A novel hydrogen‐bonding N‐oxide–sulfonamide–nitro N—H...O synthon determining the architecture of benzenesulfonamide cocrystals.

The structures of novel cocrystals of 4‐nitropyridine N‐oxide with benzenesulfonamide derivatives, namely, 4‐nitrobenzenesulfonamide–4‐nitropyridine N‐oxide (1/1), C5H4N2O3·C6H6N2O4S, and 4‐chlorobenzenesulfonamide–4‐nitropyridine N‐oxide (1/1), C6H6ClNO2S·C5H4N2O3, are stabilized by N—H...O hydrogen bonds, with the sulfonamide group acting as a proton donor. The O atoms of the N‐oxide and nitro groups are acceptors in these interactions. The latter is a double acceptor of bifurcated hydrogen bonds. Previous studies on similar crystal structures indicated competition between these functional groups in the formation of hydrogen bonds, with the priority being for the N‐oxide group. In contrast, the present X‐ray studies indicate the existence of a hydrogen‐bonding synthon including N—H...O(N‐oxide) and N—H...O(nitro) bridges. We present here a more detailed analysis of the N‐oxide–sulfonamide–nitro N—H...O ternary complex with quantum theory computations and the Quantum Theory of Atoms in Molecules (QTAIM) approach. Both interactions are present in the crystals, but the O atom of the N‐oxide group is found to be a more effective proton acceptor in hydrogen bonds, with an interaction energy about twice that of the nitro‐group O atoms. [ABSTRACT FROM AUTHOR]