The photon absorption edge in superconductors and gapped 1D systems

Opening of a gap in the low-energy excitations spectrum affects the power-law singularity in the photon absorption spectrum $A(\Omega)$. In the normal state, the singularity, $A(\Omega)\propto [D/(\Omega-\Omega_{\rm th})]^\alpha$, is characterized by an interaction-dependent exponent $\alpha$. On the contrary, in the supeconducting state the divergence, $A(\Omega)\propto (D/\Delta)^\alpha(\Omega-\tilde{\Omega}_{\rm th})^{-1/2}$, is interaction-independent, while threshold is shifted, $\tilde{\Omega}_{\rm th}=\Omega_{\rm th}+\Delta$; the ``normal-metal'' form of $A(\Omega)$ resumes at $(\Omega-\tilde{\Omega}_{\rm th})\gtrsim \Delta\exp(1/\alpha)$. If the core hole is magnetic, it creates in-gap states; these states transform drastically the absorption edge. In addition, processes of scattering off the magnetic core hole involving spin-flip give rise to inelastic absorption with one or several {\it real} excited pairs in the final state, yielding a structure of peaks in $A(\Omega)$ at multiples of $2\Delta$ above the threshold frequency. The above conclusions apply to a broad class of systems, e.g., Mott insulators, where a gap opens at the Fermi level due to the interactions.Comment: 6 pages, 5 figures; published versio

Diazatriphenylenes and their thiophene analogues: Synthesis and applications

This review highlights the recent advances in the field of the synthesis of diazatriphenylenes and their structural analogues, such as phenanthrenes, fused with the thiophene ring, and naphthalenes, condensed with two thiophene rings. Also applications of these compounds are considered. © ARKAT USA, Inc.The research was financially supported by the Russian Science Foundation (Project No. 16-13-10435) and the Russian Foundation for Basic Research (research project №. 17-03-00011-А)

5-(Methylidene)barbituric acid as a new anchor unit for dye-sensitized solar cells (DSSC)

Novel dyes bearing a 5-(methylidene)barbituric acid moiety as a new acceptor/anchor fragment were obtained and exhibited remarkable photophysical properties, according to a preliminary assessment of their sensitization activity as elements for dye-sensitized solar cells. © ARKAT-USA, Inc

(E)-2-(hydroxystyryl)-3-phenylquinazolin-4(3H)-ones: Synthesis, photochemical and luminescent properties

The new (E)-2-(hydroxyarilethenyl)-3-phenylquinazolin-4(3H)-ones with various substituents in phenyl fragment were synthesized. The effect of electron donor and acceptor substituents (±M) in quinazolinones on luminescence intensity and dual emission in 550-650-nm wavelength range was shown. The fact of the reversible photo/thermal E-Z isomerization for several substances was established. The (E)-2-(5-chloro-2-hydroxystyryl)-3-phenylquinazolin-4(3H)-one had shown the best combination of photochemical (E-Z isomerization) and photophysical properties. The (E)-2-(2-hydroxy-5-morpholinostyryl)-3-phenylquinazolin-4(3H)-one had revealed the best ESIPT-luminescence (Φrel = 5.3 %). © Arkat. All Rights Reserved.Russian Foundation for Basic Research, RFBR: 18-03-00112This work was supported by the Russian Foundation for Basic Research (grant 18-03-00112). Analytical studies were carried out using equipment of the Center for Joint Use SSpectroscopy and ?nalysis of Organic Compounds ? at the Postosvky Institute of Organic Synthesis of the Russian Academy of Sciences (Ural Branch)

An improved protocol for the preparation of 5, 11-dialkyl-6, 12-di(hetero)aryl-5, 11-dihydroindolo[3, 2-b]carbazoles and synthesis of their new 2, 8-dicyano-/2, 8-bis(benzo[d]thiazol-2-yl)-substituted derivatives

A number of 5, 11-dialkyl-6, 12-di(hetero)aryl-5, 11-dyhydroindolo[3, 2-b]carbazoles has been synthesized by modified method based on HBr catalyzed condensation of (hetero)aromatic aldehydes with indole in MeCN solution affording 5, 6, 11, 12-tetrahydroindolo[3, 2-b]carbazoles, that have been aromatized with I2 in DMF solution for 1 h at reflux, followed by alkylation of 5, 11-dihydro compounds. New 2, 8-dicyano-(10 examples) as well as 2, 8-bis(benzo[d]thiazol-2-yl)-substituted (5 examples) derivatives of these 5, 11-dyhydroindolo[3, 2-b]carbazoles have been obtained through their initial C2, 8-formylation, followed by treatment of dialdehydes with excess of hydroxylamine and dehydration of the formed aldoximes with acetic anhydride or by interaction with excess of 2-aminothiophenol in DMSO solution, respectively. © 2018 Arkat. All rights reserved.This research study was supported financially by the Russian Science Foundation (Project No. 16-13-10435)

