Coumarin-embedded [5]helicene derivatives: synthesis, X-ray analysis and photoconducting properties

Two novel coumarin-embedded π-extended [5]helicene derivatives (3a and 6a) have been strategically synthesized and characterized, and the structure of 3a was determined via single crystal X-ray analysis. Both of them exhibit green fluorescence in dichloromethane. In addition, molecule 3a can aggregate to form a large quantity of nanowires through the re-precipitation method. More importantly, the photoelectric conversion properties of 3a nanowire-C60 based films are much better than those of the thin film of bulk 3a-C60, indicating that the ordered nanostructures are a crucial factor for enhancing device performance.

One-Pot Synthesis of Pyreno[2,1-b]furan Molecules with Two-Photon Absorption Properties

The development of large π-conjugated polycyclic heteroaromatic materials is of immense interest, both in the academic as well as the industrial community. Herein, we present the efficient one-pot synthesis of novel pyreno[2,1-b]furan molecules from a newly designed intermediate, which display intense green emission (505-516 nm) in solution and a large red shift emission (625-640 nm) in the solid state, because of strong π-π stacking. More interestingly, the compounds exhibit novel two-photon absorption (TPA) properties, and the TPA cross-section (δ) value was increased to 533 GM by regulating the electronic effects of the substituents of the pyreno[2,1-b]furan molecules. This study not only offers a facile strategy for constructing new pyrene-fused luminescence materials with two-photon absorption properties but also provides a new chemical intermediate that opens up a new pathway to advanced materials.

Pentagon-Containing π-Expanded Systems: Synthesis and Photophysical Properties

We have designed and synthesized three novel twistacene-modified enlarged pentagon-containing π-systems (6 and 9) with mismatched structures. The introduction of electron-withdrawing cyclopenta rings in the parent skeleton effectively stabilizes the electron-rich arenes. Their optoelectronic properties were studied via ultraviolet-visible (UV-vis) absorption spectra, fluorescence spectra, cyclic voltammetry, and density functional theory (DFT) calculation. In addition, chemical oxidation of the as-prepared compounds with nitrosonium hexafluoroantimonate could form the corresponding cationic radicals.

Expanded benzofuran-decorated twistacene derivatives: synthesis, characterization and single-component white electroluminescence

Two novel phenanthro[9,10-b]benzofuran and pyreno[4,5-b]benzofuran modified twistacene derivatives, 9 and 10, have been successfully synthesized via Suzuki coupling and then characterized. The photophysical properties were examined and DFT calculations were carried out in a comparative manner, and both molecules emitted strong blue light in organic solvents and in the solid state. Impressively, fabricated electroluminescent devices based on these single emitters radiate pure white light.

O-Annulation to Polycyclic Aromatic Hydrocarbons: A Tale of Optoelectronic Properties from Five- to Seven-Membered Rings

We take advantage of the Pummerer oxidative annulation reaction to extend PAHs through the formation of an intramolecular C-O bond with a suitable phenol substituent. Depending on the peripheral topology of the PAH precursor (e.g., pyrene, boron-dipyrromethene, or perylene diimide) five-, six-, and seven-membered O-containing rings could be obtained. The effect of the O-annulations on the optoelectronic properties were studied by various methods with the pyrano-annulated pyrene and BODIPY derivatives depicting quantitative emission quantum yields.

Synthesis of benzofurans from the cyclodehydration of α-phenoxy ketones mediated by Eaton’s reagent

Cyclodehydration of α-phenoxy ketones promoted by Eaton’s reagent (phosphorus pentoxide–methanesulfonic acid) is used to prepare 3-substituted or 2,3-disubstituted benzofurans with moderate to excellent yields under mild conditions. The method provides a facile access to benzofurans from readily available starting materials such as phenols and α-bromo ketones. The reaction is highly efficient, which is attributed to the good reactivity and fluidity of Eaton’s reagent. The reaction can be applied to prepare naphthofurans, furanocoumarins, benzothiophenes, and benzopyrans.

Intramolecular Electrophilic Cyclization Approach to 6-Substituted Naphtho[2,1- b]benzofurans: Novel Dual-State Emissive Fluorophores with Blue Emission

A regiospecific synthesis of naphtho[2,1- b]benzofurans with a substituent at the C6 position was achieved via intramolecular 6-endo-dig electrophilic cyclization under acidic conditions to construct the central aromatic C ring. Screening of the synthesized compounds using a high-content imaging system enabled us to discover novel dual state emissive compounds 2{ 1,6}, 2{ 1,8}, and 2{ 4,3}, which are highly emissive with blue emission in their solid states as well as in solution states in most solvents. In addition, the compounds 2{ 4,3}, 2{ 4,12}, and 2{ 5,13} were found to be the most cell permeable in HeLa cells for live cell imaging with negligible phototoxicity.

Synthesis, Optoelectronic and Self-Assembly Properties of Diazadioxaacene Derivatives

Two novel diazadioxaacene derivatives (ADOP and ADOQ) have been successfully synthesized and characterized. Their single crystal analyses disclose that molecule ADOP forms a twisted topology configuration, whereas ADOQ adopts reclining-chair architecture. Both of them emit strong blue fluorescence in organic solvents. Moreover, they can self-assemble to form regular nanobelts and nanowires, respectively, via a simple surfactant-assisted method.

Tailoring Colors by O Annulation of Polycyclic Aromatic Hydrocarbons

The synthesis of O-doped polyaromatic hydro- carbons in which two polycyclic aromatic hydrocarbon sub units are bridged through one or two O atoms has been achieved. This includes high-yield ring-closure key steps that, depending on the reaction conditions, result in the formation of furanyl or pyranopyranyl linkages through intramolecular C-O bond formation. Comprehensive photophysical measurements in solution showed that these compounds have exceptionally high emission yields and tunable absorption properties throughout the UV/Vis spectral region. Electrochemical investigations showed that in all cases O annulation increases the electron-donor capabilities by raising the HOMO energy level, whereas the LUMO energy level is less affected. Moreover, third-order nonlinear optical (NLO) measurements on solutions or thin films containing the dyes showed very good values of the second hyperpolarizability. Importantly, poly(methyl methacrylate) films containing the pyranopyranyl derivatives exhibited weak linear absorption and NLO absorption compared to the nonlinearity and NLO refraction, respectively, and thus revealed them to be exceptional organic materials for photonic devices.

Benzotrifuran (BTFuran): a building block for π-conjugated systems

Reported here is the first synthesis, X-ray crystal structure, and derivatization of C_3h-symmetric benzotrifuran (BTFuran), oxygen analog of the widely exploited benzotrithiophene.

Synthesis, Crystal Analyses, Physical Properties, and Electroluminescent Behavior of Unsymmetrical Heterotwistacenes

Four novel unsymmetrical heteroacenes containing five-membered heterocycles (OPyN, TPyN, TPyC, TPyO) have been synthesized and characterized. The formed molecules exhibited twisted structures, determined by crystal analysis and showed blue/green fluorescence in dichloromethane and in thin film. Compounds OPyN and TPyN were selectively used as active ingredients, and the fabricated devices displayed promising electroluminescent performance.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Azaacenes as active elements for sensing and bio applications

Recent progress in the application of azaacenes in sensing and bio-fields has been summarized.