Geminal Cross-Coupling of 1,1-Dibromoolefins Facilitating Multiple Topological π-Conjugated Tetraarylethenes

Organic Bases as the Organic Electron Donors (OED) Promoted Reductive Coupling of Diarylhalomethanes: Halogens Controlled Construction of Tetraarylethylenes and Tetraarylethanes

Using the organic base as the organic electron donors, the reductive coupling of diaryhalomethanes was smoothly achieved under transition-metal-free reaction conditions, giving a series of synthetically important tetraarylethylenes and tetraarylethanes in high yields. The mechanistic study revealed that the organic bases acting as the electron donor initiated the generation of a radical intermediate, realizing the construction of tetraarylethylene and tetraarylethane skeletons.

Dimeric tetrabromo-p-quinodimethanes: synthesis and structural/electronic properties

Despite their great potential as molecular building blocks for organic synthesis, tetrabromo-p-quinodimethanes (TBQs) are a relatively unknown family of compounds. Herein, we showcase a series of five derivatives incorporating two tetrabromo-anthraquinodimethane (TBAQ) units linked by π-conjugated spacers of different nature and length. The resulting dimers TBQ1-5 are fully characterised by means of thorough spectroscopic measurements and theoretical calculations. Interestingly, owing to the steric hindrance imposed by the four bulky bromine atoms, the TBAQ fragments adopt a characteristically warped geometry, somehow resemblant of a butterfly, and the novel dimers show a complex NMR pattern with signal splittings. To ascertain whether dynamic processes regarding fluxional inversion of the butterfly configurations are involved, first-principles calculations assessing the interconversion energy barriers are performed. Three possible stereoisomers are predicted involving two diastereomers, thus accounting for the observed NMR spectra. The rotational freedom of the TBAQ units around the π-conjugated linker influences the structural and electronic properties of TBQ1-5 and modulates the electronic communication between the terminal TBAQ moieties. The role of the linker on the electronic properties is investigated by Raman and UV-vis spectroscopies, theoretical calculations and UV-vis measurements at low temperature. TBQ1-5 are of interest as less-explored structural building precursors for a variety of scientific areas. Finally, the sublimation, self-assembly and reactivity on Au(111) of TBQ3 is assessed.

Fluorescent cyclophanes and their applications

With the serendipitous discovery of crown ethers by Pedersen more than half a century ago and the subsequent introduction of host-guest chemistry and supramolecular chemistry by Cram and Lehn, respectively, followed by the design and synthesis of wholly synthetic cyclophanes-in particular, fluorescent cyclophanes, having rich structural characteristics and functions-have been the focus of considerable research activity during the past few decades. Cyclophanes with remarkable emissive properties have been investigated continuously over the years and employed in numerous applications across the field of science and technology. In this Review, we feature the recent developments in the chemistry of fluorescent cyclophanes, along with their design and synthesis. Their host-guest chemistry and applications related to their structure and properties are highlighted.

Cationic Conjugated Polyelectrolytes with Aggregation-Induced Ratiometric Fluorescence

The molecular diversity of aggregation-induced emission remains to be challenging due to the limitation of conventional synthesis methods. Here, a series of novel neutral and cationic conjugated polymers composed with various ratios of tetraarylethylene (TAE) containing a bridged oxygen (O) and fluorene (F) units are designed and synthesized via the geminal cross-coupling (GCC) of 1,1-dibromoolefins. The incorporation of TAE segments into the conjugated backbone of polyfluorene produces pronounced aggregation-induced ratiometric fluorescence (AIRF), i.e., aggregation-induced emission (AIE) at 520-600 nm grows synergistically with aggregations-caused quenching (ACQ) at 400-450 nm. The content of fluorene unit in the polymer backbones determines the intensity of the initial fluorescence at blue light region. The huge distinction (about 150 nm) in dual emission wavelengths caused by the environment change makes these conjugated polyelectrolytes particularly suitable for ratiometric fluorescence sensing. Based on electrostatic interaction mechanism, the gradual addition of heparin into the cationic conjugated polymers aqueous solutions could induce dual-color fluorescence changes with a detection limit of 9 nM. This work exhibits the great facility of using GCC reaction to synthesis the conjugated TAE polymers with superior AIE properties and special functions. This article is protected by copyright. All rights reserved.

Aggregation-Induced Emission Properties in Fully π-Conjugated Polymers, Dendrimers, and Oligomers

Aggregation-Induced Emission (AIE) in organic molecules has recently attracted the attention of the scientific community because of their potential applications in different fields. Compared to small molecules, little attention has been paid to polymers and oligomers that exhibit AIE, despite having excellent properties such as high emission efficiency in aggregate and solid states, signal amplification effect, good processability and the availability of multiple functionalization sites. In addition to these features, if the molecular structure is fully conjugated, intramolecular electronic interactions between the composing chromophores may appear, thus giving rise to a wealth of new photophysical properties. In this review, we focus on selected fully conjugated oligomers, dendrimers and polymers, and briefly summarize their synthetic routes, fluorescence properties and potential applications. An exhaustive comparison between spectroscopic results in solution and aggregates or in solid state has been collected in almost all examples, and an opinion on the future direction of the field is briefly stated.

