Photoassisted "gate-lock" fluorescence "turn-on" in a new Schiff base and coordination ability of E-Z isomers

Rapid photoresponse (1.0-8.0 min) through fluorescence "turn-on" signaling displayed by a novel Schiff base (L) creating "gate lock" via intramolecular C-H···N interaction in photoisomerized product (L') has been described. Coordination chemistry of pre- and postirradiated species demonstrated a drastic change in the reactivity which has been supported by NMR, HRMS, UV-vis, emission, electrochemical, and complexation studies.     

A catalyst free convenient one-pot synthesis of multisubstituted chromeno-thiazolones

Herein, we report a simple, convenient and catalyst free one-pot synthesis of chromenothiazolone analogues via multicomponent reaction between thiazolidine-2,4-dione, aromatic aldehyde and phenol. This reaction proceeded smoothly in good to excellent yields and offered several other advantages including short reaction time, simple experimental workup procedure and no byproduct.     

Theoretical investigation of the electrochemical mechanism of water splitting on a titanium oxide cluster model

The step-by-step electrochemical mechanism of water splitting by removal of protons and electrons is examined for the reaction of one and two water molecules on a Ti(2)O(4) cluster. Density functional theory (B3LYP) and coupled cluster single point calculations are employed to compute gas phase reaction energies. The polarizable continuum model (PCM) is utilized to calculate energies in the aqueous phase. Both neutral and alkaline media are considered. Proton and electron removal steps are generally found to be highly endothermic, with the exception of proton removal steps in alkaline medium. The effect of an external potential on reaction energies is considered. Oxygen-oxygen bonds form after the removal of only two electrons.     

Convenient Route to Alkylene Dithiophosphato Ligands: Synthesis and Crystallographic Analysis of [OCH<Subscript>2</Subscript>CMe<Subscript>2</Subscript>CH<Subscript>2</Subscript>OPS<Subscript>2</Subscript>HNEt<Subscript>3</Subscript>]

Abstract  

Triethylammonium salts of O,O′-alkylene dithiophosphato like OGOPS₂HNEt₃, [where, G = –CH₂CMe₂CH₂–(1), –CH₂CEt₂CH₂–(2), –CMe₂CH₂CHMe–(3) and –CMe₂CMe₂–(4)] have been synthesized in quantitative yield by the direct reaction of P₂S₅ with 1,2- and 1,3-substituted glycols in presence of triethylamine, Et₃N, in 1:2:2 molar stoichiometry in toluene. These have been mainly characterized by molecular weight, IR and NMR (¹H, ¹³C and ³¹P) spectroscopic studies. Single crystal X-ray structure analysis of [OCH₂CMe₂CH₂OPS₂HNEt₃] reveals that phosphorus atom is tetrahedrally bonded to two sulfur atoms and two oxygen atoms in the ring and the molecule exists as discrete cation and anion. The structure is stabilized by cation–anion N–H···S hydrogen bonded interactions. Antiparallel pattern of triethylammonium ion is sandwiched within the two-dimensional layers of the ring system.     

A multifractal detrended fluctuation analysis (MDFA) of the Chinese growth enterprise market (GEM)

A multifractal, detrended fluctuation approach is used to analyze the growth enterprise market (GEM) in China involving a range of correlations in fluctuations of share prices (fat tail), persistent and anti-persistent states. Our analysis exhibits company-specific multifractal characteristics, which vary among the companies listed in the same industry, e.g., the power-law cross-correlations between computer and electronics sectors. These results may help reduce the risk in complex financial markets.     

Tetraethylorthosilicate film modified with protein to fabricate cholesterol biosensor

Sol-gel derived tetraethylorthosilicate (TEOS) films were prepared by spin coating method on indium tin oxide (ITO) coated glass plate. Hydrophobic interaction method was used to coat the bovine serum albumin film over the surface of tetraethylorthosilicate sol-gel film to minimize cracking, biofouling and to improve the stability of the film. Cholesterol oxidase (ChOx) and horseradish peroxidase (HRP) were immobilized using covalent linkage with bovine albumin serum film to enhance the loading of the enzyme to improve the sensitivity of biosensor. Further ITO-TEOS-BSA-ChOx/HRP film was characterized by UV-vis, FTIR and SEM techniques. The optical response of the ITO-TEOS-BSA-ChOx/HRP biosensor was found to be linear in the range of 2-8 mM for cholesterol concentration with response time approximately 20 s. Amperometric response of ITO-TEOS-BSA-ChOx/HRP was observed to be linear in the range of 2-12 mM of cholesterol concentration with 10-s response time. Michaelis-Menten constant was calculated 21.2 mM .The shelf life of ITO-TEOS-BSA-ChOx/HRP biosensor was approximately about 8 weeks in desiccated conditions at room temperature.     

