Nguyen Hien

Thin films containing Mn-doped ZnS nanocrystals synthesised by chemical method and study of some of their optical properties

In this article, we present the optical properties of thin films containing Mn-doped ZnS nanocrystals synthesised by the chemical method. The ZnS nanoparticles within the polymer matrix (polyvinyl alcohol) were investigated by SEM and TEM images and analysed by X-ray diffraction. The effect of polymer concentration on the direct band gap of Mn-doped ZnS thin films was calculated from the data for absorption measurements. The values of the band gap are in the range of 3.73–3.90 eV. In addition, we discuss the photoluminescence of these films.

Synthesis and structure of some azolium salts

The reactions between benzimidazole, imidazole, or 1,2,4-triazole with either benzyl chloride or isopropyl bromide yielded 6 azolium salts, namely 1,3-dibenzylimidazolium chloride ( M1 ), 1,3-dibenzylbenzimidazolium chloride ( M2 ), 1,3-dibenzyl-1,2,4-triazolium chloride ( M3 ), 1,3-diisopropylimidazolium bromide ( M4 ), 1,3-diisopropylbenzimidazolium bromide ( M5 ), and 1,3-diisopropyl-1,2,4-triazolium bromide ( M6 ). These salts can be further used as the starting compounds for the synthesis of complexes based on N -heterocyclic carbenes for various applications. The structures of M1 ÷ M6 have been unambiguously determined by means of IR and 1 H NMR spectroscopic methods. Keywords. N -heterocyclic carbenes, azoles, azolium salts.

Structures of 2,5-diaryl- and 2,3,5,6-tetra[3,2-b]thiophene synthesized by the palladium-catalyzed Suzuki-Miyaura cross-coupling reaction

The crystal structures of 2,5-di(ethoxyphenyl)-3,6-dibromothieno[3,2- b ]thiophene ( I ) and 2,5-di(ethoxyphenyl)-3,6-diphenylthieno[3,2- b ]thiophene ( II ) have been studied in order to evaluate the planarity of these molecules. The aromatic systems introduced to the thieno[3,2- b ]thiophene core structure show a degree of rotation from 30.94° to 66.56°. The crystal packing of ( I ) are characterized by π×××π stacking, while in ( II ), C-H×××p and C-H×××O interactions are observed.

Synthesis and structural characterization of bipyridine ligands towards the application in dye-sensitized solar cells

An efficient synthetic route was developed to tailor bipyridine ligands basing on the palladium catalyzed Sonogashira cross-coupling of 4-bromo-2,2’-bipyridine. Structures of the modified bipyridines were elucidated by NMR and X-Ray diffraction analyses. It was shown that the introduced alkynes are co-planar with the bipyridine core, revealing an efficient effect of the substituent on the electronic properties of the ligand. Keywords. DSSC, 2,2’-bipyridine, dye sensitizers, palladium-catalyzed, Sonogashira.

AN ATTEMPT TO PLANARIZE 2,3,5,6-TETRAARYLTHIENO[3,2-b]THIOPHENE BY FeCl3-ASSISTED ANNULATION

Thieno[3,2-b]thiophene is a typical core structure in a number of conjugated organic opto-electronic materials. In this work, an attempt to planarize 2,3,4,6tetraarylthieno[3,2-b]thiophene based on the FeCl3 oxidative annulation was described. Thus, two cyclized 2,3,5,6-tetraarylthieno[3,2-b]thiophenes 5a and 5b were synthesized in moderate yields. NMR and HR-MS analysis indicated the annulation between only one pair of the phenyl substituents.

Aci-Quinone Compounds from Eugenoxyacetic Acid and Methyleugenol: Preparation and Reaction

A new aci-quinone compound, 4-(aci-nitro)-2-(methoxy)-5-(3-nitro-2-(nitrooxy)propyl)-cyclohexa-2,5dienone (2), an analog to 4-(aci-nitro)-2-(carboxymethoxy)-5-(3-nitro-2-(nitrooxy)propyl)-cyclohexa-2,5-dienone (1), was successfully synthesized and fully characterized by spectroscopic methods. The reactions of 1 and 2 with various reagents such as hydroxylamine, acetic anhydride, semicarbazide and thiosemicarbazide were examined. The structure of 11 obtained new compounds was established by IR, H NMR, C NMR, HMBC and MS spectra. It was shown that the unstable, sensitive aci-quinone structure of compounds 1 and 2 can exist in anhydrous organic solvents such as AcOEt, EtOH but in the presence of water, H, HO or at high temperatures, the aci-quinone structure of both 1 and 2 tendentiously transformed into the more stable nitro-phenol form.

Imidazolium-based ionic liquid as a green solvent for the Heck reaction between iodobenzene and styrene

An easily accessible ionic liquid, 1-hexyl-3-methylimidazolium bromide, was synthesized from n-hexyl bromide and N-methylimidazole under microwave irradiation condition, and characterized by 1 H and 13 C NMR, and MS. The ionic liquid was demonstrated to be an efficient and recyclable solvent for the Heck cross-coupling reaction between iodobenzene and styrene to form trans-stilbene as the principal product. The reaction was performed in the ionic liquid, using 5 mol% of PdCl 2 at 140 o C in the presence of triethylamine as the base. Reaction conversions of 60% and 97% were achieved after 7 hours, without and with using triphenylphosphine as an additive, respectively. The ionic liquid – PdCl 2 system could be reused in subsequent reaction without significant degradation in activity. Furthermore, using the ionic liquid as the reaction solvent in conjunction with microwave irradiation, the reaction rate was dramatically enhanced, with 98% conversion being achieved within 2 minutes.