The synthesis and spectral properties of a stimuli-responsive D-π-A charge transfer dye

A new donor-π-acceptor (D-π-A) type isophorone dye was synthesized by the condensation reaction between 2-(3,5,5-trimethylcyclohex-2-enylidene)-malononitrile and indole-3-carboxaldehyde. The chemical structure of the dye was characterized by 1H NMR, EA and MS. A novel, chromogenic, fluorescent dye based on indol as donor unit and isophorone as acceptor unit displayed marked UV-visible absorption changes and highly selective fluorescence quenching in the presence of fluoride ion. The dye also exhibited sizeable colour changes when used as a pH-induced molecular switch and as a detector for volatile organic compounds. The absorption and fluorescent intensity of the dye can be reversibly selected by protonation/deprotonation of the amine moiety via control of intramolecular charge transfer (ICT), leading to a molecular switch with "on" and "off" states.     

Effects of annealing and the addition of PEG on the PVA based hydrogel by gamma ray

Poly(vinyl alcohol) (PVA) is an interesting material with good biocompatibility, high elasticity and hydrophilic characteristics. PVA hydrogels have been formed through chemical crosslinking with aldehyde, photopolymerization and physical crosslinking with freeze-thawing. In this study, crosslinked hydrogels based on PVA, and poly(ethylene glycol) (PEG) were prepared by gamma-ray irradiation, and then annealed at 120 °C. The properties of a hydrogel such as gel fraction, swelling behavior, gel strength as a function of PEG content and annealing time were investigated. Also, the thermal behaviors were examined by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The gel fraction decreases with an increase in PEG content and decrease in annealing time. The tensile strength increases with an increase in annealing time. The thermal behaviors have shown different patterns according to the annealing time. The improved properties suggest that PVA/PEG blend hydrogel can be a good candidate for applications in the articular cartilage.     

Choline chloride based eutectic solvent for the efficient synthesis of 2-amino-4H-chromen-4-yl phosphonate derivatives via multicomponent reaction under mild conditions

Synthesis of 2-amino-4H-chromen-4-ylphosphonate derivatives has been accomplished by the one-pot three-component reaction of salicylaldehyde, malononitrile/ethylcyanoacetate and dialkyl phosphites in the presence of reusable deep eutectic solvent (DES) under mild conditions. The advantages of this method are mild reaction conditions, simple work-up procedure, use of DES as a green solvent and an economical protocol for the preparation of important biologically active phosphorus-containing compounds.     

Measurements of the mass, total width, and two-photon partial width of the eta(c) meson

Using 13.4 fb(-1) of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudoscalar charmonium in the decay eta(c)-->K(0)(S)K-/+pi(+/-). We have measured the eta(c) mass to be [2980.4+/-2.3 (stat)+/-0.6 (syst)] MeV and its full width as [27.0+/-5.8 (stat)+/-1.4 (syst)] MeV. We have determined the two-photon partial width of the eta(c) meson to be [7.6+/-0.8 (stat)+/-0.4 (syst)+/-2.3 (br)] keV, with the last uncertainty associated with the decay branching fraction.     

Study of tau decays to six pions and a neutrino

The tau decays to six-pion final states have been studied with the CLEO detector at the Cornell Electron Storage Ring. The measured branching fractions are B(tau(-)-->2pi(-)pi(+)3pi(0)nu(tau)) = (2.2+/-0.3+/-0.4)x10(-4) and B(tau(-)-->3pi(-)2pi(+)pi(0)nu(tau)) = (1.7+/-0.2+/-0.2)x10(-4). A search for substructure in these decays shows that they are saturated by intermediate states with eta or omega mesons. We present the first observation of the decay tau(-)-->2pi(-)pi(+)omega(nu)tau and the branching fraction is measured to be (1.2+/-0.2+/-0.1)x10(-4). The measured branching fractions are in good agreement with the isospin expectations but somewhat below the conserved-vector-current predictions.     

Kinetics of Dimethyl Carbonate Synthesis From Ethylene Carbonate and Methanol Using Alkali-Metal Compounds as Catalysts

Dimethyl carbonate (DMC) was synthesized by the ester exchange reaction of ethylene carbonate and methanol. K₂ CO₃ , KOH, LiOH and NaOH were used as catalysts for DMC synthesis and their catalytic abilities were compared in terms of kinetics. LiOH showed the best reaction rate among the catalysts. The rate constant was estimated to be 0.02538 (dm 3 /mol) 0.21 /min at 298 K.     

Chromene and Imidazole Based D-π-A Chemosensor Preparation and Its Anion Responsive Effects

We have designed and synthesized the colorimetric chemosensor through the reactions of 2-(4H-chromen-4-yildene)malonitrile and 4-imidazolecarboxaldehyde. Due to its well conjugated D-π-A system and the existence of NH- fragment in structure, we expected that the chemosensor can detect anion using NH- fragment in the imidazole moiety of the structure. In this regard, UV-Vis absorption spectra were measured to investigate sensing properties of the probe toward different anions in DMSO. This chemosensor can detect both fluoride and cyanide ion with absorption change in intensity. In addition, pH sensing property was also investigated upon the addition of hydroxide ion. These properties are related to the deprotonation effect. The ICT system in this molecule was also observed by the computational approach using Material Studio 4.3 package.     

Characteristics of Guajazulene Based Chemosensor Toward CN− and F− Anions

A chemosensor having electron pushing donor and pulling acceptor material based on conjugation bridges, namely D-π-A structural chemosensor, was herein designed and synthesized. This chemosensor 3 contained guajazulene and indole moieties, which was synthesized through a one-step condensation reaction. The synthesized material showed very selective sensing properties towards anions. Upon the addition of CN- and F-, the remarkable changes in absorption spectra were monitored. However, each of others did not show any noticeable optical changes. The original intramolecular charge transfer system of chemosensor 3 was altered by the formation of N- at iindole moiety with anion reaction: caused by the deprotonation of NH at the indole moiety of chemosensor. With intermolecular charge transfer system between chemosensor 3 and anions, the electron density and distribution were determined by frontier calculation method.