Synthesis,spectroscopic, structural and thermal characterizations of [(C7H6NO4)2TeBr6·4H2O]

Tellurium (IV) complexes with pyridine-2,6-dicarboxylate ligand were synthesized by slow evaporation from aqueous solutions yielding a new compound: [(C₇H₆NO₄)₂TeBr₆·4H₂O]. The structure of this compound was solved and refined by single-crystal X-ray diffraction. The compound is centrosymmetric P2₁/c (N°: 14) with the parameters a = 8.875(5) Å, b = 15.174(5) Å, c = 10.199(5) Å, β = 94.271° (5) and Z = 2. The structure consists of isolated H₂O, isolated [TeBr₆]^2? octahedral anions and (pyridine-2,6-dicarboxylate) [C₇H₆NO₄]⁺ cations. The stability of the structure was ensured by ionic and hydrogen bonding contacts (N–H?Br and O–H?Br) and Van-Der Walls interaction. The thermal decomposition of the compound was studied by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The FTIR and Raman spectroscopy at different temperatures confirm the existence of vibrational modes that correspond to the organic, inorganic and water molecular groups. Additionally, the UV–Vis diffuse reflectance spectrum was recorded in order to investigate the band gap nature. The measurements show that this compound exhibits a semiconducting behavior with an optical band gap of 2.66 eV.     

Organocatalytic chemoselective monoacylation of 1,n-linear disulfonamides

Predominant monoacylation of 1,n-linear disulfonamides took place in the presence of pyrrolidinopyridine-type organocatalysts when the chain length of the linear disulfonamides was n = 3, 4, or 5 (monoacylate/diacylate = up to 44). The chemoselectivity of the competitive acylation between N,N′-ditosyl-1,5-pentanediamine (n = 5) and N,N′-ditosyl-1,3-propanediamine (n = 3) was found to be 36, favoring the former substrate. Different chain length by only one carbon atom was discriminated in the competitive acylation between N,N′-ditosyl-1,5-pentanediamine (n = 5) and of N,N′-ditosyl-1,4-butanediamine (n = 4) with the relative acylation rate of 16 in the presence of the organocatalyst.     

Synthesis of a reduction-sensitive Bletilla striata polysaccharide amphiphilic copolymer

A reduction-sensitive stearic acid modified-Bletilla striata polysaccharide amphiphilic copolymer is synthesized. The copolymer enabled to spontaneously form micelles which display faster docetaxel release rates under reduction condition and enhanced anticancer activity in vitro after incorporating docetaxel into micelles.     

Novel dual inhibitors against FP-2 and PfDHFR as potential antimalarial agents: Design,synthesis and biological evaluation

A series of novel 2,4-diaminopyrimidine-modified compounds was designed and synthesized. Compound 14 showed micromolar dual inhibitory effect on both FP-2 and PfDHFR, and potential inhibition to the proliferation of P. falciparum 3D7 strain and chloroquine-resistant P. falciparum Dd2 strain.     

A nitroxide diradical containing a ferrocen-1,1′-diyl-substituted 1,3-diazetidine-2,4-diimine coupler

An Aza-Wittig reaction of 1,1′-bis(triphenylphosphoranylidenamino)-ferrocene with 3-isocyanato-2,2,5,5-tetramethyl-2,5-dihydro-1H-pyrrol-1-oxyl and subsequent intramolecular [2+2]-cycloaddition of the bis(carbodiimide) intermediate was used for the synthesis of a 1,3-diazetidine-2,4-diimine moiety bearing two radical groups and bridging the cyclopentadienyl (Cp) rings. According to single-crystal X-ray data, the planar 2,4-diimino-1,3-diazetidine moiety adopts a perpendicular orientation with respect to the eclipsed Cp rings. One of the radical groups lies almost within the plane of the four-membered 1,3-diazetidine ring, while the other has a conformationally preferred orientation with dihedral angles ±62.3°. The two Cp rings are constricted by the 1,3-diazetidine-2,4-diimine moiety so that the angle between their planes is 11.0°. The synthesized diradical contains ferrocene and nitroxide redox signaling units that can be oxidized step-by-step at E_1/2 = 0.26 and 0.48 V (vs Fc/Fc⁺), respectively. Electron spin resonance spectroscopy revealed a moderate exchange interaction (|J| ～ a_N) between the two nitroxide radical moieties and the following values of zero-field splitting parameters: ∣D∣ = 3.5 mT and E/D = 0 were obtained. These data were in agreement with density functional theory calculations. The newly developed approach to multispin systems may be interesting for the construction of weakly coupled rigid polyradicals for quantum technologies, the molecular design of magnets, and the creation of ferrocene-based electron-paramagnetic-resonance–active chemical sensors.     

