Manipulation of Molecular Aggregation States to Realize Polymorphism, AIE, MCL, and TADF in a Single Molecule

Abstract

Multifunctional emitting materials are scarce and need to be further explored. Now, a newly anthraquinone derivative, 2-(phenothiazine-10-yl)-anthraquinone (PTZ-AQ) was designed and synthesized and found to demonstrate polymorphism, multi-color emission, aggregation-induced emission (AIE), mechanochromic luminescence (MCL), and thermally activated delayed fluorescence (TADF) in its different solid forms. It is shown for the first time that TADF properties of a compound can be systematically tuned via its aggregation state. The optimized PTZ-AQ crystal shows a small singlet-triplet energy splitting of 0.01 eV and exhibits red TADF with a photoluminescence quantum yield as high as 0.848. This study shows that the unique multiple functions can be integrated into one single compound through controlling the aggregation states, which provides a new strategy for the investigation and application of multifunctional organic materials.

Thermally Activated Delayed Fluorescence Materials: Towards Realization of High Efficiency through Strategic Small Molecular Design

“…Lee et al. reported a rather intriguing molecule with AIE and TADF properties that also showed polymorphism and mechanochromic luminescence (MCL) phenomenon within the individual molecule . Five different aggregation states were found, including three different crystal structures.…”

Recent Advancements in and the Future of Organic Emitters: TADF‐ and RTP‐Active Multifunctional Organic Materials

“…More recently,L ee andc o-workers reported that as imilarD -Ac ompound, PTZ-AQ,w hich contained phenothiazine as a donor, showed multifunctional properties of AIDF,p olymorphism, andamechano-inducedl uminescence color change (Figure 29 a). [105] Depending on the crystallizationc onditions, PTZ-AQ could adopt up to fived ifferentp olymorphs with three different emission colors, yellow (l em = 545, 554 nm), orange (l em = 568 nm;O -crystal), and red (l em = 606,6 49 nm), and various F PL values within the range 0.02-0.84 (Figure29b). Amongt he different polymorphs, the R-crystal showed distinct TADF properties, with av ery small DE ST value (10 meV) and a high F PL value (0.84).…”

Thermally Activated Delayed Fluorescence: Beyond the Single Molecule

“…Implementing the techniques found in the works mentioned above to TADF systems becomes somewhat more complicated as there is now not just the behavior of the prompt singlet emission to explain but also the processes and energetics underlying rISC and delayed emission. Functional phenomena in TADF systems as a result of intermolecular interactions have been observed for a range of D-A and D-A-D systems (Hladka et al, 2018;Huang et al, 2018;Klimash et al, 2018;Pashazadeh et al, 2018;Shi et al, 2018;Skuodis et al, 2018;Bhatia and Ray, 2019;Zheng et al, 2019). These works provide methodologies and insights in understanding the influence that intermolecular interactions have on TADF emitters including their photophysical properties.…”