Functional Oligothiophenes: Molecular Design for Multidimensional Nanoarchitectures and Their Applications

Synthesis and optoelectronic properties of benzodithiophene-based conjugated polymers with hydrogen bonding nucleobase side chain functionality

Nucleobase functionalities in conjugated, alternating copolymers participate in interbase hydrogen bonding, which promotes molecular assembly and organization in thin films and enhances optical and electronic properties.

Optimal strategy based on radiation chemistry for facile and direct synthesis of poly(3-thiophene acetic acid) polymers in water and dichloromethane

γ-Induced polymerization was used as a novel method to easily synthesize nanostructured PTAA polymers in water and dichloromethane.

Facile polymerization method for poly(3,4-ethylenedioxythiophene) and related polymers using iodine vapour

A simple polymerization at room temperature using iodine vapour for preparation of PEDOT and PProDOT and their soluble derivatives in neat form.

Recent advances in poly(3,4-ethylenedioxyselenophene) and related polymers

This review highlights the recent progress in synthesis, properties, applications and future outlook of PEDOS based conjugated polymers.

Cu-Catalyzed one-pot synthesis of thiochromeno-quinolinone and thiochromeno-thioflavone via oxidative double hetero Michael addition using in situ generated nucleophiles

A copper catalyzed three-component synthesis of π-conjugated tetracyclic thiochromeno-quinolinone and thiochromeno-thioflavone was established via oxidative double hetero Michael addition using in situ generated nucleophiles.

Room temperature nickel-catalyzed cross-coupling of aryl-boronic acids with thiophenols: synthesis of diarylsulfides

A mild and easy to operate NiCl₂/2,2′-bipyridine-catalyzed cross-coupling of thiophenols with arylboronic acids has been developed for the synthesis of symmetric and unsymmetric diarylsulfides at room temperature and in air.

Visible-light induced decarboxylative coupling of redox-active esters with disulfides to construct C–S bonds

A novel method has been established for the construction of C–S bonds using redox-active esters with disulfides in the presence of Ru-photoredox catalyst.

Diels–Alder reaction of tetraarylcyclopentadienones with benzo[b]thiophene S,S-dioxides: an unprecedented de-oxygenation vs. sulfur dioxide extrusion

The Diels–Alder adduct, dihydrodibenzothiophene S,S-dioxides underwent aromatization either through de-oxygenation or extrusion of sulfur dioxide to furnish substituted dibenzothiophenes or benzenes.

A mechanistic study of the activation of small molecules (H2 and C2H2) by group 14 analogues of selenophene

In this study, the reactivity influenced by group 14 elements (E = C, Si, Ge, Sn, and Pb), which are used as substituents in heterocyclic five-membered rings, was theoretically examined by using density functional theory (B3PW91/def2-SVP).

Rongalite as a sulfone source: a novel copper-catalyzed sulfur dioxide anion incorporation process

A novel copper-catalyzed sulfur dioxide anion incorporation cascade for the synthesis of 1-thiaflavanone sulfones has been disclosed using rongalite as an economic and safe sulfone source.

Poly(3,4-ethylenedioxyselenophene): effect of solvent and electrolyte on electrodeposition, optoelectronic and electrochromic properties

In this article, we report the effect of electropolymerization conditions such as solvent and supporting electrolyte on the redox, optoelectronic and electrochromic properties of PEDOS. Monomer EDOS was synthesized by new and simple route and its electropolymerization was investigated by employing six different combinations of solvent–electrolyte namely TBAClO₄/MeCN, TBAPF₆/MeCN, TBABF₄/MeCN, TBAClO₄/PC, TBAPF₆/PC and TBABF₄/PC. Further, the electrochemical, spectroelectrochemistry, morphology and electrochromic properties of resultant PEDOS films were systematically studied. A pronounced effect of both solvent and supporting electrolyte on the electropolymerization, redox, optoelectronic and electrochromic properties on PEDOS film is noted. Among all solvent–electrolyte systems, MeCN and TBAClO₄ were found to be the most suitable medium for electropolymerization of EDOS. Further, PEDOS films prepared in PC showed red shifted absorption maxima, narrow absorption peaks in UV-vis-NIR spectra, slightly more smooth morphologies, and high optical contrasts ratio and coloration efficiency in comparison to MeCN. PEDOS films prepared in TBABF₄/PC exhibited longer λ_max (670 nm), smooth morphology, and the highest optical contrasts ratio (44.6%) and coloration efficiency (141.8 cm² C⁻¹) compared to the other solvent–electrolyte medium.