Improved activity of SnO for the photocatalytic oxygen evolution

SnO prepared by soft chemistry exhibits a black color and semiconducting properties. The X-ray diffraction indicates a tetragonal symmetry (SG: P4/nmm) with nano crystallites of an average size of 85 nm. The forbidden band, determined from the diffuse reflectance is found to be 1.46 eV. The electrical conductivity occurs by polaron hopping and follows an Arrhenius type law with activation energy of 0.21 eV, the change in the slope at 526 K is attributed to the oxidation to SnO₂. The photo-electrochemical study shows n type conduction with a flat band potential of ?0.45 V, close to the photocurrent onset potential (?0.40 V). The electrochemical impedance spectroscopy shows the bulk contribution of SnO (R_b = 1.7 kΩ cm²) and decreases down to 1.89 kΩ cm² under illumination. The photocatalytic properties have been evaluated for the first time for to the oxygen evolution. The valence band, deriving from Sn²⁺: 5p orbital with a potential (?0.80 V_SCE/5.55 eV), is suitably positioned with respect to O₂/H₂O level (～0.6 V_SCE), leading to water oxidation under visible light. The best performance occurs at pH ～ 7 with an oxygen liberation rate of 23 µmol mL h^?1 (mg catalyst)^?1 and a quantum efficiency of 1.2%. An improvement of ～13% is observed on the system SnO/clay.     

One-pot photoreduction to prepare NIR-absorbing plasmonic gold nanoparticles tethered by amphiphilic polypeptide copolymer for synergistic photothermal-chemotherapy

We developed one-pot photoreduction strategy to fabricate the NIR-absorbing plasmonic PLC-b-PEO@Au NPs. It possessed strong NIR absorption at 700-1100 nm, an ultrahigh photothermal conversion efficiency of 62.1%, and good photostability.     

Poly(m-ferrocenylaniline) modified carbon nanotubes-paste electrode encapsulated in nafion film for selective and sensitive determination of dopamine and uric acid in the presence of ascorbic acid

A nafion covered carbon nanotubes-paste electrode modified with poly(m-ferrocenylaniline), (Nf/p(FcAni)-CNTsPE), provides a novel voltammetric sensor for the selective determination of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). We studied the electrochemical activity of Nf/p(FcAni)-CNTsPE toward DA, UA, and AA by differential pulse voltammetry (DPV). DA and UA anodic peaks appear at 0.30 and 0.45 V, respectively while an anodic peak for AA was not observed. DPV oxidation peak values are linearly dependent on DA concentration over the range 1–150 μM (r² = 0.992), and on UA concentration over the range 5–250 μM (r² = 0.997). DA and UA detection limits are estimated to be 0.21 and 0.58 μM, respectively. The modified electrode shows both good selectivity and reproducibility for the selective determination of DA and UA in real samples. Finally, the modified electrode was successfully applied for the determination of DA and UA in pharmaceutical or biological sample fluids.     

Anionic polymerization initiated by lithium amides for preparing high molecular weight polyacrylonitrile

Lithium amides have been proved to be effective anionic initiators for the anionic polymerization of acrylonitrile to get high molecular weight polyacrylonitrile in this study. Polyacrylonitrile with weightaverage molecular weight ranging from 1.02 × 10~6 g/mol to 1.23 ×10~6 g/mol (M_w/M_n= 1.9-2.2) could be prepared utilizing lithium amides derived from diisopropylamine, diethylamine, hexamethyldisilazane,dicyclohexylamine, and 2,2,6,6-tetramethylpiperidine as initiators. The polymerization of acrylonitrile proceeded in a homogeneous manner in N,N-di methyl for mamide and insignificant contribution of side reactions was confirmed.     

In-line Raman spectroscopy and advanced process control for the extraction of anethole and fenchone from fennel (Foeniculum vulgare L. MILL.)

Plants are a desirable source for molecules of all kinds and for every purpose. Besides traditional techniques for extraction, plants are challenging for modern process engineering due to great variations because of their natural origin. One way to ensure high quality and low costs, as well as highly resource-efficient extraction, is in-line monitoring and process control. This study demonstrates the use of in-line Raman spectroscopy for monitoring the extraction of anethole and fenchone from fennel seed as a typical example. A partial least square calibration model with high accuracy was created. (Anethole: R² = 0.99, root mean square error of calibration (RMSEC) = 0.01256 g/L, root mean square error of validation (RMSEV) = 0.02608 g/L, and calibration range up to 2 g/L. Fenchone: R² = 0.98, RMSEC = 0.01188 g/L, RMSEV = 0.01945 g/L, and calibration up to 0.75 g/L.) These data are directly linked to a physicochemical process model to control the extraction process in real time and to perform predictive simulations while processing. The added value of this approach for modern phytoextraction is highlighted and exemplified as a major step toward sustainable Green Extraction processes.     

