Buncha Pulpoka

Azocalix[4]arene Strapped Calix[4]pyrrole: A Confirmable Fluoride Sensor

A new chromogenic fluoride sensor based on 1,3-di-p-nitrophenylazocalix[4]arene-calix[4]pyrrole (1) was designed and synthesized. The color of the solution of probe 1 changed upon the addition of any F(-), CH(3)CO(2)(-), PhCO(2)(-), and H(2)PO(4)(-) ions. However, from these ions the highly specific sensing of F(-) is achieved by the addition of Ca(2+) which leads to a color change from light sky blue (of 1·F(-)) back to the original light orange color of 1.

A reversible Em-FRET rhodamine-based chemosensor for carboxylate anions using a ditopic receptor strategy

A reversible rhodamine-based sensor (L1) capable of undergoing excimer-fluorescent resonance energy transfer (Em-FRET) was designed and synthesized using a ditopic receptor strategy. Addition of Cu2+ ions to a solution of L1 induced a ring-open conformation of spirolactam (Em-FRET ON), whilst ring closure was induced upon addition of CH3COO− (Em-FRET OFF).

Hybrid organic–inorganic nanomaterial sensors for selective detection of Au3+ using rhodamine-based modified polyacrylic acid (PAA)-coated FeNPs

Rhodamine derivatives were grafted on poly(acrylic acid) or PAA to obtain hydrophobically modified PAA (PAA-Rho1–4) bearing rhodamine moieties. Polymeric sensors were simply prepared by amidation reactions between PAA and rhodamine of various mole ratios to obtain PAA-Rho1, PAA-Rho2, PAA-Rho3 and PAA-Rho4 in 83%, 82%, 75% and 81% yields, respectively. Chemical compositions of PAA-Rho1–4 were studied by IR and 1H NMR spectroscopy. Chemical structures and purity of polymeric sensors were characterized by TGA, NMR, TEM and IR. It was found that polymeric sensors exhibited high selectivity and sensitivity in colorimetric and fluorescence responses toward Au3+ over other metal ions. The polymeric sensors were non-fluorescent in the spirolactam form and could be selectively converted into the fluorescent ring-opened amide form in the presence of Au3+ ions that lead to fluorescence enhancements and colorimetric changes. DFT calculation results suggested that the polymeric sensor PAA-Rho2 formed stable complexes with Au3+ through a large number of cation–dipole and ion–ion interactions. Moreover, the higher density carboxylic groups at the backbone of PAA-Rho interacted strongly with monodisperse superparamagnetic Fe3O4 NPs (FeNPs) which provided organic–inorganic hybrid fluorescence sensors (PAA-Rho2-FeNPs). The lower detection limit of the hybrid sensor toward Au3+ (0.85 μM) was less than that obtained from PAA-Rho2 (11.40 μM), and the response time was less than 40 seconds. Reusability was evaluated by repeating dipping and rinsing cycles in aqueous Au3+ and EDTA solutions. This approach may provide an easily measurable and inherently sensitive method for Au3+ ion detection in environmental and biological applications.

Self-assembly and electrochemical oxidation of polyamidoamine-carbazole dendron surfmer complexes: nanoring formation.

We report a detailed and quantitative study on the supramolecular complexation of amine-functionalized polyamidoamine (PAMAM) dendrimer G(4)-NH(2) with carboxylic acid terminal dendrons containing peripheral electroactive carbazole groups of different generations (G(0)COOH, G(1)COOH, and G(2)COOH). While the focus is on a detailed understanding and mechanism of complex formation, subsequent electrochemical oxidation of the dendron surfmers resulted in the formation of nanoring structures electrodeposited on the conducting substrate. Complexation was confirmed by NMR, UV-vis, and IR measurements. Critical micelle concentration (CMC), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) studies revealed that the ringlike structures were formed during the equilibrium-decomplexation stage and that the electrochemical process did not destroy the complex but rather stabilized it. The different generations of the dendrons provided various structures and complex formation efficacy. This type of template polymerization combined with electrochemically anodic oxidation has not been previously reported.