In this article, we report the effect of electropolymerization conditions such as solvent and supporting electrolyte on the redox, optoelectronic and electrochromic properties of PEDOS.

Supramolecular Nanowires from an Acceptor-Donor-Acceptor Conjugated Chromophore

Oligothiophene derivatives have been extensively studied as p-type semiconducting materials in organic electronics applications. This work reports the synthesis, self-assembly and photophysical properties of acceptor-donor-acceptor (A-D-A)-type oligothiophene derivatives by end-group engineering of quaterthiophene (QT) with naphthalene monoimide (NMI) chromophores that are further connected to a trialkoxy benzamide wedge. Conjugation to the NMI units reduces the HOMO-LUMO gap significantly, and consequently the absorption spectrum exhibits a bathochromic shift of about 50 nm compared with QT. Furthermore, extended H-bonding interactions among the amido groups of the peripheral wedges produce entangled fibrillar nanostructures and gelation in hydrocarbon solvents such as methylcyclohexane, wherein the A-D-A chromophore exhibits typical H-aggregation. On the contrary, the fact that the same chromophore, lacking only the amido units, does not produce gels or H-aggregates indicates strong impact of H-bonding on the self-assembly. Computational studies revealed the electronic properties of the chromophore and predicted the geometry of a dimer in the H-aggregate that reasonably matches with the experimental results. Bulk electrical conductivity measurements determined an excellent conductivity of 2.3×10^-2  S cm^-1 for the H-aggregated system (OT-1), which is two orders of magnitude higher than that of the same chromophore lacking the amido groups (OT-2).

Copper-Mediated Deacylative Coupling of Ynones via C-C Bond Activation under Mild Conditions

The intermolecular deacylative coupling of unstrained ynones via C-C bond activation was accomplished by a CuCl-bpy system under mild reaction conditions. This protocol features facile cleavage of the C-C bond at room temperature, broad substrate scope, and efficient construction of important symmetric and unsymmetrical 1,3-diyne adducts through homo or cross coupling of ynones, respectively. The preliminary mechanistic investigations indicated that an acyl copper(III) complex is likely involved in this process.

Effects of cis-trans Conformation between Thiophene Rings on Conductance of Oligothiophenes

Oligothiophenes have been established as important π-conjugated frameworks in organic electronics and molecular electronics. Although oligothiophenes possess the rotational flexibility of thiophene rings, the effects of cis-trans conformations on their electrical conductance have not been investigated yet. To investigate the effects of cis-trans conformations between thiophene rings on the conductance of oligothiophenes, we performed first-principles transport calculations. The conductance of the cis-oligothiophene was calculated to be higher than that of trans-oligothiophene, because the highest occupied molecular orbital was closer to the Fermi level of the gold electrode in the cis isomer than the trans isomer. This prediction was confirmed through mechanically controllable break junction measurements and fitting of the current-voltage characteristics for the newly synthesized, insulated oligothiophenes with controlled cis-trans conformations. This study demonstrates that cis- and trans-conformations can affect the electrical properties of oligothiophene frameworks and can potentially be used to control the electronic structure of long oligothiophene molecular wires.

