New thiophene- and phenothiazine-containing chalcones: Synthesis, and electrochemical properties

Abstract

Among the conjugated systems used in design of electronic devices based on organic materials the derivatives of carbazole and phenothiazine occupy are of key importance due to their high thermal stability, hole conductivity and light emission in various spectral regions when used in OLEDs and electrochromic devices, and to hole conductivity [1][2][3][4]. Phenothiazine contains electron-rich atoms N and S atoms, possesses a low oxidation potential, and is capable to form stable cation-radicals. The unique electronic and optical characteristics of phenothiazine proceed from its nonplanar geometry providing thereby the possibility to obtain π-packed aggregates and intermolecular excimers [5]. It has been established in our previous research that chalcones prepared on the base of carbazole, phenothiazine, and their substituted derivatives appeared to be good for creation of electrochromic polymer films [6][7][8]. It is also known that chalcones containing various aromatic fragments in their structure possess nonlinear optical properties indispensable for creation of optoelectronic devices, like electro-optic modulators, optical switches, lightemitting sources, etc. [9, 10]. Therefore it is expedient to synthesize new chalcone series including in their structure various carbo-and heterocyclic fragments and to examine their physicochemical properties, first, from the viewpoint of using them for preparation of polymer compounds, and second from the standpoint of tuning their electronic and optical characteristics by modifying the chemical structure.In this study there is presented the synthesis and the investigation of physicochemical properties of chalcones IX-XII (see the scheme) containing conjugation chains formed by combinations of various carbo-and heterocyclic fragments. For preparation of these chalcones we have initially synthesized two already known methyl ketones I [11] and II [12], after that a thiophene fragment was introduced into their structure. At the first stage of the synthesis the Vilsmeier-Haak-Arnold reaction was carried out to prepare compounds III and IV, their cyclization with chloroacetone in the presence of Na 2 S afforded methyl ketones V and VI used further as methylene components in the synthesis of chalcones [11,13,14].Refluxing of the obtained methyl ketones V and VI with 4-(10N-phenothiazin-10-yl)-and 4-(9N-carbazol-9-yl)benzaldehydes VII and VIII in the alkaline alcohol solution gave rise to the target chalcones IX-XII. Thus prepared chalcones are the dark red or orange crystalline substances, well soluble in common organic solvents, and their solutions in dichloromethane possess a pronounced yellow and yellow-green fluorescence, and in hexane -a blue one. UV absorption and fluorescence spectra of compounds V, VI and IX-XII were recorded for their solutions in chloroform. Stokes shifts were estimated from the data of absorption and emission spectra. On the basis of the value of the longest absorption wavelength (λ onset ) the width of the forbidden band gap (E g opt ) was calculated [15...

Luminescent Mono‐, Di‐ and Trisubstituted 2,4,6‐Triphenylpyridine‐Based Molecules: Synthesis and Properties

“…This means, the compounds polymerize due to the presence of carbazole substituents. These results are consistent with earlier studies carried out by the authors [58,59] …”

“…These results are consistent with earlier studies carried out by the authors. [58,59] For the compounds 6-9, the first irreversible oxidation step is observed at 1.15, 1.00, 1.25, and 1.08 V. The lower voltage of the oxidation onset for the pyridines 7 and 9 is explained by a strong π-conjugation and the presence of a good electrondonating N,N-diphenylamino-substituent.…”

Synthesis of red emitting triphenylamine derived NLOphoric D–π–A molecules: photophysical, and viscosity sensing studies

“…Figure 1 represents normalized absorption and emission spectra for all the four chromophores in seven different solvents. The first absorption smaller peak at around 372 nm is due to the π-π* transition of compound 2 [61] and the second peak near 500 nm is due to the intramolecular charge transfer transition (ICT). The red shifted absorption spectra were observed when the rhodamine-3-acetic acid group is attached to triphenylamine moiety.…”