Bis(pyridyl)-disulfonamides: structural comparison with their carboxamidic analogues and the effect of molecular geometry and supramolecular assembly on their photophysical properties

The presence of sulphur and carbon atoms, respectively, in the amidic functional group in sulphonamides and carboxamides resulted in differences in the molecular geometry and electronic effect associated with the compounds. Three new disulfonamides, N-1,N-3-di(pyridin-2-yl)benzene-1,3-disulfonamide (L1), N-1,N-3-di(pyridin-3-yl)benzene-1,3-disulfonamide (L2) and N-1,N-3-di(pyridin-4-yl)benzene-1,3-disulfonamide (L3), have been synthesized to analyse the structural features in order to obtain an understanding of the presence of hydrogen bond synthons in amidic functional groups in the presence of different atomic centres. Disulfonamides have been characterized by single crystal XRD and structural comparison with dicarboxamides made important revelations regarding the dependence of geometry and electronic factors on the formation of varied hydrogen bond synthons. Hirshfeld surface (HS) analysis has been performed on L1, L2, L2' and L3', where L2' and L3' are the carboxamidic analogues of L2 and L3, in order to determine the intermolecular interactions present in the crystal lattice. HS analysis is in good agreement with the single crystal XRD analysis of the hydrogen bonding interactions. Further the photophysical properties of the disulfonamides have been studied and rationalized in terms of their supramolecular assembly in the solid state. Among the three disulfonamide compounds, L1 and L3 have shown aggregation caused quenching (ACQ), while the interesting aggregation induced emission (AIE) phenomenon has been observed in L2.