Host-guest sensory system of sodium anthranilate-modifiedβ-cyclodextrin: Molecular recognition properties

Sodium anthranilate-modified-cyclodextrin (1) has been prepared as a sensor for detecting organic compounds including terpenoids and steroids.1 shows a pure monomer fluorescence whose intensity is increased or decreased upon addition of the guest species examined. In this system, the sodium anthranilate moiety acts either as a spacer, which enables the cyclodextrin to form a 11 guest complex by narrowing the-cyclodextrin cavity or acts as a hydrophobic cap.1 shows a higher sensitivity for terpenoids than for steroids, but has a higher selective molecular recognition ablity for steroids than for terpenoids.     

Edge zeta functions of hypergraphs

We introduce the edge zeta function of a hypergraph and present its determinant expression. Furthermore, we give a decomposition formula for the edge zeta function of a group covering of a hypergraph. Finally, we present two new determinant expressions for the edge zeta function of a hypergraph.     

Nanometer‐sized polyradical particles: Organic magnetic dot array formed on a silicon microfabricated substrate

A magnetically active, purely organic dot array was formed by the selective deposition of polyradical nanoparticles on array‐like‐formed pits on a silicon substrate. The nanometer‐sized polyradical particles, poly(4‐methacryoyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐oxyl), were prepared by the emulsion polymerization of 4‐methacryloyloxy‐2,2,6,6‐tetramethylpiperidine‐1‐acetoxyl followed by a deprotection reaction and oxidation in air. The size (diameter) and radical spin concentration of the polyradical nanoparticles were tunable between the polymerization and oxidation conditions. Electrochemical studies revealed the redox property of the polyradical nanoparticles. The magnetic response image of the polyradical nanoparticles was obtained by magnetic force microscopy, reflecting their radical spin concentrations. These results suggested a possible approach for the use of organic polyradical nanoparticles as organic magnetic dot arrays. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 521–530, 2007     

A reduction of the high symmetry of C60 in a PMMA polymer film as revealed by electroabsorption spectra

The absorption band of C₆₀ and C₇₀ located at 331 nm and 380 nm, respectively, in a PMMA polymer film shows a strong electric field effect, and the observed electroabsorption spectra are simulated by a superposition of the absorption spectrum, its first and the second derivative spectra, suggesting that electric dipole moment and molecular polarizability change following excitation into these bands. The presence of the electric dipole moment implies that inversion center does not exist in a polymer film not only on C₇₀ but also on C₆₀ in the ground state or/and the excited state.     

Droplet electrocoupling between capillary electrophoresis and matrix assisted laser desorption/ionization-time of flight-mass spectroscopy and its application.

A droplet of an electroconductive solution was put on the sample plate of a matrix-assisted laser desorption/ionization-time of flight-mass spectroscope (MALDI-TOF-MS) and the outlet terminal of a capillary Electrophoresis (CE) capillary was put into this droplet in order to make an electro-connection and to apply high voltage between the metallic sample plate and the counter pole of the CE. This procedure was simple and gave much more stable interfacing than that of the electrospray method. Furthermore, the separated component was collected and concentrated in a droplet. By mixing each separated sample spot with the MALDI matrix on the sample plate, the spots were analyzed in separated sequences to make three-dimensional mass chromatograms, or applied to the enzyme digestion analysis for peptide sequencing.     

Recognition of bile acids at cyclodextrin-modified gold electrodes.

Lipoylamino-beta- and gamma-cyclodextrin (LP-beta-CD and LP-gamma-CD, respectively) were adsorbed at the surface of gold electrodes by sulfur-gold bonding. The resultant electrodes exhibited quasi-reversible voltammograms for the redox reaction of Fe(CN)6(3-/4-) in aqueous solutions, with peak-to-peak separation (deltaEp) being 85 mV at 20 mV s(-1) as a potential sweep rate. When bile acids are added to the solution, deltaEp values increased to 200-300 mV with increasing the concentration of bile acids. A Langmuir-type adsorption analyses satisfactorily afforded the binding constants (Ksurf) of the surface-confined LP-beta-CD and LP-gamma-CD with the bile acids. The obtained Ksurf values of LP-gamma-CD are 5.0-50 times larger than the corresponding binding constants of gamma-CD in homogeneous aqueous solutions. Cyclic voltammetric experiments with positively, negatively, and non-charged adamantane derivatives as well as pH titration experiments revealed that the retardation of the electrode reaction of negatively charged Fe(CN)6(3-/4-) caused by bile acids was attributable (1) to electric potential changes due to the accumulation of the negative charges at the electrode surface, and (2) to an increase in the hydrophobicity of the electrode surface due to the binding of hydrophobic bile acids to the LP-beta-CD and LP-gamma-CD membranes.     

