文摘
We apply crystal engineering principles to prepare organic co-crystals and salts of sulfadiazine and pyridines. Pyridines are molecular building blocks utilized in crystal engineering that can disrupt the hydrogen bonded (amidine) N鈥揌路路路N (pyrimidine) dimer within the parent sulfa drug (SD) crystals, while providing access to both co-crystals and salts. We have synthesized four co-crystals and three salts of sulfadiazine involving N,N-dimethyl-4-aminopyridine, 4-aminopyridine, 4-picoline, 4,4鈥?bipyridine, (E)-1,2-bis(4-pyridyl)ethylene, 1,2-bis(4-pyridyl)acetylene, and 4-(pyridin-4-yl)piperazine. Single-crystal X-ray analyses reveal three hydrogen-bond motifs, namely, dyads, rings, and chains based involving either (amidine/aniline) N鈥揌路路路N (pyridine/pyrimidine), (pyridinium) +N鈥揌路路路N鈥撀?/sup>(amidide), (aniline/piperazine) N鈥揌路路路O2S (sulfoxide) interactions, or a combination thereof. The hydrogen-bond motifs are assigned as D11(2), R22(8), R22(20), C22(17), and C22(13) graph sets. An analysis of the Cambridge Structural Database (CSD) reveals that the S鈥揘 bond length is generally shorter in complexes based on an anionic SD, which is consistent with the sulfonamide possessing greater S鈺怤 character. From an analysis of SD-based structures involving our work and the CSD, we present a heretofore not discussed role of tautomers at the co-crystal鈥搒alt boundary. Specifically, the ability of tautomeric forms of SDs to display reconfigurable exteriors, and thereby act as chameleons, enables SDs to accommodate different co-formers by assuming different geometries and adopting different regions along the co-crystal鈥搒alt boundary.
