Symmetrical and unsymmetrical azomethines with thiophene core: structure–properties investigations

Abstract

Unsymmetrical and symmetrical azomethines were obtained using the condensation reaction of diamino-thiophene-3,4 dicarboxylic acid diethyl ester with 4-(1-pyrrolidino)benzaldehyde, fluorene-2-carboxaldehyde, 1-methylindole-3carboxaldehyde, and benzothiazole-2-carboxaldehyde. Their thermal, optical, and electrochemical properties were investigated, and the results were supported by calculations using the density functional theory. The studied compounds melted in the range of 170-260°C and can be converted into amorphous materials with high glass transition temperatures between 76 and 135°C. They were thermally stable up to 220-300°C. All imines were electrochemically active and exhibited low energy band gaps below 2 eV (except for one imine with E g = 2.39 eV) determined on the basis of cyclic voltammetry. Most of the azomethines were emissive in solution and in the solid state. Some of them showed both S 1 (first excited state) emission and S 2 (second excited state) emission or only fluorescence from higher excited state, which is first time observed for azomethines. The imine with the most promising properties was tested in a light-emitting diode, and its ability for emission of light under external voltage was demonstrated.

Effect of Protonation on Optical and Electrochemical Properties of Thiophene–Phenylene-Based Schiff Bases with Alkoxy Side Groups

“…Azomethines (PAzs) are products of condensation (polycondensation) reaction between amines and aldehydes. Such reaction may proceed under mild conditions, using inorganic or organic catalysts or even without using any, as previously shown. , These types of materials were extensively studied due to their interesting thermal, electrical, and optical − properties and also due to the possible activity in some optoelectronic systems, such as bulk heterojunction photovoltaic cells, − perovskite solar cells, − organic light-emitting devices, , or electrochemical systems. , …”

Oxidant/Solvent-Controlled I2-Catalyzed Domino Annulation for Selective Synthesis of 2-Aroylbenzothiazoles and 2-Arylbenzothiazoles under Metal-Free Conditions

“…Compounds containing the benzothiazole motif have their wide occurrence in diverse pharmacological agents, natural products, and synthetic intermediates . In addition, the benzothiazole scaffold has been found frequently in other molecules such as industrial dyes , and functional materials . Consequently, the development of effective methods for constructing the benzothiazole skeleton has attracted considerable attention, and a number of versatile methods have been developed in recent years.…”

The Effect of Alkyl Substitution of Novel Imines on Their Supramolecular Organization, towards Photovoltaic Applications

“…This condensation reaction is easy to conduct, in mild conditions, catalyzed by organic or inorganic acids, or even without using any [ 8 , 9 ], on the contrary to carbon-carbon or vinylene-coupled compounds, which usually require stringent reaction conditions and rather extensive purification processes [ 10 ]. Due to the relatively simple synthesis route and promising properties, conjugated azomethines and polyazomethines have been investigated for applications in optoelectronic systems, like photovoltaic solar cells [ 11 , 12 , 13 ], electroluminescent diodes [ 14 , 15 ], or electrochromic systems [ 16 ]. Highly aromatic polyazomethines are rather insoluble, so their thin films may be obtained via gas-phase condensation or by chemical vapor deposition (CVD) [ 17 , 18 ].…”