Ambient temperature oxygen sensors based on fluoride solid electrolyte: the roles of the constituents in the sensing electrode mixtures containing phthalocyanines

The short-circuit-current response properties of ambient temperature oxygen sensors of the type, Ag|Ag(6)I(4)WO(4)|PbSnF(4)(PSF)| sensing electrode (SE), O(2); SE: mixtures of Pt-black/Pc's/PSF, carbon/Pc's/PSF, Pc's/PSF, Pt-black/PSF, carbon/PSF (phthalocyanines, Pc's: FePc, CoPc, CuPc, H(2)Pc) have been examined to elucidate the roles of the incorporated Pc's, Pt-black and carbon. FePc and CoPc act as the catalyst for the SE-reaction involving the two-electron reduction of oxygen, whereas CuPc and H(2)Pc have not such a catalytic action. The difference is related to the types of the first oxidation of Pc's, i.e. the central metal oxidation and the ligand oxidation. In addition, the sensitivity (S) and 90% response time (t(90)) depend on the oxidation potentials. FePc is the best of the Pc's used here in terms of t(90) (i.e. 40 s for the SE-mixtures of Pt-black/FePc/PSF and carbon/FePc/PSF). Although Pt-black acts as the catalyst, it tends to give rise to hysteresis, drifts and slow response. The undesirable effects are lessened by incorporating Pc's. For the Pt-black/FePc/PSF sensor, the response properties are almost dominated by the incorporated FePc and hence are comparable to those of the C/FePc/PSF sensors. This indicates that Pt-black can be substituted by carbon materials. The incorporated carbon has no such catalytic action. The role is to make the SE-mixtures more electronically conductive, resulting in the improvement of S and t(90).     

Investigation of intermolecular interaction in molecular complex of tryptamine and benzoic acid by solid-state 2D NMR

Solid-state NMR spectra and powder X-ray diffraction of the two-component molecular complex composed of tryptamine and benzoic acid were observed to investigate the intermolecular interaction in the molecular complex. 1D (13)C CP/MAS NMR spectrum and powder X-ray diffraction pattern of the complex was clearly different from the convolution of each spectrum of the single component. 2D (1)H-(13)C heteronuclear-correlation (HETCOR) NMR technique indicated that the intermolecular interaction between the primary amine of tryptamine and the carboxyl group of benzoic acid must be related to the complex formation.     

Polymerization of 1-methylthio-1-alkynes and polymer properties

Polymerization of 1-methylthio-1-alkynes (MeSC?CR; R = Et, n-Bu, n-C₆H₁₃, and n-C₈H₁₇) was studied by use of transition metal catalysts. A 1 : 2 mixture of MoCl₅ and Ph₃SiH provided polymers having M?_w over 1 × 10⁵ in 30–50% yields from these monomers. The length of the alkyl group hardly affected the polymerization. The monomer, MeSC?C-n-C₆H₁₃, showed low reactivity in homopolymerization, but higher reactivity than that of MeC?C-n-C₅H₁₁ in copolymerization. Poly(1-methylthio-1-alkyne)s were colorless solids, and those with long alkyl pendants (R = n-C₆H₁₃, n-C₈H₁₇) were soluble in various organic solvents. The present polymers were thermally more stable than poly(2-alkyne)s, the corresponding hydrocarbon polymers.     

Studies on antiatherosclerotic agents. Synthesis and inhibitory activities on platelet aggregation of 4-aryl derivatives of 7-ethoxycarbonyl-6,8-dimethyl-1 (2H)-phthalazinone.

4-Aryl derivatives of 7-ethoxycarbonyl-6,8-dimethyl-1(2H)-phthalazinone and related derivatives were newly synthesized in order to test for their inhibitory activities on platelet aggregation. 4-(2-Anisyl) compound and the corresponding 1-chloro derivative demonstrated significant activity.     

Synthesis of 2H-indazole-4,7-dione derivatives from 3-phenylsydnone and p-toluquinone. The crystal and molecular structure of 6-bromo-5-methyl-2-phenyl-2H-indazole-4,7-dione

The 1,3-dipolar cycloaddition of 3-phenylsydnone with p-toluquinone afforded 5-methyl- and 6-methyl-2-phenyl-2H-indazole-4,7-diones 3a and 3b. No regioselectivity was observed in this cycloaddition yielding an equimolar amount of the regioisomers. Reactions of 3a and 3b with bromine gave the corresponding mono- 4a and 4b and dibromo derivatives 5a and 5b , respectively. The crystal structure of 6-bromo-5-methyl-2-phenyl-2H-indazole-4,7-dione ( 4a ) has been determined by the single crystal X-ray method. The crystals are monoclinic, space group PI with two molecules in a unit cell of dimensions a = 8.029(1), b = 14.309(1), c = 5.895(1)Å, β = 90.24(1)° and V = 621 ų. The structure has been solved by the direct method using 1827 reflections and refined by full-matrix least-squares calculations to R = 0.0739.     

