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In this work, new D-π-A dyes bearing thieno[3,2- b ]indole, 7-(tert -butyl)thieno[3,2- b ]indole or benzo[ g ]thieno[3,2- b ]indole as an electron-donating part, 2,2′-bithiophene unit as π-linker and 2-cyanoacrylic acid as an electron acceptor-anchoring part have been readily synthesized and used for dye-sensitized solar cells (DSSCs). In addition, thermal stability, optical and electrochemical properties of these dyes were investigated. The DSSCs based on dyes IS-BTh exhibited values of PCE in the range of 3.43–4.41 % under AM 1.5 G irradiation. The highest PCE value of 4.41 % (J sc = 11.61 mA cm−2, V oc = 0.64 V, FF = 0.59) was achieved for DSSC based on dye IS-BTh-1 , bearing thieno[3,2- b ]indole as an electron-donating part. The temperature dependencies of the photovoltaic parameters for DSSC based on dye IS-BTh-1 were investigated. Three new D-π-A compounds were synthesized and used as photosensitizers for dye-sensitized solar cells (DSSCs), and the highest power conversion efficiency of 4.41 % was achieved for DSSC based on dye IS-BTh-1. [Display omitted] • Novel D-π-A thieno[3,2- b ]indole based photosensitizers were synthesized and used for dye-sensitized solar cells (DSSCs). • The effect at modifying thieno[3,2- b ]indole donor part in the structure of these dyes was investigated. • The highest PCE value of 4.41 % was achieved for DSSC based on dye IS-BTh-1 , bearing thieno[3,2- b ]indole as an electron-donating part. • The temperature dependencies of the photovoltaic parameters for DSSC based on dye IS-BTh-1 were investigated. [ABSTRACT FROM AUTHOR]

The synthesis of novel [1,2,4]triazolo[1,5- a ]pteridine (TPt) derivatives was carried out starting from [1,2,4]triazolo[1,5- a ]pyrimidine-6,7-diamines and 1,2-dicarbonyl compounds. For obtained TPt DFT/TD-DFT calculations were performed with subsequent complex photophysical and electrochemical studies. The substituent in the pyrazine ring of TPt framework proved to have a higher effect on photophysical properties than that in the triazole ring. The fluorescence quantum yields of studied compounds were generally low (3–23%). However, it was shown that some of TPt was sensitive to trace amounts of organic peroxides (about 100 ppm), which will make it possible to create test systems based on them. On the other hand, low-lying HOMO energy levels and the energy gap values of TPt (2.63 eV < E 0-0 < 2.97 eV) as well as the electron mobility in solid-state films measured by the conventional CELIV technique (approximately 10−4 cm2 V−1 s−1) make these materials promising for the further use in organic electronic devices. [Display omitted] • A number of new 2,7,8-R-[1,2,4]triazolo[1,5- a ]pteridine (TPt) have been synthesized. • The substituent in the triazole ring has a less significant effect on the photophysical properties. • 7,8-diphenyl substituted TPt derivatives exhibit the highest fluorescence quantum yields. • The electron mobility of the TPt measured by the CELIV method was 10−4 cm2V−1s−1. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fused coumarin-thieno[3,2- b ]indole compounds were readily prepared in three steps. • Thieno[3,2- b ]indole part of these molecules was formed thought Fischer indolization. • The synthesis was carried out from available 4-hydroxycoumarins. A series of 6 H ,7 H -chromeno[3′,4′:4,5]thieno[3,2- b ]indol-6-ones, bearing thieno[3,2- b ]indole and coumarin parts in their fused molecules, were readily prepared using one-pot procedure based on reaction of 3-aminothieno[3,2- c ]coumarins, in situ formed from 3-aminothieno[3,2- c ]coumarin-2-carboxylates, with arylhyrazines according to the Fischer indole synthesis. In turn, the synthesis of methyl 3-aminothieno[3,2- c ]coumarin-2-carboxylates were carried out in two steps from available 4-hydroxycoumarins. To this end, 4-hydroxycoumarins were successively treated with POCl 3 -DMF complex and hydroxylamine hydrochloride to obtain 4-chloro-3-cyanocoumarins. The latter substrates further reacted with methyl thioglycolate in the presence of NaOMe to give the required 3-aminothiophene-2-carboxylate precursors. [ABSTRACT FROM AUTHOR]

During this study, series of benzo[4,5]thieno[3,2- b indoles, pyrido[3′,2':4,5]thieno[3,2- b indoles and pyrazino[2′,3':4,5]thieno[3,2- b indoles were efficiently synthesized from benzo- and pyrido- or pyrazino-fused 3-aminothiophene-2-carboxylates, respectively, using one-pot two-step strategy based on the Fischer indolization reaction. The essence of this synthetic approach is acid-promoted reaction of the 3-aminothiophene intermediates, in situ generated from the corresponding ring-fused 3-aminothiophene-2-carboxylates, with arylhydrazines to give arylhydrazones of thiophen-3(2 H)-ones, followed by their indolization to afford thieno[3,2- b indole-cored molecules. Image 1 • Ring-annulated thieno[3,2- b indoles were readily synthesized by one-pot procedure. • The synthesis was performed using easily accessible starting materials. • The Fischer indolization reaction is a key transformation of the current approach. [ABSTRACT FROM AUTHOR]

• Preparation of thieno[3,2- b ]indole derivatives by easy to perform synthetic procedure. • Generation of 3-aminothiophene intermediates from 3-aminothiophene-2-carboxylates. • 3-Aminothiophenes are converted to thieno[3,2- b ]indoles using Fischer indolization. • Starting 3-aminothiophene-2-carboxylates are easily accessible substrates. A convenient protocol for one-pot synthesis of thieno[3,2- b ]indoles, bearing aromatic, thien-2-yl or styryl fragments at C-2 position, from easily accessible 5-substituted 3-aminothiophene-2-carboxylates using the Fischer indolization reaction, was developed during this study. Two main steps of this approach are the saponification of the starting 3-aminoesters with sodium hydroxide and next treatment of the crude 3-aminoacids sodium salts with arylhydrazines in glacial acetic acid solution. The latter step includes in situ decarboxylation of the freed 3-aminothiophene-2-caboxylic acids to the 3-aminothiophenes and their acid promoted reaction with arylhydrazines to initially form arylhydrazones of 5-substituted thiophene-3(2 H)-ones, which smoothly cause indolization to afford the desired thieno[3,2- b ]indoles. [ABSTRACT FROM AUTHOR]