A convenient approach to the design and synthesis of indolo[3,2-c]coumarins via the microwave-assisted Cadogan reaction

3-(4,5-Dimethoxy-2-nitrophenyl)coumarins bearing various substituents on the benzene ring of the coumarin system have been prepared from salicylaldehydes and 2-(4,5-dimethoxy-2-nitrophenyl)acetonitrile by means of the Perkin condensation. Further cyclization of these 3-aryl coumarins through the microwave-assisted Cadogan reaction afforded the corresponding indolo[3,2-c]coumarins in good to excellent yields. © 2013 Elsevier Ltd. All rights reserved

A New Family of Fused Azolo[1,5- A[pteridines and Azolo[5,1-b]purines

The nitration of azolo[1,5-a]pyrimidin-7-amines with several nitration agents (such as acetic nitric anhydride, nitronium tetrafluoroborate, and a mixture of concentrated nitric acid and sulfuric acid) has been investigated. It has been shown that, depending on the conditions, the nitration of pyrazolopyrimidin-7-amines bearing electron-withdrawing groups in the pyrazole ring leads to nitration products in the pyrimidine and/or pyrazole ring. The nitration of triazolo[1,5-a]pyrimidin-7-amines with "nitrating mixture"has been optimized, thus allowing us to obtain a series of 6-nitro[1,2,4]triazolo[1,5-a]pyrimidin-7-amines, followed by their reduction into the corresponding [1,2,4]triazolo[1,5-a]pyrimidin-6,7-diamines (yields 86-89%). The latter have been subjected to heterocyclization by a variety of electrophilic compounds (such as CS2, glyoxal, triethyl orthoformate) with the formation of five-or six-membered annulated cycles. Copyright © 2020 American Chemical Society.Russian Science Foundation, RSF: 19-13-00234The research was financially supported by the Russian Science Foundation (project no. 19-13-00234). Analytical studies were carried out using equipment of the Center for Joint Use “Spectroscopy and Analysis of Organic Compounds” at the Postovsky Institute of Organic Synthesis of UB RAS

Synthesis of aryl-substituted thieno[3,2-b]thiophene derivatives and their use for N,S-heterotetracene construction

Fiesselmann thiophene synthesis was applied for the convenient construction of thieno[3,2-b]thiophene derivatives. Thus, new 5- or 6-aryl-3-hydroxythieno[3,2-b]thiophene-2-carboxylates were obtained by condensation of 5- or 4-aryl-3-chlorothiophene-2-carbox-ylates, respectively, with methyl thioglycolate in the presence of potassium tert-butoxide. The saponification of the resulting esters, with decarboxylation of the intermediating acids, gave the corresponding thieno[3,2-b]thiophen-3(2H)-ones. The latter ketones were used to synthesize new N,S-heterotetracenes, namely 9H-thieno[2',3':4,5]thieno[3,2-b]indoles by their treatment with arylhydrazines in accordance with the Fischer indolization reaction. © 2019 Demina et al.; licensee Beilstein-Institut.Russian Foundation for Basic Research, RFBR: 18-33-20083This study was supported by the Russian Foundation for Basic Research, Grant No. 18-33-20083

Synthesis of 5-Methyl-1,2,4-Triazolo[1,5-а]Pyrimidin-7(4H)-One-a Semi-Product of the Synthesis of Antiviral Drug Triazide® in the Conditions of Microwave Excitation

This work was supported by the Russian Science Foundation (Ref. № 18-13-00365)

An Approach to the Construction of Benzofuran-Thieno[3,2- b]indole-Cored N,O,S-Heteroacenes Using Fischer Indolization

A series of 6H-benzofuro[2′,3′:4,5]thieno[3,2-b]indoles were readily synthesized from methyl 3-aminothieno[3,2-b]benzofuran-2-carboxylates using a one-pot procedure with Fischer indolization as the key step. At the same time, 3-aminothieno[3,2-b]benzofuran-2-carboxylates were prepared from 3-chlorobenzofuran-2-carbaldehydes in three steps, including replacement of the Cl atom at the C-3 position of these starting substrates onto the -SCH2CO2Me moiety, conversion of the CHO group at the C-2 position into the CN group, followed by base-promoted cyclization of the formed carbonitrile. The present route was elaborated by us because we failed to obtain directly the desired 3-aminothiophene-2-carboxylate by reaction of 3-chlorobenzofuran-2-carbonitrile with methyl thioglycolate in the presence of various bases. In turn, 3-chlorobenzofuran-2-carbaldehydes were prepared from benzofuran-3(2H)-ones following the Vilsmeier-Haack-Arnold reaction. © 2021 The Authors. Published by American Chemical Society.The research was financially supported by the Russian Science Foundation (project no. 18-13-00409)