Optimized Synthesis and Simple Purification of 2,5‐Diamino‐thiophene‐3,4‐dicarboxylic Acid Diethyl Ester

Spectroscopic and Physicochemical Investigations of Azomethines with Triphenylamine Core towards Optoelectronics

Three new azomethines based on triphenylamine with two or three substituents were obtained. Chemical structure and purity were confirmed by ¹H NMR, FTIR elemental analysis and mass spectroscopy. The investigations were focused on the relationship between chemical structure and properties important for optoelectronic materials. Thus, the studies of thermal, optical and electrochemical properties were carried out based on differential scanning calorimetry, thermogravimetric analysis, electronic absorption, photoluminescence and cyclic voltammetry measurements. The ongoing consideration of experimental results was complemented by theoretical calculations using the density functional theory method. The donor activity of obtained compounds was tested in bulk-heterojuntion photovoltaic cells with structure ITO/PEDOT:PSS/imine:PCBM/Al and ITO/PEDOT:PSS/imine:P3HT:PCBM/Al). The effect of the presence of the amino-thiophene-3,4-dicarboxylic acid diethyl ester groups and various number of hexyloxyphenyl units on imines properties was demonstrated.

Synthesis and Characterization of New Conjugated Azomethines End-Capped with Amino-thiophene-3,4-dicarboxylic Acid Diethyl Ester

A new series of thiophene-based azomethines differing in the core structure was synthesized. The effect of the central core structure in azomethines on the thermal, optical and electrochemical properties was investigated. The obtained compounds exhibited the ability to form a stable amorphous phase with a high glass transition temperature above 100 °C. They were electrochemically active and undergo oxidation and reduction processes. The highest occupied (HOMO) and the lowest unoccupied molecular (LUMO) orbitals were in the range of −3.86–−3.60 eV and −5.46–−5.17 eV, respectively, resulting in a very low energy band gap below 1.7 eV. Optical investigations were performed in the solvents with various polarity and in the solid state as a thin film deposited on a glass substrate. The synthesized imines absorbed radiation from 350 to 600 nm, depending on its structure and showed weak emission with a photoluminescence quantum yield below 2.5%. The photophysical investigations were supported by theoretical calculations using the density functional theory. The synthesized imines doped with lithium bis-(trifluoromethanesulfonyl)imide were examined as hole transporting materials (HTM) in hybrid inorganic-organic perovskite solar cells. It was found that both a volume of lithium salt and core imine structure significantly impact device performance. The best power conversion efficiency (PCE), being about 35–63% higher compared to other devices, exhibited cells based on the imine containing a core tiphenylamine unit.

Synthesis and in vitro biological evaluation of novel diaminothiophene scaffolds as antitumor and anti-influenza virus agents. Part 2

Herein, we report the synthesis and biological evaluation of a novel series of diethyl 2,5-diaminothiophene-3,4-dicarboxylate (DDTD) derivatives as antitumor and anti-influenza virus agents.

Ambipolar azomethines as potential cathodic color switching materials

The electrochemical oxidation and reduction reversibility along with the electrochemically mediated color change of triad azomethines were contingent on the central aromatic.

Synthesis and characterization of aza-bridged thiophene–pyrrole dyads and their isomers

Aza-bridged thiophene-pyrrole dyads were synthesized and characterized. Thiophenes substituted with electron-withdrawing groups (EWGs) were used as building blocks for the framework. However, an unprecedented cyclization occurred, and a thieno[2,3-d]pyrimidine derivative (4) was obtained in the reaction between 2,5-diamino-3,4-dicyanothiophene (1) and 3,5-diiminoisoindoline (3), whereas the reaction between 2,5-diamino-3,4-dicarboxylic acid ethyl ester (2) and 3 produced the desired dyad (5). The structures of 4 and 5 were unambiguously characterized by X-ray diffraction. Compound 5 is the first example of a core-modified azadipyrromethene, and the electronic interaction between the thiophene and pyrrole moieties was estimated with several spectroscopies. Several kinds of aryl groups can be attached at the terminal amino moiety of 4, and their unique absorption properties were also revealed.

Towards electrochromic devices having visible color switching using electronic push-push and push-pull cinnamaldehyde derivatives

A series of symmetric and unsymmetric conjugated azomethines derived from cinnamaldehyde and 2,5-diaminothiophene-3,4-dicarboxylic acid diethyl ester were prepared. The optical, electrochemical, and spectroelectrochemical properties of the electronic push-pull and push-push triads were investigated. Their properties could be tuned contingent on the cinnamaldehyde's electron withdrawing and donating substituents. The push-push symmetric derivative exhibited positive solvatochromism with the absorbance spanning some 31 nm, depending on the solvent polarity. Solvent dependent spectroelectrochemistry was also found for the symmetric push-push azomethine. The color of the neutral state and radical cation spanned 215 nm. The most pronounced color transition of the purple colored material was found in dimethyl sulfoxide (DMSO), where the color bleached with electrochemical oxidation. This was a result of the absorbance shifting into the near infrared (NIR) and not from decomposition of the azomethine. Electrochromic devices with the azomethines possessing desired reversible oxidation and color changes in the visible were fabricated and tested to demonstrate the applicability of these azomethine triads in devices.

Conjugated 4-methoxybipyrrole thiophene azomethines: synthesis, opto-electronic properties, and crystallographic characterization

In the search of functional materials with improved electrochromic properties, thiophenes and asymmetric bipyrroles have been conjugated with azomethine units. 4-Methoxy-2,2'-bipyrroles 3-6 were first synthesized by a general route from 4-hydroxyproline and converted subsequently to dialdehydes 8-15, which underwent condensations with different aminothiophenes to provide azomethine conjugates 14-18 and 20-22. The crystallization and X-ray analysis of 20 showed the heterocycles and azomethine bonds were all co-planar with the heterocycles adopting an anti-parallel arrangement. These configurations result in extended conjugation and enhanced opto-electronic properties of the azomethines. Oxidation potential (E(pa)) was tailored by modification of the substitution pattern of the terminal thiophenes and central pyrroles of the azomethines. The combined low E(pa) and extended azomethine degree of conjugation resulted in stark color transitions occurring between their neutral and oxidized states. Reversible color formation was induced both electrochemically and by doping/de-doping with trifluoroacetic acid/triethylamine.