A mechanistic approach to photochemical behavior of 4‐anisyl‐4‐methyl‐2,6‐diphenyl‐4H‐thiopyran‐1,1‐dioxide

Photoisomerization of 4‐anisyl‐4‐methyl‐2,6‐diphenyl‐4H‐thiopyran‐1,1‐dioxide is described in the presence of a sensitizer and new mechanistic features are proposed. The relative molar ratios of the stereoselective photoproducts compared in the presence and the absence of sensitizer in different concentrations of the starting material using hplc. The results observed are discussed on the basis of a triplet excited state thiadi‐π‐methane rearrangement.     

Effect of finite-temperature local field corrections on many-body properties of quantum wires

The effect of low temperature on the many-body properties of an n-type GaAs-based quasi one-dimensional electron gas (quantum wire) has been investigated in the RPA, Hubbard and STLS approximations. Numerical results for the finite-temperature static structure factors, local field corrections, pair correlation functions, plasmon dispersion relations and inverse static dielectric functions of the system have been obtained and compared with the zero-temperature values. As a general result, the behavior of the system at finite-temperature does not change significantly at small values of wave vectors. Also, it has been found out that while applying the temperature dependent Hubbard and STLS to the quantum wire yields different results for local field corrections and pair correlation functions, the increase in temperature within all approximations causes the plasmon modes to shift upward in energy and the sharp peaks in the inverse static dielectric curve to become less pronounced.     

Organosulfur phosphonium salt-mediated synthesis of functionalized thiopyran derivatives

Methyl 4-oxotetrahydro-2H-thiopyran-3-carboxylate as a CH-acid undergoes a mild reaction with acetylenic esters in the presence of triphenylphosphine to produce phosphorus ylides possessing thiopyran-4-one ring moiety. The resulted phosphorus ylides when heated in toluene afforded functionalized thiopyran derivatives through intramolecular Wittig reaction.     

RQAR: Location-free reliable and QoS-aware routing protocol for mobile sink underwater wireless sensor networks

Underwater Wireless Sensor Networks (UWSNs) have attracted attention from academics and industries due to many applications such as pollution monitoring, military, tsunami warning, and underwater exploration. One of the effective factors in these applications is efficient communication between underwater sensors. But this process is very challenging in UWSNs due to special conditions and underwater harsh environments. Therefore, designing routing protocols for efficient communication between sensors and sink is an important issue in UWSNs. In this context, this paper proposed a location-free Reliable and QoS-Aware Routing (RQAR) protocol for mobile sink UWSNs. RQAR designed using Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and does not require the position information of the sensor nodes, which is cumbersome and difficult to obtain. Proposed protocol considers multiple parameters including link quality, hop count, congestion, and residual energy for qos support, and reliable data delivery RQAR also minimizes the effects of hole occurrence by increasing the transmission range as much as possible and ensures communication stability. The simulation results using NS2 showed the superiority of RQAR in improving end-to-end delay, packet delivery ratio, and network throughput compared to the previous methods.     

Potentiometric study of complexation of phenylaza-15-crown-5, 4-nitrobenzo-15-crown-5 and dibenzopyridino-18-crown-6 and other derivative of 18-crowns-6 with Na+ ion in methanol

The complexation reaction of phenylaza-15-crown-5, and 4-nitrobenzo-15-crown-5, benzo-15-crown-5 and dibenzopyrdino-18-crwon-6, dibenzo-18-crown-6,dicyclohexyl-18-crown-6(cis and trans), and 18-crown-6 with Na⁺ ion in methanol have been studied by potentiometric method. The Na⁺ ion-selective electrode has been used both as indicator and reference electrode. The stoichiometry and stability constants of complexes of these crown ethers with sodium ion were evaluated by MINIQUAD program. The major trend of stability of resulting complexes of these macrocycle with Na⁺ ion varied in the order DCY18C6 > DB18C6 > 18C6 > DBPY18C6 > phenylaza-15C5 > benzo-15C5 > 4-nitrobenzo-15C5. The obtained results in particular stability constant of complexes of DBPY18C6, phenylaza-15C5 and 4-nitrobenzo-15C5 with sodium ion in comparison with other crowns ether are novel, and interesting.     