Diterpenoids from the aerial parts of Leonurus macranthus

One cis clerodane-type (1) and three highly oxygenated labdane-type diterpenes (2-4) were isolated from the aerial parts of Leonurus macranthus. Compound 1 represents the first example of cis clerodane-type diterpene in the plants of Leonurus genus.     

Line tension and its influence on droplets and particles at surfaces

In this review we examine the influence of the line tension τ on droplets and particles at surfaces. The line tension influences the nucleation behavior and contact angle of liquid droplets at both liquid and solid surfaces and alters the attachment energetics of solid particles to liquid surfaces. Many factors, occurring over a wide range of length scales, contribute to the line tension. On atomic scales, atomic rearrangements and reorientations of submolecular components give rise to an atomic line tension contribution τ_atom (～1 nN), which depends on the similarity/dissimilarity of the droplet/particle surface composition compared with the surface upon which it resides. At nanometer length scales, an integration over the van der Waals interfacial potential gives rise to a mesoscale contribution |τ_vdW| ～ 1–100 pN while, at millimeter length scales, the gravitational potential provides a gravitational contribution τ_grav ～ +1–10 μN. τ_grav is always positive, whereas, τ_vdW can have either sign. Near wetting, for very small contact angle droplets, a negative line tension may give rise to a contact line instability. We examine these and other issues in this review.     

Modular construction of pyrido[24]crown-8-based templates in the self-assembly of cross-linked [n]catenanes

Starting from the versatile 4-bromopyrido[24]crown-8 building block, novel ditopic and tritopic receptors have been synthesized and shown to be appropriate hosts for bis(4-formylbenzyl)ammonium hexafluorophosphate. Association constants (per binding site) for the corresponding [3]- and [4]pseudorotaxanes, assembled from these components, were determined to be 2753  M^?1 and 723  M^?1, respectively. Mechanical bond formation was attempted utilizing dynamic imine bond formation between the formyl groups of the bound dibenzylammonium threads and p-phenylenediamine.     

Using enantioselective dispersive liquid–liquid microextraction for the microseparation of trans-cyclohexane-1,2-diamine enantiomers

A new chiral separation system effective for the enantioselective extraction of racemic trans-cyclohexane-1,2-diamine is presented. Enantioselective dispersive liquid–liquid microextraction has been used for the chiral microseparation of trans-cyclohexane-1,2-diamine, with a chiral azophenolic crown ether being identified as a versatile chiral selector. The influence of various process conditions on the extraction performance was studied experimentally. It was found that the operational selectivity in one extraction step is mainly related to the type and volume of the solvents, chiral selector concentration, extraction time, temperature of sample solution, and pH. At optimum conditions (300 μL of diethyl ether as the extraction solvent 1 mL of methanol as the disperser solvent, with 5 mmol L^?1 chiral selector concentration, pH of the sample equal to 4.5, 30 min extraction time and a temperature of 10 °C), the distribution ratio of (R,R)- and (S,S)-trans-cyclohexane-1,2-diamine was 18.3 and 1.8, respectively, while the enantioselectivity value of 10.2 was found at the optimum condition.     

N-Heterocyclic carbene-catalyzed [4 + 2] cyclization of α-chloroaldehydes and aurones: Highly enantioselective synthesis of benzofuran-fused dihydropyran-2-ones

The chiral N-heterocyclic carbene-catalyzed [4 + 2] annulation of α-chloroaldehydes and aurones was developed, giving the corresponding benzofuran–fused dihydropyranones in good to high yields with good cis-selectivities and excellent enantioselectivities. The catalytic cycle features with the generation of enolate from chloroaldehdye and its following [4 + 2] cycloaddtion with aurones.     

Systematic trends in (0 0 1) surface ab initio calculations of ABO3 perovskites

By means of the hybrid exchange–correlation functionals, as it is implemented in the CRYSTAL computer code, ab initio calculations for main ABO₃ perovskite (0 0 1) surfaces, namely SrTiO₃, BaTiO₃, PbTiO₃, CaTiO₃, SrZrO₃, BaZrO₃, PbZrO₃ and CaZrO₃, were performed. For ABO₃ perovskite (0 0 1) surfaces, with a few exceptions, all atoms of the upper surface layer relax inward, all atoms of the second surface layer relax outward, and all third layer atoms, again, inward. The relaxation of (0 0 1) surface metal atoms for ABO₃ perovskite upper two surface layers for both AO and BO₂-terminations, in most cases, are considerably larger than that of oxygen atoms, what leads to a considerable rumpling of the outermost plane. The ABO₃ perovskite (0 0 1) surface energies always are smaller than the (0 1 1) and especially (1 1 1) surface energies. The ABO₃ perovskite AO and BO₂-terminated (0 0 1) surface band gaps always are reduced with respect to the bulk values. The B–O chemical bond population in ABO₃ perovskite bulk always are smaller than near the (0 0 1) and especially (0 1 1) surfaces.     