Organic Semiconductors Processed from Synthesis-to-Device in Water

Organic semiconductors (OSCs) promise to deliver next-generation electronic and energy devices that are flexible, scalable and printable. Unfortunately, realizing this opportunity is hampered by increasing concerns about the use of volatile organic compounds (VOCs), particularly toxic halogenated solvents that are detrimental to the environment and human health. Here, a cradle-to-grave process is reported to achieve high performance p- and n-type OSC devices based on indacenodithiophene and diketopyrrolopyrrole semiconducting polymers that utilizes aqueous-processes, fewer steps, lower reaction temperatures, a significant reduction in VOCs (>99%) and avoids all halogenated solvents. The process involves an aqueous mini-emulsion polymerization that generates a surfactant-stabilized aqueous dispersion of OSC nanoparticles at sufficient concentration to permit direct aqueous processing into thin films for use in organic field-effect transistors. Promisingly, the performance of these devices is comparable to those prepared using conventional synthesis and processing procedures optimized for large amounts of VOCs and halogenated solvents. Ultimately, the holistic approach reported addresses the environmental issues and enables a viable guideline for the delivery of future OSC devices using only aqueous media for synthesis, purification and thin-film processing.

Dopant-Free Crossconjugated Hole-Transporting Polymers for Highly Efficient Perovskite Solar Cells

Currently, there are only very few dopant-free polymer hole-transporting materials (HTMs) that can enable perovskite solar cells (PVSCs) to demonstrate a high power conversion efficiency (PCE) of greater than 20%. To address this need, a simple and efficient way is developed to synthesize novel crossconjugated polymers as high performance dopant-free HTMs to endow PVSCs with a high PCE of 21.3%, which is among the highest values reported for single-junction inverted PVSCs. More importantly, rational understanding of the reasons why two isomeric polymer HTMs (PPE1 and PPE2) with almost identical photophysical properties, hole-transporting ability, and surface wettability deliver so distinctly different device performance under similar device fabrication conditions is manifested. PPE2 is found to improve the quality of perovskite films cast on top with larger grain sizes and more oriented crystallization. These results help unveil the new HTM design rules to influence the perovskite growth/crystallization for improving the performance of inverted PVSCs.

Tuning the fluorescence based on the combination of TICT and AIE emission of a tetraphenylethylene with D–π–A structure

A simple D–π–A structured tetraphenylethylene with two electron-rich methyloxy groups and two electron withdrawing cyano groups, which features both twisted intramolecular charge-transfer (TICT) and aggregation-induced emission (AIE) properties, namely TPEOMeCN has been prepared. The emission of TPEOMeCN examined in various solvents is dependent on the polarities of solvents, which indicates the TICT character. The emission intensity of the compound also enhances with the increasing water fraction in H₂O–DMSO mixtures, demonstrating the typical AIE property. Excitingly, the TICT and AIE emission could be observed separately or simultaneously by adjusting the water fraction or viscosity of the solvent. Encouragingly, the combined emission of the TPEOMeCN derived from this single molecule could be readily tuned via regulating the viscosity of the system, resulting in a broad emission peak which covers the visible spectrum (400–700 nm). This work provides a general strategy for designing molecules combining TICT emission and AIE for application as full-color emitters.

The combination of the TICT and AIE properties in a tetraphenylethylene based molecule with D–π–A structure is observed by simply adjusting the viscosity of the solvent.

Macrocycles and cages based on tetraphenylethylene with aggregation-induced emission effect

Syntheses, photophysical properties and applications of macrocycles and cages based on tetraphenylethylene with aggregation-induced emission (AIE) effect.

Geminal cross-coupling synthesis, ion-induced emission and lysosome imaging of cationic tetraarylethene oligoelectrolytes

Novel ratiometric AIE-active tetraarylethene oligoelectrolytes synthesized by geminal cross-coupling show ion-induced emission and are applied as bioprobes for lysosome tracing.

Functionalization of pentacene-5,7,12,14-tetraone with geminal enediyne and 1,3-dithiole groups

Pentacene-5,7,12,14-tetraone was subjected to selective olefination and cross-coupling reactions to yield a new class of pentacene-based π-conjugated systems with intriguing structural, electronic, and redox properties.

Polymerization of α-(halomethyl)acrylates through sequential nucleophilic attack of dithiols using a combination of addition–elimination and click reactions

Polycondensation involving sequential nucleophilic attacks of a dithiol on an α-(bromomethyl)acrylate efficiently yielded a polysulfide.

Monodisperse AIE-Active Conjugated Polymer Nanoparticles via Dispersion Polymerization Using Geminal Cross-Coupling of 1,1-Dibromoolefins

Monodisperse AIE (aggregation-induced emission)-active conjugated polymer nanoparticles are synthesized by dispersion polymerization using geminal Suzuki cross-coupling of 1,1-dibromoolefins. The size of the nanoparticles can be adjusted by varying the concentration of the initial monomer.

Facile synthesis and properties of dithieno[3,2-b:2′,3′-d]arsoles

The dithienoarsole skeleton can be safely and easily constructed, by a method superior to conventional synthetic routes. The obtained dithienoarsoles, including a main-chain type polymer, show luminescence not only in solution but also in the solid state.