Structure and redox properties of electropolymerized film obtained from iron meso‐tetrakis(3‐thienyl)porphyrin

Oxidative polymerization of bromoiron(III) meso‐tetrakis(3‐thienyl)porphyrin gave a novel polymeric porphyrin complex randomly crosslinked at the 2,5‐positions of the peripheral thienyl groups. The electrical semiconductivity of ca. 10^?5 S/cm after I₂ doping indicated that the polymer had a π‐conjugated structure with a moderate delocalization of π electrons over the thienylporphyrin units. PM3 calculations for free‐base models revealed that HOCO (the highest occupied crystal orbital) band width was reduced by introduction of the porphyrin moieties into the thienylene backbone and yet low HOCO‐LUCO (the lowest unoccupied crystal orbital) gap was maintained, which accounted for the relatively low electrical conductivity of the porphyrin polymer. The modified electrode prepared by electropolymerization was redox‐active due to the presence of iron(II/III) couple and the semiconductivity of the film, which served as a novel non‐enzymatic electrochemical sensor for superoxide anion radical based on the facile electrocatalytic oxidation of the superoxide. Copyright © 2005 John Wiley & Sons, Ltd.     

Studies on hypotensive agents. Synthesis of 1-substituted 3-(2-chlorophenyl)-6-ethoxycarbonyl-5,7-dimethyl-2,4(1H,3H)-quinazoline diones.

3-(2-Chlorophenyl)-6-ethoxycarbonyl-5,7-dimethyl-2,4(1H,3H)-quinazoline dione was newly prepared. 1-Hydrogen atoms of the compound were variously substituted in order to test for their hypotensive activities on relaxing effects of the blood vessels. The compounds with 2-(1-pyrrolidinyl) ethyl, 2-(1-piperidinyl)ethyl, 3-(dimethylamino)propyl, and 3-(N-benzyl-N-methylamino)propyl moieties showed significant activity. The 2-(1-piperidinyl)ethyl compound possessed activity approximately 23 times more potent than papaverine, however, it was less potent than cinnarizine.     

Mass spectrometric fragmentation of the oxetanes of 3,5-dimethylisoxazole, 2,4-dimethylthiazole and 1-acetylimidazole

The mass spectra of the oxetanes of 3,5-dimethylisoxazole, 2,4-dimethylthiazole and 1-acetylimidazole have been studied with the aid of high resolution mass spectrometry. The spectra exhibit characteristic fragmentation patterns which are common to all these oxetanes and are classified as five processes.     

Electrochemical sensor for superoxide anion radical using polymeric iron porphyrin complexes containing axial 1‐methylimidazole ligand as cytochrome c mimics

A needle‐type electrochemical sensor for the facile detection of superoxide anion radical (O) was devised using an electrodeposited film of a polymeric porphyrin complex attached to a carbon microelectrode which was placed in a stainless steel 18G needle tube as an auxiliary electrode. The sensing element was prepared by means of electropolymerization of bromoiron(III) meso‐ tetra(3‐thienyl)porphyrin in the presence of 1‐methylimidazole in CH₂Cl₂ containing 100 mM tetrabutylammonium perchlorate (TBAP) as a supporting electrolyte, which gave a smooth film of the corresponding polymer. The film was electrochemically active to give a redox response near −0.05 V versus Ag/AgCl due to the iron(II/III) couple. The microsensor was applied to detect O produced by xanthine oxidation catalyzed by xanthine oxidase. The amperometric response for O was monitored at an electrode potential of 0.5 V versus the auxiliary electrode in a 10 mM phosphate buffer. The microsensor displayed a high catalytic activity for the oxidation of O and showed a linear relationship between the current and the O concentration. Axial coordination of an imidazole ligand to the iron porphyrin center enhanced selectivity for O by impeding the undesired coordination of H₂O₂ that resulted from the dismutation of O. Copyright © 2005 John Wiley & Sons, Ltd.     

Supramolecular design for multivalent interaction: maltose mobility along polyrotaxane enhanced binding with concanavalin A

High molecular mobility of maltose-conjugated alpha-cyclodextrins (alpha-CDs) along a poly(ethylene glycol) (PEG) chain due to the mechanically locked structure of polyrotaxanes enhanced multivalent interactions between maltose and concanavalin A (Con A). When maltose groups are conjugated with alpha-CDs that were threaded onto a PEG capped with benzyloxycarbonyl l-tyrosine (polyrotaxane), Con A-induced hemagglutination was greatly inhibited by polyrotaxanes with a certain threading % of alpha-CDs. Such an inhibitory effect was significantly superior to the other type of conjugates, in which poly(acrylic acid) was used as a backbone for maltose conjugation. The spin-spin relaxation time (T2) of the maltose C(1) proton in the polyrotaxane at a typical alpha-CD threading % was significantly larger than that of any other conjugate, which was well related to the inhibitory effect. Therefore, we concluded that the high mobility of maltose groups along the polyrotaxane structure contributes to enhanced Con A recognition.