Colored optical waveguides in self-assembled thiadiazole-based materials

The photophysical features and waveguiding behavior of two series of thiadiazoles are reported. The different substitution patterns on the thiadiazole moiety (1,3,4- or 1,2,5-system) result in bent and linear molecular geometries in which the peripheral substitution plays a prominent role in their aggregation ability. Thus, only the presence of the 3,4,5-trimethoxyaryl moiety favors the aggregation of thiadiazoles 5 and 8 into crystalline supramolecular structures. The linear geometry and the aggregation of the methoxy-substituted benzo[c] [1,2,5] thiadiazole 8 have been corroborated by X-diffraction analysis. The photoluminescence (PL) quantum yields of the aggregated heterocycles 5 and 8 decreases with respect to the PL quantum yield in solution due to an aggregation-caused quenching (ACQ) effect. Despite this ACQ, the crystalline aggregates of both bent and linear thiadiazoles 5 and 8 exhibit waveguiding behavior with different emission colors (red, green and blue).