Optoelectronic and biological quantification of semi-conducting,crimson europium chelates with fluorinated β-keto acid and N-donor ancillary ligands

Research on Chemical Intermediates - Five luminescent ternary and one binary Europium(III) complexes were synthesised with β-keto acid as primary ligand and neocuproine(neo),...     

Stereoselective synthesis of trans-3-functionalized-4-pyrazolo[5,1-b]thiazole-3-carboxylate substituted β-lactams: Potential synthons for diverse biologically active agents

Abstract

An efficient protocol for the stereoselective synthesis of pyrazolo[5,1-b]thiazole-3-carboxylate tethered β-lactam conjugates 8a–j from novel pyrazolo [5,1-b]thiazole-3-carboxylate substituted Schiff’s bases 6a–f is reported here. The reaction between various ketene precursors and novel Schiff’s bases 6a–f afforded exclusive formation of trans-β-lactams 8a–j. The substrate scope of this approach was investigated extensively by varying different groups (R, Z). All the novel compounds were characterized using various spectroscopic techniques, such as FT-IR, ¹H NMR, ¹³C NMR, elemental analysis, ¹³C NMR (DEPT-135), and mass spectrometry in representative cases. Single crystal X-ray crystallographic study of trans-ethyl 7-(1-(4-methoxyphenyl)-4-oxo-3-phenoxyazetidin-2-yl)-6-methyl-2-(methylthio)pyrazolo[5,1-b]thiazole-3-carboxylate 8a has confirmed the molecular structure and the stereochemical outcome. To the best of our knowledge, the synthesis of such types of Schiff’s bases and β-lactam conjugates has not been reported so far.     

Electrical conduction mechanism of polyvinylidenefluoride (PVDF) – polysulfone (PSF) blend film

The electrical conductivity of polyvinylidenefluoride (PVDF) – polysulfone (PSF) blend films have been measured by studying the I–V characteristics in the temperature range of 298–398 K. The results are shown by measuring the dependence of current on field, temperature, and blending compositions in the form of I–V characteristics and analysis has been made by interpretation of Poole–Frenkel, Schottky ln (J) vs. T plots, Richardson and Arrhenius plots. For individual polymers, the conduction mechanism observed to be a Poole–Frenkel type. On blending, the charge conduction appears to be the Schottky emission at lower temperature while Poole–Frenkel mechanism at higher temperature. The analysis of these results suggests that Pool–Frenkel mechanism is mainly responsible for the observed conduction. The conductivity was found to increase with an increase in the polysulfone concentration in the blend; it could be justified in terms of mobility of charge carriers. It is found that mobility of charge carriers increases with the increase in polysulfone concentration in the blend.     

Dye-sensitized solar cells concocted with dyes extracted from fresh and dried leaves of Henna using different solvents

Optical and Quantum Electronics - Nowadays, world is moving from conventional energy sources to non-conventional energy sources like solar energy, wind power, hydropower and those energy sources...     

Dielectric relaxation in polyvinylidenefluoride–polysulfone blends

Dielectric properties of polymer blend of polyvinylidenefluoride (PVDF) and polysulfone (PSF) of different wt. % have been studied to understand the molecular motion and their relaxation behavior in the frequency range of 100 Hz to 10 kHz at different temperatures between 30 and 190 °C. The dielectric constant of the blend decreased with frequency and increased with the increasing temperature and PSF content in the blend. The magnitude of dielectric loss also increased with increase in temperature and PSF content. The observed characteristic has been consistently explained in terms of dipolar motions and the plasticization effect brought about by blending of PSF with PVDF. At constant frequency and temperature, the blend follows a linear relationship between logarithm of their dielectric constant and different ratios of blend. The appearance of a peak for each concentration in dielectric loss suggests the presence of relaxing dipoles in the blend. In addition of PSF with PVDF, the peak shifts toward higher frequency side suggesting the speed up the relaxation process. AC dielectric data is also combined with thermally stimulated depolarization current (TSDC) data which is generally studied for low-frequency dielectric properties of polymers blends so as to produce the results in a wide frequency range. The glass transition temperature (T_g) of the blend was studied by differential scanning calorimetric technique (DSC), the T_g was compared and correlated with TSDC peak. The blend samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) to study the formation of blend and micro structural properties of the materials. The shifting of peak toward lower diffraction angle side confirms the reduction in particle size with increasing amorphous content in the blend.     

