UTLC: An Advanced Technique in Planar Chromatography

As part of increasing research in the field of separation science, there have been many efforts to undertake planar chromatography with more efficient separation and better resolution in the shortest period of time, together with a specificity and a capability to identify more precisely an unknown compound present in a mixture. Ultra-thin layer chromatography (UTLC) is a modern technique which gives separation within 10–30 mm and development in just 1–6 min, with the consumption of less solvent. The stationary phase of UTLC is made up of a silica gel monolithic layer of 10 μm thickness having 3- to 4-nm mesopores and 1- to 2-μm macropores. Glancing angle deposition (GLAD)-UTLC is a modification of UTLC which gives separation within 15 mm distance and in less than 2 min. Anisotropic media of GLAD UTLC gives a unique migration direction effect. UTLC atmospheric pressure–matrix-assisted laser desorption ionizer–mass spectrometery (UTLC-AP-MALDI-MS) is a choice of technique for the identification of an unknown compound in a mixture or an impure form. ULTC-AP-MALDI-MS allows the fast changing of plates, produces more intact protonated molecules, less fragmentation and less entry of chromatographic material, and yielding less complicated spectra than the vacuum condition. Thus, UTLC is a useful technique for very rapidly giving the separation and identification of new components present in mixtures. This review provides a brief overview of UTLC, the stationary phases used for UTLC, and the detection options and applications of UTLC.     

Synthesis and Spectral Characterization of Some New 4-(2,6-Diarylpyridin-4-yl)-2H-chromen-2-ones

Some new 4-(2,6-diarylpyridin-4-yl)-2H-chromen-2-one derivatives 5a–l have been synthesized by reacting 4-(3-oxo-3-arylprop-1-enyl)-2H-chromen-2-ones 3a–c with appropriate 1-(2-oxo-2-arylethyl)pyridinium bromide salt 4a–d in the presence of ammonium acetate in refluxing glacial acetic acid. The newly synthesized compounds have been characterized by elemental and spectral analysis.     

Ion- and atom-leaching mechanisms from palladium nanoparticles in cross-coupling reactions

Leaching of palladium species from Pd nanoparticles under C--C coupling conditions was observed for both Heck and Suzuki reactions by using a special membrane reactor. The membrane allows the passage of palladium atoms and ions, but not of species larger than 5 nm. Three possible mechanistic scenarios for palladium leaching were investigated with the aim of identifying the true catalytic species. Firstly, we examined whether or not palladium(0) atoms could leach from clusters under non-oxidising conditions. By using our membrane reactor, we proved that this indeed happens. We then investigated whether or not small palladium(0) clusters could in fact be the active catalytic species by analysing the reaction composition and the palladium species that diffused through the membrane. Neither TEM nor ICP analysis supported this scenario. Finally, we tested whether or not palladium(II) ions could be leached in the presence of PhI by oxidative addition and the formation of [Pd(II)ArI] complexes. Using mass spectrometry, UV-visible spectroscopy and 13C NMR spectroscopy, we observed and monitored the formation and diffusion of these complexes, which showed that the first and the third mechanistic scenarios were both possible, and were likely to occur simultaneously. Based on these findings, we maintain that palladium nanoparticles are not the true catalysts in C--C coupling reactions. Instead, catalysis is carried out by either palladium(0) atoms or palladium(II) ions that leach into solution.     

两亲性聚氨基酸三嵌段共聚物构筑pH/溶剂可控多级纳米结构

通过开环聚合（ROP）和原子转移自由基聚合（ATRP）合成了一种pH响应性三嵌段共聚物聚乙二醇-b-聚赖氨酸-b-聚苯乙烯（PEG-b-PLL-b-PS），在水-有机溶剂混合溶液中进行组装，并采用透射电子显微镜（TEM）、原子力显微镜（AFM）和衰减全反射红外光谱法（ATR-IR）表征.该三嵌段共聚物在四氢呋喃（THF）与水的混合溶剂（V：V=1：1）中可组装成疏水性聚苯乙烯为核、亲水性聚赖氨酸和聚乙二醇分别为内壳和外壳的球状胶束.采用TEM和AFM发现该球状胶束在四氢呋喃（THF）水溶液中退火7 d后可进一步转变为纤维状结构.进一步除去THF后，可恢复至粒径略小的冻结球状胶束.另外，球状胶束的粒径随着pH的增加而增加，当pH为13时，聚赖氨酸的二级结构由无规卷曲构象过渡到α-螺旋构象，聚集体由球形结构过渡到空心囊泡.溶液经透析后可使囊泡恢复至球状胶束.     

