ray diffraction technique. The intermolecular interactions in (I) and (II) were studied in detail via topological electron-density analysis. The obtained results showed hydrogen bonds with a character intermediate between closed-shell and shared-shell in both crystal structures. The most important hydrogen bonds in (I) are formed between sulfonamide groups, whereas in (II), water molecules play a crucial role as they interconnect 2-aminopyridine and hydrochlorothiazide molecules. Calculations of the optical properties revealed that both materials exhibit large linear birefringence, twice that of calcite. The theoretically predicted second harmonic generation efficiency is four times and five times larger than that of KH2PO4 for (I) and (II), respectively. The information gathered on intermolecular interactions and structure–property correlations was used to identify the best strategies for the future design of new functional materials of this kind.