Superelectrophilic-Initiated C-H Functionalization at the β-Position of Thiophenes: A One-Pot Synthesis of trans-Stereospecific Saddle-Shaped Cyclic Compounds

Superelectrophilic-initiated direct C-H functionalization of thiophenes at the β-position was developed. A series of trans-stereospecific [2,1-a]-IF-thiophene-fused cyclic compounds (4) with saddle-shaped structure were prepared in 17-30% yields through a one-pot superelectrophilic Friedel-Crafts reaction of dihydroindenofluorene with thiophene derivatives. From the crystal packing analyses of 4a, its skeleton shows both strong intermolecular π-π stacking and C-H···π stacking. Furthermore, the ring-dependent photophysical properties of 4 were confirmed by UV-vis absorption and photoluminescence spectroscopy as well as through the study of their fluorescence quantum yield.

Convenient one-pot access to 2H-3-nitrothiochromenes from 2-bromobenzaldehydes, sodium sulfide and β-nitrostyrenes

An efficient synthesis of 2H-3-nitrothiochromenes via a cascade reaction was established. Starting from commercially available o-bromobenzaldehydes and β-nitrostyrenes with sodium sulfide nonahydrate as an inexpensive sulfur source, various substituted thiochromenes were synthesized with high functional group tolerance without any added transition metal catalyst or additive.

Highly Planar and Completely Insulated Oligothiophenes: Effects of π-Conjugation on Hopping Charge Transport

Elucidating the nature of long-range intramolecular charge transport in π-conjugated molecules is of great importance for the development of organic electronic materials. However, the effects of the degree of π-conjugation on the hopping charge transport have not been experimentally explored so far owing to the lack of π-conjugated backbones with different conjugation degrees and several-nanometer lengths. Here we develop highly planar and completely insulated oligothiophenes between 0.85 and 9.64 nm in length. As compared to distorted oligothiophenes, single-molecule conductance measurements of the planar molecules show (i) a smaller activation energy and larger electrical conductance in the hopping transport regime and (ii) a shift in crossover between tunneling and hopping conduction toward a short molecular length. Theoretical calculations indicate that small reorganization energies and narrow energy gaps derived from the planar backbones result in these superior characteristics. This study reveals that the planarity of π-conjugation has significant advantages for hopping charge transport.

Alternating Tetrafluorobenzene and Thiophene Units by Direct Arylation for Organic Electronics

Direct arylation represents an attractive alternative to the conventional cross-coupling methods because of its step-economic and eco-friendly advantages. A set of simple D-A oligomeric molecules (F-3, F-5, and F-7) by integrating thiophene (T) and tetrafluorobenzene (F4B) as alternating units through a direct arylation strategy is presented to obtain high-performance charge-transporting materials. Single-crystal analysis revealed their herringbone packing arrangements driven by intensive C-H⋅⋅⋅π interactions. An excellent hole-transporting efficiency based on single-crystalline micro-plates/ribbons was witnessed, and larger π-conjugation and D-A constitution gave higher mobilities. Consequently, an average mobility of 1.31 cm²  V^-1  s^-1 and a maximum mobility of 2.44 cm²  V^-1  s^-1 for F-7 were achieved, providing an effective way to obtain high-performance materials by designing simple D-A oligomeric systems.

Recent Progress in Molecular Design of Fused Ring Electron Acceptors for Organic Solar Cells

The quest for sustainable energy sources has led to accelerated growth in research of organic solar cells (OSCs). A solution-processed bulk-heterojunction (BHJ) OSC generally contains a donor and expensive fullerene acceptors (FAs). The last 20 years have been devoted by the OSC community to developing donor materials, specifically low bandgap polymers, to complement FAs in BHJs. The current improvement from ≈2.5% in 2013 to 17.3% in 2018 in OSC performance is primarily credited to novel nonfullerene acceptors (NFA), especially fused ring electron acceptors (FREAs). FREAs offer unique advantages over FAs, like broad absorption of solar radiation, and they can be extensively chemically manipulated to tune optoelectronic and morphological properties. Herein, the current status in FREA-based OSCs is summarized, such as design strategies for both wide and narrow bandgap FREAs for BHJ, all-small-molecule OSCs, semi-transparent OSC, ternary, and tandem solar cells. The photovoltaics parameters for FREAs are summarized and discussed. The focus is on the various FREA structures and their role in optical and morphological tuning. Besides, the advantages and drawbacks of both FAs and NFAs are discussed. Finally, an outlook in the field of FREA-OSCs for future material design and challenges ahead is provided.

