Aggregation-Induced and Polymorphism-Dependent Thermally Activated Delayed Fluorescence (TADF) Characteristics of an Oligothiophene: Applications in Time-Dependent Live Cell Multicolour Imaging.

Typically, molecules with a twisted donor-acceptor (D-A) architecture have been exploited for constructing thermally activated delayed fluorescence (TADF) materials. Herein, we report the first example of a thiophene-based thermally activated delayed fluorescent molecule without a D-A architecture. Compound 1 (2,5-bis(2,2-di(thiophen-2-yl)vinyl)thiophene) is conformationally flexible and shows weak fluorescence in the solution state but displays bright TADFin both condensed and solid states. Compound 1 crystallized in two different polymorphs (1 a and 1 b). Interestingly, both polymorphs show distinctly different TADF features. The broad spectral features and the TADF characteristics of 1 have been explored for the time-dependent multicolor (green, yellow and red) imaging of living cells.