Tuning mesomorphic, spectral and nonlinear optical behavior in chalcogenophene triads: the role of oxygen, sulfur, and selenium.

Understanding structure-property relationships is essential for the rational design of new chemical compounds and functional materials. Here, we report the synthesis of nine new compounds incorporating oxygen (O), sulfur (S), or selenium (Se) as the chalcogen atom in the five-membered heterocycle central unit, together with a variable terminal chain. This systematic study investigates their mesomorphic properties, along with UV-Vis and fluorescence spectroscopy, as well as third-order nonlinear optical properties. Furan-based derivatives show exceptional spectral characteristics, emitting in the deep-blue region with high fluorescence quantum yields and strong third-order non-linear optical responses, despite limited mesomorphism. In contrast, thiophene- and selenophene-based compounds demonstrate a much stronger tendency to form mesophases, with their spectral and optical properties being significantly influenced by the nature of the heavy heteroatom. These findings underscore the critical role of heteroatom selection in modulating both molecular self-assembly and photophysical properties.