Calorimetric and Scattering Studies on Micellization of Pluronics in Aqueous Solutions: Effect of the Size of Hydrophilic PEO End Blocks,Temperature, and Added Salt

Micellar behavior of five ethylene oxide–propylene oxide (EO–PO) triblock copolymers, called Pluronics, with similar molecular weights of middle block PPO (～2250 g/mol) and varied percentages of poly(ethylene oxide) (10%, 40%, 50%, 70%, and 80%, referred to as L81, P84, P85, F87, and F88, respectively) was examined by thermal (isothermal titration calorimetry and high-sensitivity differential scanning calorimetry), spectral (UV–vis), and dynamic light scattering (DLS) techniques. Micellization was decreased with increasing hydrophilicity of copolymer but induced in the presence of salt. Critical micelle temperatures (CMTs) of copolymers at different concentrations, with and without sodium chloride, are reported. Viscosity and DLS results reveal that highly hydrophilic copolymers (F87 and F88) did not show significant change in micelle size even at temperatures close to cloud point, whereas micelle growth and sphere-to-rod transition occurred for P84 and P85. Surface tension of solutions in water and salt also show enhanced surface activity and salt-induced micellization. The CMTs for different systems using different methods are compared.     

Synthesis of some oxazolyl ‐ pyrazolyl; 1,4‐Dihydropyridinyl‐pyrazolyl and 1,2,3,4‐tetrahydro pyrimidinyl‐pyrazolyl coumarins

Various 3‐[1‐phenyl‐4‐(2‐substituted‐5‐oxo‐oxazol‐4‐ylidenemethyl) pyrazol‐3‐yl] coumarins 4a‐f ; 3‐[1‐phenyl‐4‐(2,6‐dimethyl‐3,5‐disubstituted‐1,4‐dihydropyridin‐4‐yl) pyrazol‐3‐yl] coumarins 5a‐f and 3‐[1‐phenyl‐4‐(6‐methyl‐5‐substituted‐2‐oxo‐1,2,3,4‐tetrahydropyrimidin‐4‐yl) pyrazol‐3‐yl] coumarins 6a‐f have been synthesized utilizing Erlenmyer‐Plochl reaction, Hantzsch reaction and Biginelli reaction respectively using 3‐(1‐phenyl‐4‐formyl‐pyrazol‐3‐yl) coumarins 3a‐c as a starting material.     

Exploring energy-time entanglement using geometric phase

Using the signal and idler photons produced by parametric down-conversion, we report an experimental observation of a violation of the Bell inequality for energy and time based purely on the geometric phases of the signal and idler photons. We thus show that energy-time entanglement between the signal and idler photons can be explored by means of their geometric phases. These results may have important practical implications for quantum information science by providing an additional means by which entanglement can be manipulated.     

Study of Removal of Cationic Dye from Waste Aqua Using Chromatographic Grade Silica as Adsorbent

The adsorption of cationic dye, Basic Red 13 from aqueous solution onto silica has been studied. The time growth adsorption as a function of the amount of adsorbent, pH, initial dye concentration as well as the temperature was measured of the system. Adsorption was found to follow a first-order process. Various isotherm and thermodynamic parameters for the adsorption of dye have been calculated. Isotherms were used to identify formation of either monolayer or multilayer formation whereas thermodynamic and other parameter indicated that the dye adsorption process was physisoption as well as spontaneous and exothermic in nature.     

Synthesis and antimicrobial activity of some 7‐aryl‐5,6‐dihydro‐14‐aza[1]benzopyrano[3,4‐b]phenanthren‐8H‐ones

The title compounds, 7‐aryl‐5,6‐dihydro‐14‐aza[1]benzopyrano[3,4‐b]phenanthren‐8H‐ones 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l have been synthesized by reacting various 4‐hydroxy coumarins 1a , 1b , 1c with 2‐arylidene‐1‐tetralones 2a , 2b , 2c , 2d in the presence of ammonium acetate and acetic acid under Krohnke's reaction condition. The structures of all the synthesized compounds were supported by analytical, IR, ¹H‐NMR, and ¹³C‐NMR data. All the synthesized compounds 3a , 3b , 3c , 3d , 3e , 3f , 3g , 3h , 3i , 3j , 3k , 3l have been screened for their antibacterial activities against Escherichia coli (Gram ?ve bacteria), Bacillus subtilis (Gram +ve bacteria), and antifungal activity against Candida albicans (Fungi). J. Heterocyclic Chem., (2011).