A Bifunctional Bulky Thienothiophene Derivative; Synthesis, Electronic‐Optical Properties and OLED Applications

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).

Triphenylamine/4,4'-Dimethoxytriphenylamine-Functionalized Thieno[3,2-b]thiophene Fluorophores with a High Quantum Efficiency: Synthesis and Photophysical Properties

A wide series of 10 new triphenylamine (TPA)/4,4'-dimethoxytriphenylamine (TPA(OMe)₂)-functionalized thieno[3,2-b]thiophene (TT) fluorophores, 4a-e and 5a-e, bearing different electron-donating and electron-withdrawing substituents (-PhCN, -PhF, -PhOMe, -Ph, and -C₆H₁₃) at the terminal thienothiophene units were designed and synthesized by the Suzuki coupling reaction. Their optical and electrochemical properties were investigated by experimental and computational studies. Solid-state fluorescent quantum yields were recorded to be from 20 to 69%, and the maximum solution-state quantum efficiency reached 97%. Moreover, the photophysical characterization of the novel chromophores demonstrated a significant Stokes shift, reaching 179 nm with a bathochromic shift. They exhibited tuning color emission from orange to dark blue in solution and showed fluorescence lifetime reaching 4.70 ns. The relationship between triphenylamine (TPA)/4,4'-dimethoxytriphenylamine (TPA(OMe)₂)-derived triarylamines and different functional groups on thieno[3,2-b] thiophene units was discussed.