Structural and electronic properties of neutral and ionic Ga(n)On clusters with n = 4-7

We report the results of a theoretical study of neutral, anionic, and cationic Ga(n)On clusters (n = 4-7), focusing on their ground-state configurations, stability, and electronic properties. The structural motif of these small gallium oxide clusters appears to be a rhombus or a hexagonal ring with alternate gallium and oxygen atoms. With the increase in the cluster size from Ga4O4 to Ga7O7, the ground-state configurations show a transition from planar to quasi-planar to three-dimensional structure that maximizes the number of ionic metal-oxygen bonds in the cluster. The ionization-induced distortions in the ground state of the respective neutral clusters are small. However, the nature of the LUMO orbital of the neutral isomers is found to be a key factor in determining the ordering of the low-lying isomers of the corresponding anionic clusters. A sequential addition of a GaO unit to the GaO monomer initially increases the binding energy, though values of the ionization potential and the electron affinity do not show any systematic variation in these clusters.     

Bridging converts a noncytotoxic nor-paclitaxel derivative to a cytotoxic analogue by constraining it to the T-Taxol conformation

The synthesis of the bridged A-nor-paclitaxel 4 has been achieved from paclitaxel in a key test of the T-Taxol conformational hypothesis. Although the unbridged A-nor-paclitaxel 3 is essentially noncytotoxic, the bridged analogue 4 is strongly cytotoxic. This result provides strong evidence for the T-Taxol conformation as the bioactive tubulin-binding conformation of paclitaxel.     

Design and surface modification of potential luminomagnetic nanocarriers for biomedical applications

Targeted delivery of therapeutics possesses the potential to localize therapeutic agents to a specific tissue as a mechanism to enhance treatment efficacy and mitigate side effects. Moeities that combine imaging and therapeutic modalities in a single macromolecular construct may confer advantages in the development and applications of nanomedicine. Here is an insight into the synthesis of luminomagnetic (luminescent and magnetic, simultaneously) nanocarriers of ZnO:Fe, synthesized by a simple co-precipitation method and surface modified by the ligand folate. This functionalized luminomagnetic nanocarrier system is a bioconjugation approach which combines the specificity of folate receptors on cancer cells with the excellent optical and magnetic properties of the nanoparticles so as to develop biocompatible molecular imaging agents, drug delivery systems, and hyperthermia agents. The vibrating sample magnetometer (VSM) studies showed clear hysteresis loops having coercivity 5.1 mT with corresponding magnetization of remanence 7.6 × 10⁻³ emu/g, indicating strong magnetic character of the samples. X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements show that these nanoparticles are spherical with 6–9 nm size and hence are quite appropriate for in vivo applications as well. The immobilization of folic acid was confirmed by fourier transform infrared (FTIR) analysis. All these properties make these luminomagnetic nanocarriers one of the most feasible candidates for folate receptor-mediated biomedical applications.     

Formation of ZnO@Cd(OH)2 core-shell nanoparticles by sol-gel method: An approach to modify surface chemistry for stable and enhanced green emission

We report the formation of highly stable and luminescent ZnO@Cd(OH)₂ core-shell nanoparticles by simple introduction of cadmium salt in the initial precursor solution, used to synthesize ZnO nanoparticles by sol-gel route. The cadmium to zinc salt concentration ratio has been also varied to control the growth of ZnO nanoparticles at the smaller particle size. Formation of ZnO@Cd(OH)₂ core-shell nanostructure has been confirmed by X-ray diffraction (XRD), energy dispersive analysis of X-rays (EDAX) and X-ray photoelectron spectroscopy (XPS). UV-vis absorption spectroscopy exhibits blue-shift in absorption edge on increasing cadmium concentrations. The photoluminescence emission spectra showed the remarkably stable and enhanced visible (green) emission from suspended ZnO@Cd(OH)₂ nanoparticles in comparison to bare ZnO nanoparticles. It is postulated that Cd(OH)₂ layer at the surface of ZnO nanoparticles prevents the agglomeration of nanoparticles and efficiently assists the trapping of hole at the surface site, a first step necessary for visible emission. The Fourier transform infrared spectroscopy (FTIR) also supports our assumption about surface chemistry.