Ionic Charge-Transfer Liquid Crystals Formed by Alternating Supramolecular Copolymerization of Liquid π-Donors and TCNQ

Organic Donor-Acceptor Complexes As Potential Semiconducting Materials

In this review article, the synthesis, characterization and physico-chemical properties of the organic donor-acceptor complexes are highlighted and a special emphasis has been placed on developing them as semiconducting materials. The electron-rich molecules, i. e., donors have been broadly grouped in three categories, namely polycyclic aromatic hydrocarbons, nitrogen heterocycles and sulphur containing aromatic donors. The reactions of these classes of the donors with the acceptors, namely tetracyanoquinodimethane (TCNQ), tetracyanoethylene (TCNE), tetracyanobenzene (TCNB), benzoquinone, pyromellitic dianhydride and pyromellitic diimides, fullerenes, phenazine, benzothiadiazole, naphthalimide, DMAD, maleic anhydride, viologens and naphthalene diimide are described. The potential applications of the resulting DA complexes for physico-electronic purposes are also included. The theoretical investigation of many of these products with a view to rationalise their observed physico-chemical properties is also discussed.

Strategic Insertion of Heavy Atom to Tailor TADF OLED Material for the Development of Type I Photosensitizing Catalytic Red Emissive Assemblies

The work presented in the manuscript describes a simple strategy for transforming thermally activated delayed fluorescent organic light-emitting diodes (TADF OLEDs) compound 10-(dibenzo[a,c]phenazin-11-yl)-10H-phenoxazine (DPZ-PXZ) into type I photosensitizer 10-(dibenzo[a,c]phenazin-11-yl)-10H-phenothiazine (DPZ-PHZ) by strategically introducing sulfur atom in the photosensitizing core. The synthesized compound DPZ-PHZ exhibits aggregation-induced enhancement (AIE) and through-space charge transfer (TSCT) characteristics and generates red emissive assemblies in mixed aqueous media. The original compound DPZ-PXZ exhibits well-separated HOMO and LUMO levels and is reported to have highly efficient reverse intersystem crossing (RISC). In comparison, the incorporation of sulfur atom in the phenothiazine donor regulates the electronic communication between donor and acceptor units and promotes the intersystem crossing (ISC) in DPZ-PHZ molecules. Interestingly, compound DPZ-PHZ exhibits rapid activation of aerial oxygen for instant generation of superoxide radical anion. Backed by excellent type I photosensitizing activity, DPZ-PHZ assemblies have high catalytic potential for the synthesis of benzimidazoles, benzothiazoles and quinazolines derivatives under mild reaction conditions. The work presented in the manuscript provides an insight into the combination of heavy atom approach and TSCT for achieving adequate electronic communication between donor and acceptor units, balanced RISC/ISC, and stabilized-charge separated state for the development of efficient type I photosensitizing assemblies.