Copolymers of 3-Arylthieno[3,2-b]thiophenes Bearing Different Substituents: Synthesis, Electronic, Optical, Sensor and Memory Properties

Recent synthetic approaches towards thienothiophenes: a potential template for biologically active compounds

Heterocyclic compounds are attractive candidates because of their vast applications in natural and physical sciences. Thienothiophene (TT) is an annulated ring of two thiophene rings with a stable and electron-rich structure. Thienothiophenes (TTs) fully represent the planar system, which can drastically alter or improve the fundamental properties of organic, π-conjugated materials when included into a molecular architecture. These molecules possessed many applications including, pharmaceutical as well as optoelectronic properties. Different isomeric forms of thienothiophene showed various applications such as antiviral, antitumor, antiglaucoma, antimicrobial, and as semiconductors, solar cells, organic field effect transistors, electroluminiscents etc. A number of methodologies were adopted to synthesize thienothiophene derivatives. In this review, we have addressed different synthetic strategies of various isomeric forms of thienothiophene that have been reported during last seven years, i.e., 2016-2022.

A multifunctional thienothiophene member: 4-thieno[3,2-b]thiophen-3-ylbenzonitrile (4-CNPhTT)

Thieno[3,2-b]thiophene (TT) has been attracting significant attention in the field of organic electronics and optoelectronics. In this study, a useful building block of TT derivative 4-thieno[3,2-b]thiophen-3-ylbenzonitrile (4-CNPhTT), developed by our group and possessing a strong electron-withdrawing 4-CNPh moiety, is reviewed as it has been the source of the development of various organic electronic materials. Some optic and electronic properties are discussed based on electrochemical polymerization of 4-CNPhTT performed using cyclic voltammetry, and spectroelectrochemical measurements are conducted to investigate the optical variations of the polymer film upon doping. Moreover, 4-CNPhTT is clarified by scanning electron microscopy at different magnitudes ranging from 100 to 500 μm, supported by the single X-ray crystal structure. The thermal properties of 4-CNPhTT are investigated by thermal gravimetric and differential thermal analyses. All of the observed properties demonstrate that 4-CNPhTT has the potential of shedding light on the development of new materials for electronic and optoelectronic applications within the TT family.

Non-covalent modification of single wall carbon nanotubes (SWCNTs) by thienothiophene derivatives

Non-covalent functionalization of single wall carbon nanotubes (SWCNTs) has been conducted using several binding agents with surface π-interaction forces in recent studies. Herein, we present the first example of non-covalent functionalization of sidewalls of SWCNTs using thienothiophene (TT) derivatives without requiring any binding agents. Synthesized TT derivatives, TT-CN-TPA, TT-CN-TPA2 and TT-COOH-TPA, were attached directly to SWCNTs through non-covalent interactions to obtain new TT-based SWCNT hybrids, HYBRID 1-3. Taking advantage of the presence of sulfur atoms in the structure of TT, HYBRID 1, as a representative, was treated with Au nanoparticles for the adsorption of Au by sulfur atoms, which generated clear TEM images of the particles. The images indicated the attachment of TTs to the surface of SWCNTs. Thus, the presence of sulfur atoms in TT units made the binding of TTs to SWCNTs observable via TEM analysis through adsorption of Au nanoparticles by the sulfur atoms. Surface interactions between TTs and SWCNTs of the new hybrids were also clarified by classical molecular dynamic simulations, a quantum mechanical study, and SEM, TEM, AFM and contact angle (CA) analyses. The minimum distance between a TT and a SWCNT reached up to 3.5 Å, identified with strong peaks on a radial distribution function (RDF), while maximum interaction energies were raised to -316.89 kcal mol^-1, which were determined using density functional theory (DFT).

Beyond "Mega": Origin of the "Giga" Stokes Shift for Triazolopyridiniums

Over the past decade, fluorophores that exhibit "mega" Stokes shifts, defined to be Stokes shifts of greater than 100 nm, have gained considerable attention due to their potential technological applications. A subset of these fluorophores have Stokes shifts of at least 10,000 cm^-1, for whom we suggest the moniker "giga" Stokes shift. The majority of "giga" Stokes shifts reported in the literature arise from the twisted intramolecular charge transfer mechanism, but this mechanism does not fit empirical characterization of triazolopyridinium (TOP). This observation inspired a density functional theory (DFT) and time-dependent DFT study of TOP, and several related fluorophores, to elucidate the novel photophysical origin for the "giga" Stokes shift of TOP. The resulting computational models revealed that photoexcitation of TOP yields a zwitterionic excited state that undergoes significant structural relaxation prior to emission. Most notably, TOP has two orthogonal moieties in the ground state that adopt a coplanar geometry in the excited state. According to Hückel's rule, both the heterocycle and phenyl moieties of TOP should be aromatic in an orthogonal ground state. However, according to Baird's rule, these individual moieties should be anti-aromatic in the excited state. By relaxing to a coplanar conformation in the excited state, TOP likely forms a single aromatic system consisting of both the heterocycle and phenyl moieties.