Chloro/bromotrimethylsilane-Cu(NO3)2·3H2O: Safe and efficient reagent system for the decarboxylative ipso-nitration and dibromination of cinnamic acids

Further synthetic potential of halotrimethylsilane-nitrate salt mixture is revealed. A mixture of TMSX-Cu(NO₃)₂·3H₂O system is found to be an efficient reagent system for both the decarboxylative nitration (ipso-nitration) when X = Cl, and dibromination of cinnamic acids, with X = Br, under mild conditions. The reactions are safe and simple, affording the corresponding products (E)-β-nitrostyrenes, and anti-2,3-dibromo-3-phenylpropanoic acids in high yields with high selectivity in a relatively short time. Use of hazardous and toxic nitrating systems such as acetyl nitrate and brominating agents such as molecular bromine can be avoided.     

Synthesis and red electroluminescence of a dimesityl-functionalized bistetracene

The single crystal analysis of the as-prepared 8,16-dimesityltetraceno[2,1,12,11-opqra]tetracene (DMTA) suggests that the parent bistetracene backbone is almost in a plane without any intermolecular p-stacking interaction. The fabricated devices based on DMTA as an emitter exhibit a maximum brightness of 632 cd/m² at 14.7 V with the CIE coordinate of (0.623, 0.349).     

Enantioselective enzymatic resolution of racemic alcohols by lipases in green organic solvents

The effects of two eco-friendly solvents, 2-methyltetrahydrofuran (MeTHF) and cyclopentyl methyl ether (CPME), on the enzyme activity and enantioselectivity of Novozym 435, Candida rugosa lipase (CRL), Porcine pancreas lipase (PPL), Lipase AK, Lipase PS, and Lipozyme, a series of commercial lipases, in the enantioselective transesterfications of racemic menthol, racemic sulcatol and racemic α-cyclogeraniol were studied. Vinyl acetate was chosen as the acyl donor and the reactions were carried out at water activity 0.06. The activity of lipases in CPME was similar to that observed in other largely employed organic solvents [toluene and tert-butyl methyl ether (MTBE)], and was slightly lower in MeTHF. However, for most of the lipases tested, the enantioselectivity was higher in the eco-friendly solvents. Lipase AK exhibited a high enantioselectivity (E = 232) for the resolution of racemic menthol but the reaction rate was low. Lipase formulation (the enzyme was frozen and lyophilized in potassium phosphate buffer without and with 5% (w/v) of sucrose, d-mannitol, or methoxy poly(ethylene glycol)) was tested with this lipase in order to improve its activity, which increased up to 4.5 times, compared to the untreated enzyme. CALB was found to be a useful biocatalyst for the resolution of racemic sulcatol, where high activity and enantioselectivity were obtained (E ≥ 1000). For the resolution of the racemic primary alcohol α-cyclogeraniol, most of the lipases tested were active but not enantioselective, except lipase PS which displayed a moderate enantioselectivity (E = 19). The effect of the presence of a low percentage of two ionic liquids (ILs) 1-Butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMIM][TFSI]) (5% (v/v)) and 1-Butyl-3-methylimidazoliumtetrafluoroborate ([BMIM][BF4]) (1% (v/v)) in the medium was also investigated. Only in the case of CRL the ILs slightly increased the enantioselectivity from E = 91 to E = 103 and E = 120 for [BMIM][TFSI] and [BMIM][BF4], respectively. However, in all cases ILs caused a decrease of enzyme activity.     

Synthesis,characterization and anti-bacterial activity of divalent transition metal complexes of hydrazine and trimesic acid

Transition metal complexes of trimesic acid and hydrazine mixed-ligands with a general formula M(Htma)(N₂H₄)₂, where, M = Mn, Co, Ni, Cu and Zn; H₃tma = trimesic acid, have been prepared and characterized by elemental, structural, spectral and thermal analyses. For the complexes, the carboxylate ν_asym and ν_sym stretchings are observed at about 1626 and 1367 cm^?1 respectively, with Δν between them of ～260 cm^?1, showing the unidentate coordination of each carboxylate group. The hydrazine moieties are present as bridging bidentates. Electronic and EPR spectral studies suggest an octahedral geometry for the complexes. All these complexes show three steps of decomposition in TGA/DTA. SEM images of CuO and MnO residues obtained from the complexes show nano-sized clusters suggesting that the complexes may be used as precursors for nano-CuO and nano-MnO preparation. The antimicrobial activities of the prepared complexes, against four bacteria have been evaluated.