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Dibromoderivatives of benzofused chalcogen-nitrogen heterocycles are important precursors in the synthesis of various photovoltaic materials. 4,7-Dibromobenzo[d][1,2,3]thiadiazole is a practically unexplored compound in this series. In this communication, it was shown that the nucleophilic substitution of 4,7-dibromobenzo[d][1,2,3]thiadiazole with morpholine gave selectively 4-substituted product—4-(7-bromobenzo[d][1,2,3]thiadiazol-4-yl)morpholine. The structure of the newly synthesized compound was established by means of elemental analysis, high resolution mass-spectrometry, 1H, 13C NMR, and IR spectroscopy, mass-spectrometry, and X-ray analysis.

A new synthetic pathway to four substituted imidazoles from readily available 2-((4-aryl(thienyl)-5H-1,2,3-dithiazol-5-ylidene)amino)phenols has been developed. Benzo[d]oxazol-2-yl(aryl(thienyl))methanimines were proved as key intermediates in their synthesis. The formation of an imidazole ring from two methanimine derivatives likely includes the opening of one benzoxazole ring followed by ring closure by intermolecular nucleophilic attack of the N-methanimine atom to a carbon atom of another methanimine.

This paper presents an improved synthesis of 4,7-dibromobenzo[d][1,2,3]thiadiazole from commercially available reagents. According to quantum-mechanical calculations, benzo[d][1,2,3]thiadiazole (isoBTD) has higher values of ELUMO and energy band gap (Eg), which indicates high electron conductivity, occurring due to the high stability of the molecule in the excited state. We studied the cross-coupling reactions of this dibromide and found that the highest yields of π-spacer–acceptor–π-spacer type compounds were obtained by means of the Stille reaction. Therefore, 6 new structures of this type have been synthesized. A detailed study of the optical and electrochemical properties of the obtained π-spacer–acceptor–π-spacer type compounds in comparison with isomeric structures based on benzo[c][1,2,5]thiadiazole (BTD) showed a red shift of absorption maxima with lower absorptive and luminescent capacity. However, the addition of the 2,2′-bithiophene fragment as a π-spacer resulted in an unexpected increase of the extinction coefficient in the UV/vis spectra along with a blue shift of both absorption maxima for the isoBTD-based compound as compared to the BTD-based compound. Thus, a thorough selection of components in the designing of appropriate compounds with benzo[d][1,2,3]thiadiazole as an internal acceptor can lead to promising photovoltaic materials.

Four new D-A-&pi, A metal-free organic sensitizers for dye-sensitized solar cells (DSSCs), with [1,2,5]thiadiazolo[3,4-d]pyridazine as internal acceptor, thiophene unit as &pi, spacer and cyanoacrylate as anchoring electron acceptor, have been synthesized. The donor moiety was introduced into [1,2,5]thiadiazolo[3,4-d]pyridazine by nucleophilic aromatic substitution and Suzuki cross-coupling reactions, allowing design of D-A-&pi, A sensitizers with the donor attached to the internal heterocyclic acceptor not only by the carbon atom, as it is in a majority of DSSCs, but by the nitrogen atom also. Although low values of power conversion efficiency (PCE) were found, a few important consequences were identified: (i) poor PCE data can be attributed to high electron deficiency of the internal [1,2,5]thiadiazolo[3,4-d]pyridazine acceptor due to lower light harvesting by the dye, (ii) the manner in which the donor was attached to the internal acceptor (by carbon or nitrogen) did not play an essential role in the photovoltaic properties of the dyes, (iii) dyes based on the novel donor 2,3,4,4a,9,9a-hexahydro-1H-1,4-methanocarbazolyl and 9-(p-tolyl)-2,3,4,4a,9,9a-hexahydro-1H- carbazole moieties showed similar photovoltaic properties to dyes based on the well-known 4-(p-tolyl)-1,2,3,3a,4,8b-hexahydrocyclopenta[b]indolyl building block, which opens the door for further optimization potential of new dye families.

The 11a,12-dihydrobenzo[b]benzo[5,6][1,4]oxazino[2,3-e][1,4]oxazine heterocyclic system has been used in the construction of heteropropellanes, which attracted much attention not only on the possible modification of drugs, but also for novel materials with unusual and important physical properties. In this communication, the reaction of ethyl 2-(hydroxyimino)propanoate 1 with disulfur dichloride and o-aminophenol, which gave ethyl 11a,12-dihydrobenzo[b]benzo[5,6][1,4]oxazino[2,3-e][1,4]oxazine-5a(6H)-carboxylate in moderate yield, was described. The structure of the newly synthesized compound was established by means of elemental analysis, high resolution mass-spectrometry, 1H, 13C NMR and IR spectroscopy, mass-spectrometry and X-ray analysis.

Galectin-3 (Gal-3) is a carbohydrate binding protein that is overexpressed in several types of cancers, including pancreatic cancer, which makes it a good target for both imaging and therapeutic drug design. A ligand library specialized for 18F positron emission tomography (PET) has been investigated with molecular dynamics (MD) and free energy methods to determine the relative binding energies of various potential ligands. Our results suggest that traditional docking methods can give good results when complemented by molecular dynamics and free energy methods for these types of ligands. Available experimental binding affinities for a small number of the tested compounds show very good agreement with the calculated energies and provide the rational approach for design of Gal-3 ligands with even higher affinity.

Dihalogenated derivatives of [1,2,5]chalcogenadiazolo[3,4-d]pyridazines are of interest as precursors for both photovoltaic materials and biologically active compounds. In this communication, 4,7-dichloro[1,2,5]oxadiazolo[3,4-d]pyridazine 1-oxide was prepared via the reaction of 3,6-dichloro-5-nitropyridazin-4-amine with oxidizing agents; the best yield of the target compound was achieved in the reaction with (diacetoxyiodo)benzene in benzene by heating at reflux for two hours. The structure of the newly synthesized compound was established by means of 13C-NMR and IR spectroscopy, mass-spectrometry and elemental analysis.