A STUDY OF THE KINETICS OF INCLUSION OF HALONAPHTHALENES WITH ß-CYCLODEXTRIN VIA TIME CORRELATED PHOSPHORESCENCE

Abstract— The phosphorescence of 1-bromonaphthalene and 1-chloronaphthalene is readily observable in nitrogen purged aqueous solutions containing ß-cyclodextrin. Addition of acetonitrile increases both the phosphorescence intensity and lifetime. The quenching of halonaphthalene phosphorescence in aqueous solution by nitrite is substantially inhibited upon addition of ß-cyclodextrin, as a result of a guest-host complex. The rate constants for formation and dissociation of the l-bromonaphthalene/ß-cyclodextrin complex are evaluated from an analysis of the dependence of phosphorescence lifetimes on nitrite concentration.     

Structural requirements of flavonoids and related compounds for aldose reductase inhibitory activity

The methanolic extracts of several natural medicines and medicinal foodstuffs were found to show an inhibitory effect on rat lens aldose reductase. In most cases, flavonoids were isolated as the active constituents by bioassay-guided separation, and among them, quercitrin (IC(50)=0.15 microM), guaijaverin (0.18 microM), and desmanthin-1 (0.082 microM) exhibited potent inhibitory activity. Desmanthin-1 showed the most potent activity, which was equivalent to that of a commercial synthetic aldose reductase inhibitor, epalrestat (0.072 microM). In order to clarify the structural requirements of flavonoids for aldose reductase inhibitory activity, various flavonoids and related compounds were examined. The results suggested the following structural requirements of flavonoid: 1) the flavones and flavonols having the 7-hydroxyl and/or catechol moiety at the B ring (the 3',4'-dihydroxyl moiety) exhibit the strong activity; 2) the 5-hydroxyl moiety does not affect the activity; 3) the 3-hydroxyl and 7-O-glucosyl moieties reduce the activity; 4) the 2-3 double bond enhances the activity; 5) the flavones and flavonols having the catechol moiety at the B ring exhibit stronger activity than those having the pyrogallol moiety (the 3',4',5'-trihydroxyl moiety).     

Reaction of (bromodifluoromethyl)phenyldimethylsilane with organometallic reagents

A new fluorine-containing organosilicon compound, (bromodifluoromethyl)-phenyldimethylsilane (II), was synthesized by the N-bromosuccinimide (NBS) bromination of difluoromethyl)phenyldimethylsilane (I), which was prepared from phenyldimethylsilyllithium and chlorodifluoromethane. Compound II reacted with dimethyl sulfoxide to give dimethyl sulfide and phenyldimethylfluorosilane in quantitative yield. The reaction of II with nucleophiles, such as sodium ethoxide, Grignard or lithium reagents, afforded products arising from cleavage of the carbonsilicon bond. In contrast, the reaction of II with Grignard reagents in the presence of appropriate catalysts (Group VIII transition metal salts or complexes) afforded the homo-coupling product of II, 1,2-bis-(phenyldimethylsilyl)-1,1,2,2-tetrafluoroethane (IV), in excellent yield. The silver(I) salt-catalyzed reaction of II with ethylmagnesium bromide gave the cross-coupling product, (1,1-difluoropropyl)phenyldimethylsilane (V) as well as III and IV. When cuprous bromide was employed as catalyst, the reaction of II with ethylmagnesium bromide afforded 1-phenyldimethylsilyl-1-propene (VI) and 3-phenyldimethylsilyl-2-pentene (VII) as main products.     

Synthesis and Properties of Highly Conductive Thin Films as Buffer Layer from Sol-Gel Process

We prepared epitaxial growth SrRuO₃ thin film on LaAlO₃ (001) (LAO) single crystal substrate and highly oriented BaTiO₃ ferroelectric thin film on the epitaxial SrRuO₃ thin film. A homogeneous precursor solution for preparing SrRuO₃ thin film was prepared with Sr(O—i—C₃H₇)₂ and Ru(NO)(NO₃)₃ as starting materials, and 2-methoxy ethanol as solvents. The as-coated thin films were heat treated at temperatures from 723 to 1273 K for 1 h in air. SrRuO₃ grew epitaxially on LAO(001) substrate, which were confirmed by XRD theta-2theta method and XRD pole figure analysis. The crystallographic relationship of the film and substrate was SrRuO₃(001) parallel to LAO(001) and SrRuO₃[110] parallel to LAO[100]. A homogeneous precursor solution for preparing BaTiO₃ thin film was prepared with Ti[O—n—(CH₂)₃CH₃]₄ and Ba(OCOCH₃)₂ as starting materials, and acetic acid, 2-methoxy ethanol. SrRuO₃ coated LAO substrates were coated by spin-coating method with the coating solution. The as-coated thin films were heat treated at temperatures from 973 to 1173 K in air. It was confirmed that the thin films were growing orientated for c-axis by measurement of XRD theta-2theta method.     

