Research Projects

Harvesting of triplet energy via either thermally activated delayed fluorescence (TADF) or room-temperature phosphorescence (RTP) from organic compounds has attracted great attention in organic light-emitting diodes (OLEDs), sensing, and bio-imaging. However, the realization of such emission characteristics in purely organic macrocyclic compounds is largely unexplored due to a) lack of effective combinations of macrocyclic structures and TADF or RTP properties, and b) difficulty in their design and synthesis. To this context, macrocycles with TADF/RTP properties could expand the application of TADF/RTP to supramolecular chemistry. Therefore, there is an urgent need for high energy-efficient macrocyclic-TADF and/or-RTP emitters. The aim of the project is to design organic multiple donor-acceptor based macrocyclic systems (D2A-M-D2A, where M = macrocycle) having a low energy gap between the lowest singlet (S1) and triplet (T1) states conducive to TADF and/or RTP for breakthrough applications in OLEDs, and sensing using supramolecular chemistry. We will synthesize various macrocycles having angular orientation of D and A parts. The incorporation of linkers (additional donors, D′) to the A part in an angular fashion (120°) to construct a macrocycle would lead to a powerful strategy for tuning TADF/RTP properties. These macrocycles will be synthesized by simple nucleophilic aromatic substitution reactions between a wide variety of electron donors (carbazole, benzophenone, diphenyl sulfone) and electron deficient acceptor (phthalonitrile). This design will give rise to rigid geometry with a low S1-T1 gap allowing harvesting of both singlet and triplet excitons at ambient conditions. The project will require numerous cutting-edge characterization techniques that will provide exceptional training for young researchers involved in the project. Detailed thermal analysis (TGA, DSC) of the molecules will provide insights into the thermal stability and phase transitions, whereas characterization of single crystals using X-ray crystallography will probe structural information. Cyclic voltammetry results will be combined with semi-empirical DFT and TD-DFT computations to characterize energy levels and bandgaps, as well as the conformational dynamics of the donor/linker groups. In-depth photophysical characterization will be performed using ultraviolet-visible and photoluminescence spectroscopies. These studies will further lead to understanding triplet energy harvesting via sensitizing chemicals, and constructing electroluminescence devices.