Three characteristic reactions of alkynes with metal compounds in organic synthesis

Alkynes have two sets of mutually orthogonal π‐bonds that are different from the π‐bonds of alkenes. These π‐bonds are able to bond with transition metal compounds. Alkynes easily bond with the various kinds of compounds having a π‐bond such as carbon monoxide, alkenes, other alkynes and nitriles in the presence of the transition metal compounds. The most representative reaction of alkynes is called the Pauson–Khand reaction. The Pauson–Khand reactions include the cyclization of alkynes with alkenes and carbon monoxide in the presence of cobalt carbonyls. Similar Pauson–Khand reactions also proceed in the presence of other transition metal compounds. These reactions are the first type of characteristic reaction of alkynes. Other various kinds of cyclizations with alkynes also proceed in the presence of the transition metal compounds. These reactions are the second type of characteristic reaction of alkynes. These include cyclooligomerizations and cycloadditions. The cyclooligomerizations include mainly cyclotrimerizations and cyclotetramerizations, and the cycloadditions are [2 + 2], [2 + 2 + 1], [2 + 2 + 2], [3 + 2], [4 + 2], etc., type cycloadditions. Alkynes are fairly reactive because of the high s character of their σ‐bonds. Therefore, simple coupling reactions with alkynes also proceed besides the cyclizations. The coupling reactions are the third type of characteristic reactions of alkynes in the presence of, mainly, the transition metal compounds. These reactions include carbonylations, dioxycarbonylations, Sonogashira reactions, coupling reactions with aldehydes, ketones, alkynes, alkenes and allyl compounds. Copyright © 2008 John Wiley & Sons, Ltd.     

Supramolecular probe for bicarbonate exhibiting anomalous pyrene fluorescence in aqueous media

Highly selective HCO3- sensing is realized in a pH 8.6 aqueous solution on the basis of the HCO3--induced anomalous pyrene fluorescence of an association dimer that consists of pyrene-appended gamma-cyclodextrins having a triamine linker. The anomalous fluorescence that is produced by the HCO3--induced twisted conformation of the pyrene residues in the association dimer is insensitive to the presence of other anions.     

Reactions of 1-naphthols with pi-acceptor p-benzoquinones: oxidative aryl coupling vs. non-oxidative electrophilic arylation

We investigated the reactions of various 1-naphthols (NPOHs; 1) with p-benzoquinones (Qs), such as 1,4-benzoquinone (BQ) and p-chloranil (CA), as pi-electron acceptors. With electron-rich NPOHs 1a-c, oxidative biaryl coupling and subsequent dehydrogenation reaction took place selectively to give the corresponding 2,2'-binapthyl-1,1'-quinones 3a-c in excellent yield. In the case of electron-deficient NPOHs 1e, f, two different types of reactions occurred in the presence of SnCl4 and ZrO2 under similar conditions: SnCl4 mediated oxidative dimerization and trimerization of NPOH, while ZrO2 promoted electrophilic arylation of Qs with NPOH. The resulting products 3 would be useful synthetic intermediates for naturally occurring diosindigo B, biramentaceone and violet-quinone.     

Reactions of triethylsilyl thiophenoxide with ketones having an electron-with-drawing group on the α-carbon

Triethylsilyl thiophenoxide has been found to react with easily enolizable ketones to give silyl enol ethers; these have also been synthesized by a Rh^I complex catalysed reaction of triethylsilane with enolizable ketones in the presence of a small amount of silyl thioether or thiophenol.