Extraction-spectrophotometric determination of traces of antimony in copper and lead metals and in lead-base alloy with pyrocatechol violet and tri-n-octylamine

A sensitive spectrophotometric method is described for the determination of antimony in copper and lead metals and in lead-base alloy. Optimal conditions have been established for the extraction and determination of antimony. Antimony (III) is extracted from a potassium iodide—sulfuric acid or a hydrobromic—sulfuric acid medium with toluene and converted to an antimony-pyrocatechol violet (PV) complex. The complex is then extracted with tri-n-octylamine (TOA) and the absorbance of the resulting ternary Sb(III)—PV-TOA complex is measured at 555 nm. As little as 0.5 p.p.m. of antimony in copper metal and 0.2 p.p.m. of antimony in lead metal and lead-base alloy can be determined.     

Convenient scaffold for forming heteroporphyrin arrays in aqueous media

A new methodology for preparing heteroporphyrin arrays in aqueous solution has been presented. The present method is based on the extremely strong ability of heptakis(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMe-beta-CD) to include 5,10,15,20-tetrakis(p-substituted-phenyl)porphyrins (Por) affording trans-type 1:2 complexes of the porphyrins and TMe-beta-CD. Two different Por-per-O-methylated beta-CD (per-Me-beta-CD) conjugates were synthesized. Conjugate 2 was prepared by an S(N)2 reaction of 5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin and per-O-methylated beta-cyclodextrin having one primary OTs group. Four per-Me-beta-CD moieties are attached to the meso positions of 2. Conjugate 3, synthesized from 5-(p-hydroxyphenyl)-10,15,20-tris(3,5-dicarboxyphenyl)porphyrin and monotosylated per-O-methylated beta-cyclodextrin, has one per-Me-beta-CD moiety at the periphery of the porphyrin. Conjugate 2 yields a stable 1:4 complex with the zinc complex of 5-phenyl-10,15,20-tris(3,5-dicarboxyphenyl)porphyrin (8) in the dissociated form. In this system, the energy transfer from photoexcited Zn-8 to free base 2 occurs with 85% efficiency. Conjugate 3 forms a very stable 1:1 complex with Zn-8 (K = (7.0 +/- 0.3) x 10(5) dm(3) mol(-1)) with an energy transfer efficiency (93%) larger than that obtained in the case of 2. The structure of the 3-Zn-8 complex, which can account for the efficient energy transfer, was deduced from (1)H NMR spectroscopy. Intramolecular fluorescence quenching of 2 and 3 by Fe(III)-8 also occurred through an electron-transfer process as the main quenching mechanism. The present method is a very simple and convenient means to construct various heteroporphyrin arrays in aqueous solution.     

1,3-Dipolar cycloaddition of α-alkoxycarbonylnitrones with vinyl ethers and allyl alcohols in the presence of Eu(fod)3: selective activation of (Z)-isomers of the nitrones

Uncatalyzed cycloaddition of α-alkoxycarbonylnitrones 1 with vinyl ethers 7 gave mixtures of cis- and trans-cycloadducts 8, whereas Eu(fod)₃-catalyzed cycloaddition of 1 with 7 gave the trans-cycloadducts trans-8 in a highly stereoselective manner. NMR studies indicated that Eu(fod)₃ selectively activated (Z)-nitrones (Z)-1 in E,Z-equilibrium mixtures of nitrones 1. In contrast, the reaction of 1 with allyl alcohols 12 in the presence of Eu(fod)₃ resulted in sequential transesterification and intramolecular cycloaddition to give intramolecular cycloadducts 13.     

Macrocyclic hexaketone as a specific host of uranyl ion

A novel synthetic method was described for a new macrocyclic hexaketone, 1,3,9,11,17,19-hexaoxocyclotetracosane, which extracted 98 % of uranyl ion into benzene phase from a dilute (10 ppm) aqueous solution of pH 8.     

Observation of quantum coherence for recurrence motion of exciton in anthracene dimers in solution

The quantum beat signal associated with recurrence motion of exciton was observed for two types of anthracene dimers connected through a phenyl ring, on femtosecond fluorescence anisotropy decay. The time periods of oscillation were 0.3-0.9 ps, which correspond to exciton interactions of 30-50 cm-1, and the damping time constants (dephasing time) were 0.7-1.0 ps. The results show that the coherent aspect in photochemical processes is observable even in solution at room temperature, if one employs dimers of rigid structures.