Synthesis,spectral and structural studies of a Mn(II) complex of [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid ethyl ester and Mn(II) and Ni(II) complexes of [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester

The new complexes [Mn(Hpchce)₂(o-phen)], {2[Mn(pchcm)(o-phen)₂]}·7H₂O and [Ni(Hpchcm)(o-phen)₂]Cl·CH₃OH with [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid ethyl ester (H₂pchce) and [N′-(pyridine-4-carbonyl)-hydrazine]-carbodithioic acid methyl ester (H₂pchcm) have been synthesized, containing o-phenanthroline (o-phen) as a coligand. These ligands and their complexes have been characterized by elemental analyses, IR, magnetic susceptibility and single crystal X-ray data. H₂pchce (2), [Mn(Hpchce)₂(o-phen)] (3) {2[Mn(pchcm)(o-phen)₂]}·7H₂O (4) and [Ni(Hpchcm)(o-phen)₂]Cl·CH₃OH (5) crystallized in the monoclinic system, space group Pc, C2/c, P21/n and P21/n, respectively. The (N, O) donor sites of the bidentate ligands chelate the Mn(II) and Ni(II) centers forming a five-membered CN₂OM ring. The resulting complexes are paramagnetic and have a distorted octahedral geometry.     

Unsymmetrically substituted 9,10-dihydro-9,10-diboraanthracenes as versatile building blocks for boron-doped π-conjugated systems

The targeted hydrolysis of the 9,10-dihydro-9,10-diboraanthracene adduct (Me(2)S)HB(C(6)H(4))(2)BH(SMe(2)) (1) with 0.5 equiv of H(2)O leads to formation of the borinic acid anhydride [(Me(2)S)HB(C(6)H(4))(2)B](2)O (2) and thereby provides access to the field of unsymmetrically substituted 9,10-dihydro-9,10-diboraanthracenes. Compound 2 reacts with tBuC≡CH to give the corresponding vinyl derivative in an essentially quantitative conversion. Subsequent cleavage of the B-O-B bridge by LiAlH(4) with formation of hydridoborate functionalities is possible but is accompanied by partial B-C(vinyl) bond degradation. This situation changes when the related mesityl derivative [MesB(C(6)H(4))(2)B](2)O (7) is employed, which can be synthesized from BrB(C(6)H(4))(2)BBr (6) by treatment with 1 equiv of MesMgBr and subsequent hydrolysis. The reaction of 7 with LiAlH(4) in tetrahydrofuran (THF) furnishes Li[MesB(C(6)H(4))(2)BH(2)] (8); hydride elimination with Me(3)SiCl leads to formation of the THF adduct MesB(C(6)H(4))(2)BH(THF) (9·THF). Alternatively, 7 can be transformed into the bromoborane MesB(C(6)H(4))(2)BBr (10) by treatment with BBr(3). A Br/H-exchange reaction between 10 and Et(3)SiH yields the donor-free borane MesB(C(6)H(4))(2)BH (9), which forms B-H-B bridged dimers (9)(2) in the solid state. The vinyl borane MesB(C(6)H(4))(2)BC(H)=C(H)Mes (14) is accessible from MesC≡CH and either 9·THF or 9. Compared with the related compound Mes(2)BC(H)=C(H)Mes, the electronic absorption and emission spectra of 14 reveal bathochromic shifts of Δλ(abs)=17 nm and Δλ(em)=74 nm, which can be attributed to the rigid, fully delocalized π framework of the [MesB(C(6)H(4))(2)B] chromophore.     

Gold-catalysed synthesis of amino acid-derived 2,5-disubstituted oxazoles

Amino acid-derived propargylic amides are cyclised in a one-pot, Au(III)-catalysed operation to yield 5-bromomethyl oxazoles. These compounds are further elaborated to bis-heterocycles, dipeptide mimics and more.