A novel thermo-sensitive nanogel composing of poly(<Emphasis Type="Italic">N</Emphasis>-isopropylacrylamide) grafted onto alginate-modified graphene oxide for hydrophilic anticancer drug delivery

Nanogels have been demonstrated to be desirable for hydrophilic anticancer drug delivery. This study presents a novel nanogel consisting of sodium alginate-modified graphene oxide (SA-GO) and N-isopropylacrylamide (NIPAM) for sustained delivery of doxorubicin (DOX) drug. The PNIPAM/SA-GO nanogel was studied by various techniques including scanning electron microscopy, atomic force microscopy, dynamic light scattering, Fourier transform infrared spectroscopy, and thermo-gravimetric analysis. Subsequently, the thermo-responsive behavior of the PNIPAM/SA-GO nanogel was investigated by UV–Vis spectroscopy. DOX was successfully loaded into the PNIPAM/SA-GO nanogel in order to study entrapment efficiency and drug release behavior. Moreover, biocompatibility of the DOX-loaded PNIPAM/SA-GO nanogel was examined against Hella cells and was compared with free PNIPAM/SA-GO nanogel and DOX. This work offers that the nanogels could be developed further as an effective bioactive molecule delivery system.     

Preparation of Zinc (II) and cadmium (II) complexes of the tetradentate Schiff base ligand 2-((E)-(2-(2-(pyridine-2-yl)- ethylthio)ethylimino)methyl)-4-bromophenol (PytBrsalH)

We describe the synthesis and characterization of two new zinc (II) and cadmium (II) complexes of the tetradentate dissymmetric Schiff base ligand 2-((E)-(2-(2-(pyridine-2-yl)ethylthio)ethylimino)methyl)-4-bromophenol (PytBrsalH), prepared from 1-(2-pyridyl)-3-thia-5-aminopentane (pyta) and 5-bromosalicylaldehyde. The complexes were synthesized by treating an ethanolic solution of the ligand with equimolar amounts of appropriate metal salts in 1 M methanolic solution of NaOH or alternatively, by a more direct route in which the two reactants are added to a solution of the ligand immediately after formation of the latter and prior to any isolation. The complexes were characterized by elemental analysis, FTIR, (1)H-NMR, electronic spectra and molar conductivity. According to obtained data, the probable coordination geometries of zinc and cadmium in these complexes with mixed N, S and O donor atoms are tetrahedral- and octahedral-like,respectively. Both complexes were found to be 1:1 electrolyte systems in acetonitrile.     

Highly luminescent lead sulfide nanocrystals in organic solvents and water through ligand exchange with poly(acrylic acid)

Hydrophobic lead sulfide quantum dots (PbS/OA) synthesized in the presence of oleic acid were transferred from nonpolar organic solvents to polar solvents such as alcohols and water by a simple ligand exchange with poly(acrylic acid) (PAA). Ligand exchange took place rapidly at room temperature When a colloidal solution of PbS/OA in tetrahydrofuran (THF) was treated with excess PAA, the PbS/PAA nanocrystals that formed were insoluble in hexane and toluene but could be dissolved in methanol or water, where they formed colloidal solutions that were stable for months. Ligand exchange was accompanied by a small blue shift in the band-edge absorption, consistent with a small reduction in particle size. While there was a decrease in quantum yield associated with ligand exchange and transfer to polar solvents, as is commonly found for colloidal quantum dots, the quantum yields determined were impressively high: PbS/OA in toluene (82%) and in THF (58%); PbS/PAA in THF (42%) and in water (24%). The quantum yields for the PbS/PAA solutions decreased over time as the solutions were allowed to age in the presence of air.