Benzenesulfonyl incorporated chalcones: Synthesis, structural and optical properties

Although the optical properties and applicability of chalcones as potential nonlinear optical(NLO) materials is well known, hybrids having both chalcone and sulfonamide portions are relatively scarce. In this sense, we are seeking to show if combining both into a double functionalized compound will still have similar or better NLO responses. For this, we have synthetized three sulfonamide-chalcone analogues by changing the substituent bonded to the sulfonamide ring (I = ethoxy; II = Cl and III = Br). These compounds were characterized by spectroscopic methods (NMR, IR and HRMS) and thermal methods (HSM and DSC/TGA). Their crystal structures were determined by Single Crystal X-ray Diffraction (SCXRD) and their molecular structures were compared. Crystallographic results showed that one compound crystallizes in a triclinic system whereas the others crystallize in a monoclinic crystal system. Moreover, their crystal packing is dominated by C–H⋯O interactions. In addition to this study and to first characterize these compounds, linear and nonlinear optical (NLO) properties were performed on all three compounds dissolved in dimethyl sulfoxide. One-photon and two-photon absorption (2PA) spectra and incoherent second harmonic generation were obtained by employing different spectroscopic techniques. The interesting results observed in the linear and NLO measurements showed that different groups bounded to the same main backbone did not significantly modify their optical properties, although they strongly affect their crystal structures. σ2PA spectra reveal that the first excited state is allowed by both 1PA and 2PA, which indicates asymmetry in the charge distribution along the π-conjugated molecule structure. NLO properties of compounds I-III agree with other chalcones previously studied, which indicates that adding the benzenesulfonyl group does not influence these properties. Considering the similar experimental values for different substituents, the results further motivate investigation on substituent-based optical properties for other sulfonamide-chalcone hybrids.