Face-to-face stacking in sulfonamide based bis-ethylene bridged heteroaromatic dimers

Four sulfonamide based bis-ethylene bridged heteroaromatic dimers were synthesized for analysis of their structural and conformational properties. Interestingly, all models showed intramolecular offset face-to-face stacking between the tosyl group and heteroaromatic system in their solid state conformations. H-1 NMR of the solutions revealed that the conformations were not far off from the solid state stacked geometry. However, gaseous state optimizations of different conformers divulged that the crystal structures were the lowest energy conformers.