Comparative Computational Study of Electronic Excitations of Neutral and Charged Small Oligothiophenes and Their Extrapolations Based on Simple Models

This work reports electronic excitation energies of neutral and charged oligothiophenes (OT n ) with repeat unit n = 2-6 computed by routinely used semiempirical and time-dependent density functional theory (TD-DFT) methods. More specifically, for OT n , OTn +, and OTn -, we calculated vertical transition energies for electronic absorption spectroscopy employing the Zerner's version of intermediate neglect differential overlap method for structures optimized by the PM6 semiempirical method and the TD-DFT method with three different functionals, B3LYP, BVP86, and M06-2X, for structures optimized by the ground-state DFT method employing the same functionals. We also calculated vertical transition energies for the emission spectroscopy from the lowest singlet excited states by employing the TD-DFT method for the structures optimized for the lowest singlet excited states. In addition to computational results in vacuum, solution phase data calculated at the level of polarizable continuum model are reported and compared with available experimental data. Most of the data are fitted reasonably well by two simple model functions, one based on a Frenkel exciton theory and the other based on the model of independent electrons in a box with sinusoidal modulation of potential. Despite similar levels of fitting performance, the two models produce distinctively different asymptotic values of excitation energies. Comparison of these with available experimental and computational data suggests that the values based on the exciton model, while seemingly overestimating, are closer to true values than those based on the other model. This assessment is confirmed by additional calculations for a larger oligomer. The fitting parameters offer new means to understand the relationship between electronic excitations of OTs and their sizes and suggest the feasibility of constructing simple coarse-grained exciton-bath models applicable for aggregates of OTs.

Synthesis of α,α’-linked penta- and septaheterocycles by tandem Suzuki coupling

The controlled synthesis of oligoaromatics can provide materials of wide utility. Here, we describe the preparation of higher order oligoheterocycles via a tandem Suzuki cross-coupling protocol. This method has allowed for the iterative construction of fluorescent [Formula: see text],[Formula: see text]-linked penta- and septaheterocyclic systems with modification of the terminal moiety allowing for fine-tuning of the emission features.

Donor-Acceptor-Donor Copolymers with 3,4-Ethylenedioxythiophene Moiety: Electropolymerization and Effect on Optoelectronic and Electrochromic Properties

Three random copolymers PE- co -M1, PE- co -M2, and PE- co -M3 were obtained by electrochemical polymerization of donor-acceptor-donor monomers M1, M2, and M3 with 3,4-ethylenedioxythiophene moiety, respectively, using a 1:1 molar ratio of the corresponding monomers, to find new properties and a more effective way to control the optoelectronic properties in conjugated system. For comparison purpose, polymers P1, P2, and P3 were prepared from the corresponding monomer units M1-M3, respectively, by electrochemical polymerization. We also present efficient synthesis, characterization, and comparative density functional theory (DFT) calculations of the monomers M1-M3 and polymers P1-P3. Cyclic voltammetry, spectroelectrochemistry, and electrochromic properties of all of the polymers P1-P3 and copolymers PE- co -M1, PE- co -M2, and PE- co -M3 were carried out and a throughout comparison was made. We have shown that electrochemical copolymerization is a powerful strategy to tune the highest occupied molecular orbital energy level, band gap, and color of the copolymer. Thus, this finding clearly indicates that the copolymers show significantly different optoelectronic properties compared to their constituent polymers.