Inclusion Compounds Formed from N,N-bis(2-hydroxybenzyl)alkylamine Derivatives and Transition Metal Ions via Molecular Assembly

A series of N,N-bis(2-hydroxybenzyl)alkylamine derivatives (1–5) have been found to form host–guest compounds with transition metal ions. The inclusion phenomena in solution are confirmed from the new peak at 415 nm observed by UV-Vis (ultraviolet-visible) spectroscopy and the aromatic and methylene peak shifts observed by 1H NMR (proton nuclear magnetic resonance) spectroscopy. Comparative studies on 1–5 by liquid–liquid extraction studies suggest that the bulky group at the aza position of the derivatives obstructs the ion interaction resulting in the decrease in ion extraction ability. Inclusion depends on the interaction of the transition metal ions with the compounds 1–5 at the aza and hydroxyl groups as identified by the two-dimensional nuclear Overhauser enhancement technique (1H–1H NOESY). The results from Jobs plot and electrospray ionization mass spectroscopy (ESIMS) imply molecular assembly of the host–guest system in a 2:1 ratio. Comparative studies among different ions, i.e., Cu2+, Zn2+ and Cd2+ suggest that the host–guest formation is effective when electron sharing is possible through the outer orbital of the transition metal ions. In the case of inclusion in the solid state, the FTIR (Fourier transform infrared) spectra show the changes in vibrational mode of the functional groups in host molecules whereas the X-ray diffraction (XRD) patterns suggest a change in the packing structure of the host molecules. After host–guest formation, the thermal stability of the host molecules decreases as a result of the change in the packing structure from a hydrogen-bonded network to one of ionic interaction with the guest.

Redox nanoreactor dendrimer boxes: in situ hybrid gold nanoparticles via terthiophene and carbazole peripheral dendrimer oxidation

π-Conjugated dendrimer-protected gold nanoparticles in stable colloidal form have been successfully prepared via simultaneous reduction of AuCl3 with oxidative polymerization of terthiophene (PT) and carbazole (PC) peripheral functionalized polyamidoamine (PAMAM) dendrimers. The hybrid dendrimer–metal materials were characterized by UV-vis, fluorescence, and FT-IR spectroscopy. XPS and AFM analyses were also employed. The differences in gold nanoparticle (AuNP) formation between the two PAMAM derivatives were discussed. In case of PT dendrimer, AuNPs can be stabilized in situ to form PAMAM–PPT–AuNP hybrid materials. For the PC dendrimer, the redox reaction afforded carbazole polymerization without necessarily forming AuNPs.

Synthesis of unsymmetrical calix[4]arene cryptand crown-6 in 1,3-alternate conformation

Abstract We report the synthesis of a calix[4]arene bridged by a cryptand unit and a crown ether chain in 1,3-alternate conformation. Preliminary complexation properties with alkali metals are also described.

Optical chemosensors for Hg2+ from terthiophene appended rhodamine derivatives: FRET based molecular and in situ hybrid gold nanoparticle sensors

A multifunction sensor based on rhodamine B with a terthiophene substituent has been developed as a highly sensitive chemosensor for Hg2+. This method is mainly based on Hg2+-induced spirocycle opening leading to fluorescence and colorimetric enhancement. The binding properties of a terthiophene appended rhodamine based fluorescence chemosensor (RhoT) was studied using the fluorescence resonance energy transfer (FRET) process, and RhoT displayed highly selective fluorescence enhancement and a color change in the presence of Hg2+. Moreover, the in situ formation of gold nanoparticle/conducting polymer nanocomposite based-chemosensors (AuNPs-RhoT) was achieved to explore the sensitive and selective detection of Hg2+ in aqueous solution over 12 other metal ions using a colorimetric technique. The hybrid sensor became aggregated in solution in the presence of Hg2+ by an ion-templated chelation process, which caused an easily measurable change in the emission spectrum of the particles and provided an inherently sensitive method for Hg2+ detection in aqueous solution.

Conformation-Selective Synthesis and Binding Properties of N-Benzylhexahomotriaza-p- chlorocalix(3)trinaphthylamide

N-benzylhexahomotriaza-p-chlorocalix[3]trinaphthylamide in partial cone conformation was selectively synthesized by appropriately controlling the steric effect during the amidation reactions of N-benzylhexahomotriaza-p-chlorocalix[3]tri(ethyl acetate) in cone or partial cone conformations with use of 1-aminomethylnaphthalene. The conformation was confirmed by (1)H, (13)C, and 2D NMR and X-ray single-crystal analysis. Analyses of the complexes revealed that recognition is strongly affected by Cd(2+), Pb(2+), and F(-) ions.

Synthesis of 1,3-alternate calix[4]-cyclen-benzo-crown-6 as a hard–soft receptor

Abstract 1,3-Alternate calix[4]-cyclen-benzo-crown-6 incorporating a cyclen subunit on one side and a benzo-crown-6 on the other side of the calix[4]arene framework has been synthesized. Preliminary complexation studies of this macropolycycle with cesium and zinc picrate salts have been carried out by means of proton nuclear magnetic resonance spectroscopy.