Imidazolyl-Substituted Benzo- and Naphthodithiophenes as Precursors for the Synthesis of Transient Open-Shell Quinoids

The synthesis of three novel imidazolyl-substituted sulfur-containing heteroacenes is reported. These heteroacenes consisting of annelated benzo- and naphthothiophenes serve as precursors for the generation of open-shell quinoid heteroacenes by oxidation with alkaline ferric cyanide. Spectroscopic and computational experiments support the formation of reactive open-shell quinoids, which, however, quickly produce paramagnetic polymeric material.

Heteroacene-Based Polymer with Fast-Switching Visible-Near Infrared Electrochromic Behavior

The electrochromic properties and application of electronically conducting polymers (ECPs) (PTRPZ-EDOT) consisting of a 3,4-ethylenedioxythiophene (EDOT) and the heteroacene-based molecular scaffold, 6H-pyrrolo[3,2-b:4,5-b'] bis [1,4] benzothiazine (TRPZ), are reported. Known for its high electron mobility and conducting properties, the novel TRPZ scaffold was synthesized to possess two EDOT molecules termini affording TRPZ-EDOT. Electropolymerization of TRPZ-EDOT resulted in remarkable spectroscopic and conductive properties suitable for electrochromic device fabrication. Using atomic force microscopy (AFM), the average surface roughness and surface topography of PTRPZ-EDOT polymer thin films were determined. Spectroelectrochemical data showed that the polymer achieved switching times of 4.07 (coloration) and 0.47 s (bleaching) at 539 nm. The PTRPZ-EDOT film exhibits an optical contrast of 36-44% at 539 nm between its neutral and colored states, respectively. The NIR region from 1000 to 1700 nm shows the appearance of charge carrier bands with a 0-1 V potential range. An electrochromic device was successfully fabricated from PTRPZ-EDOT, showcasing the potential and applicability of the polymer material for advanced technologies such as smart windows, flexible electrochromic screens, and energy storage devices.

A Stable Hexaazaoctacene Cruciform σ-Dimer

Buchwald-Hartwig coupling of a triisopropylsilyl (TIPS)-ethynylated dibromo-N,N'-dihydrotetraazapentacene with 1,4-bis(TIPS-ethynyl)-2,3-diaminonaphthalene furnishes a dihydrohexaazaoctacene. Its oxidation with MnO₂ results in a 7,7'-bi(hexaazaoctacenyl). In addition to eight TIPS-ethynyl groups, the bioctacene motif protects the azaoctacene subunits. The biazaoctacenyl displays a τ_1/2 of > 5 d in dilute solution under ambient conditions. In the crystalline state it is persistent for > 10 months.

The hetero-Friedel-Crafts-Bradsher Cyclizations with Formation of Ring Carbon-Heteroatom (P, S) Bonds, Leading to Organic Functional Materials

The interest in functional materials possessing improved properties led to development of new methods of their synthesis, which allowed to obtain new molecular arrangements with carbon and heteroatom motifs. Two of the classical reactions of versatile use are the Friedel-Crafts and the Bradsher reactions, which in the new heteroatomic versions allow to replace ring carbon atoms by heteroatoms. In the present work, we review methods of synthesis of C-S and C-P bonds utilizing thia- and phospha-Friedel-Crafts-Bradsher cyclizations. Single examples of C-As and lack of C-Se bond formation, involving two of the closest neighbors of P and S in the periodic table, have also been noted. Applications of the obtained π-conjugated molecules, mainly as semiconducting materials, flame retardants, and resins hardeners, designed on the basis of five- and six-membered cyclic molecules containing ring phosphorus and sulfur atoms, are also included. This comprehensive review covers literature up to August 2020.

Selenophene-containing heterotriacenes by a C-Se coupling/cyclization reaction

A new novel family of tricyclic sulfur and/or selenium-containing heterotriacenes 2-4 with an increasing number of selenium (Se) atoms is presented. The heterotriacene derivatives were synthesized in multistep synthetic routes and the crucial cyclization steps to the stable and soluble fused systems were achieved by copper-catalyzed C-S and C-Se coupling/cyclization reactions. Structures and packing motifs in the solid state were elucidated by single crystal X-ray analysis and XRD powder measurements. Comparison of the optoelectronic properties provides interesting structure-property relationships and gives valuable insights into the role of heteroatoms within the series of the heterotriacenes. Electrooxidative polymerization led to the corresponding poly(heterotriacene)s P2-P4.

High-Efficiency Perovskite Solar Cells Employing a S,N-Heteropentacene-based D-A Hole-Transport Material

We developed a new donor-π-acceptor-type hole-transport material (HTMs) incorporating S,N-heteropentacene as π-spacer, triarylamine as donor, and dicyanovinylene as acceptor. In addition to appropriate frontier molecular orbital energies, the new HTM showed high photo absorptivity in the visible region. Without the use of p-dopants, solution-processed mixed perovskite devices using the HTM achieved power conversion efficiencies of up to 16.9% and high photocurrents of up to 22.2 mA cm(-2). These results demonstrate that heteroacene can be an excellent building block to prepare alternative HTMs for perovskite solar cells and hold promise for further advancement through fine-tuning the molecular structure.