Dibrominated bis[1]­benzothieno­[3,2-b;2′,3′-e]­[1,4]­thiazines (BBTT) are efficiently synthesized and applied in Suzuki and Buchwald–Hartwig cross-coupling reactions to give access to 3,9-disubstituted BBTT derivatives with extended π-conjugation and enhanced electronic properties. For instance, 3,9-di­(hetero)­aryl substituted BBTT derivatives surpass their parent congeners phenothiazines with lower oxidation potentials and pronounced yellow to orange-red fluorescence (Φf ≈ 30–45%). In addition, 3,9-bis­(di­(hetero)­arylamino substituted BBTT possess very high lying HOMO energy (E HOMO = −4.46 to −4.83 eV), a favorable property of hole transport molecules. A representative X-ray structure analysis reveals that the central BBTT core in these extended π-systems is essentially planarized. Upon protonation of a 3,9-bis­(di­(hetero)­arylamino) substituted BBTT, the absorption color shifts from yellow to deep blue with a concomitant loss of the emission. The optical properties of these novel BBTT derivatives can be plausibly rationalized by time-dependent density functional theory (TD­(DFT)) calculations and correlation between experimentally determined oxidation potentials and σp parameters as well as between photophysical data and the specific substituent parameter σp – by establishing electronic structure–property relationships.

4-Pyrazolyl-1,2,3-triazoles can be readily synthesized in a one-pot fashion and moderate yield by employing a consecutive four-component process consisting of a sequentially Pd-Cu-catalyzed alkynylation-cyclocondensation-desilylation-CuAAC process. Most distinctly, (triisopropylsilyl)butadiyne is employed as a four-carbon building block in this one-pot de novo formation of both heterocyclic moieties.

A synthetic approach to two regioisomeric πelectron extended [1,4]thiaborins annulated with two benzothiophene units has been developed. The central thiaborin rings of the boracycles obtained exhibit different electronic properties; this is reflected in their different aromatic characters, boron Lewis acidity and UV-vis spectroscopic behavior. Thiaborins were converted to boron dipyrromethene (BODIPY) complexes. Their emission spectra exhibit two distinct bands resulting from 1 LE and 1 CT transitions. Strong near-infrared phosphorescence in Zeonex thin films at 77 K indicates efficient intersystem crossing and the formation of triplet states. Separation of HOMO and LUMO orbitals between boracyclic and BODIPY moieties facilitates electron transfer to a 1 CT state followed by a transition to the 3 LE triplet state located on the ligand. These unique properties of spiro thiaborin-BODIPY complexes were explored for their application as singlet-oxygen photosensitizers. They show excellent photocatalytic performance with singlet oxygen quantum yields reaching 77 % and full conversion of the model organic substrate achieved after 1.5 h with only 0.05 % mol catalyst load.

This review summarizes syntheses of S,N-heteropentacenes, i.e. electron-rich sulfur and nitrogen-embedding pentacycles, and briefly highlights selected applications in molecular electronics. Depending on the anellation mode and the number of incorporated heteroatoms, electron density can be raised by increasing nitrogen incorporation and polarizability is manifested by the sulfur content. In comparison to triacene analogues, the conjugation pathways of S,N-heteropentacenes are increased and the favorable acene-typical crystallization behavior allows for diverse application in organic electronics. Furthermore, substitution patterns allow fine-tuning the electronic properties, extending the π-systems, and supplying structural elements for further application.1 Introduction2 Thiophene-Centered S,N-Heteropentacenes2.1 Dipyrrolo-Fused Thiophenes2.2 Diindolo-Fused Thiophenes3 Pyrrole-Centered S,N-Heteropentacenes3.1 Dithieno-Fused Pyrroles3.2 Bis[1]benzothieno-Fused Pyrrole4 Fused 1,4-Thiazines4.1 Dinaphtho-Fused 1,4-Thiazines4.2 Bis[1]benzothieno-Fused 1,4-Thiazines5 Conclusions and Outlook

Invited for the cover of this issue are Krzysztof Durka and co‐workers at Warsaw University of Technology, University of Warsaw, Silesian University of Technology and Heinrich‐Heine‐Universität. The image depicts the generation of singlet oxygen by the BODIPY photosensitizer. Read the full text of the article at 10.1002/chem.202300680.