摘要:

AbstractExcited‐state double proton transfer (ESDPT) has been studied in a variety of 1‐azacarbazole (1AC) hosted hydrogen‐bonded complexes. In 1 AC/carboxylic acids hydrogen bonded complexes, large association constants of>1.0 × 104M−1are measured in the ground state and the rate of ESDPT is » 5.0 × 109s−1, resulting in a dominant proton‐transfer tautomer emission. In several 1 AC/lactam hydrogen bonded complexes, however, spectral and dynamic results show the existence of a fast excited‐state equilibrium between normal and proton‐transfer tautomer states. The result can be tentatively rationalized by a non‐catalytic ESDPT mechanism incorporating tautomerization energy o

ISSN:0009-4536    

DOI:10.1002/jccs.199600067

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

Abstractγ‐Aminobutyrohydroxamate resin that simulate siderophore analogues was prepared. The structure and conversion of functional groups of the resin were confirmed with IR spectra and elemental analysis. The influence of pH on adsorption of metal ions to the resin was examined. Uptake of metal ions increased with pH and was quantitative in the pH range of 4 to 6 for most of the lanthanides. These metal ions showed high exchange rates towards the resin. The complexation behavior of the resin was also investigated by means of IR and potentiometry. The dissociation constant, pKaof the hydroxamic hydroxyl group is 9.36. Stability constants of the insoluble lanthanide complexes on the resins were measured potentiometrically at 25 ± 0.1 °C and ionic strength of 0.1 M KCl. The results were compared with those of the corresponding soluble lanthanide complexes. It was found that a higher stability of the resin resulted in an increase of the stability constants. The phenomena might be due to the length of the spacer in providing the proper geometry of the resin ligand for intramolecular metal complexa

ISSN:0009-4536    

DOI:10.1002/jccs.199600068

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThis study concerns with treatment of polycrystalline gold surface with square wave potential program to enhance the signal of electrochemical oxidation of glucose. After such perturbation the glucose oxidation wave is increased almost ten times. Consequently, gold is a useful electrode for sensor applications.

ISSN:0009-4536    

DOI:10.1002/jccs.199600069

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractReaction of [MoCo(CO)5(PPh3)2(η5‐C5H5)] (1) with diphenylacetylene in tetrahydrofuran at 50 °C yielded two heterobimetallic compounds, [MoCo(CO)4.(PPh3){μ‐PhC  CPh}(η5‐C5H5)] (4) and [MoCo(CO)5{μ‐PhC  CPh} (η5‐C5H5)] (5). However, an unexpected product, Co(CO)2(μ‐CO)(μ:η2,η4‐C4Ph4)Co(CO)2(PPh3) (6), was observed while attempting to grow the crystals for structural determination of 4. The X‐ray crystal structure of 6 was determined: triclinic,\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm P}\bar 1 $\end{document}, a = 11.654(2) Å, b = 12.864(2) Å, c = 13.854(2) Å, α = 89.67(2)°, β = 86.00(2)°, γ= 83.33(2)°, V = 2057.9(6) Å3Z=2. In 6, two cobalt fragments are at apical and basal positions of the pseudo‐pentagonal pyramidal structure, respectively. The electron count for the apical cobalt fragments is 20, which is rather unusual. It is believed that 6 was formed after the fragmentation and rec

ISSN:0009-4536    

DOI:10.1002/jccs.199600070

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe antihypertensive activity of dl‐tetrahydropalmatine hydrochloride (THP), isolated from the tubers of Corydalis racemosa (Thunb.) Pers. (Papaveraceae), was investigated in spontaneously hypertensive rats (SHRs) using intravenous injection. A dose‐dependent lowering of blood pressure was observed in SHRs. Decrease of plasma noradrenaline was also obtained in SHRs that received injection of THP. Direct injection of THP into brain lowered the blood pressure and plasma noradrenaline. This antihypertensive action of THP appears to be produced mainly by an effect on central nervous system to lower sympathetic tone in S

ISSN:0009-4536    

DOI:10.1002/jccs.199600071

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractSeveral new pyrazolo[5,I‐c]triazine, selenadiazoline, thiadiazoline, selenadiazolo[3,2‐a]quitiazolone, and arylazothiazole derivatives were synthesised by the reaction of hydrazonoyl halides with different reagents. The structure of new heterocycles were assigned on the basis of their elemental analysis, spectral data, and alternate synthesis whenever possi

ISSN:0009-4536    

DOI:10.1002/jccs.199600072

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe products from the condensation of acetone‐anils (1) and TCNE reaction were characterized after separation. The main products, tricyanoethylene derivatives (7–9) were isolated with the malonodinitrile derivatives (10–12), respectively. The [2+2] cycloaddition product (13), namely 5‐methoxy‐3,4‐(2′,2′,3′,3′‐tetracyanocyclobutano)‐l,2‐dihydro‐2,2,4‐trimethylquinoline also has been isolated. The distribution of these three prod

ISSN:0009-4536    

DOI:10.1002/jccs.199600073

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe enantioresolution of thirteen methylthiohydantoin‐amino acids (MTH‐amino acids), which are substrates for producing D‐amino acids through enzyme‐catalyzed hydrolysis, is described onR, S‐2‐hydroxypropyl derivatized β‐cyclodextrin bonded stationary phase (RSP‐β‐CD CSP) with a water‐based mobile phase. The enantioresolution is relatively sensitive to the structural variation of group which is attached to the carbon at position five on methylthiohydantoin moiety and subsequently turns into side‐chain group of corresponding D‐amino acid produced after hydrolysis. The inclusion complexation is believed to be the mechanism responsible for the observed enantioresolution that cannot be reproduced either on native β‐cyclodextrin CSP under the same chromatographic conditions or on both CSPs using the acetonitrile‐based mobile phase. Approaches for enantioimprovement include varying the percentage of organic modifier in the mobile phase and using the buffer‐typed mobile phase such as t

ISSN:0009-4536    

DOI:10.1002/jccs.199600074

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractThe relative rates for the addition reactions oftert‐butyl radical to 2‐substituted ally chlorides I have een determined. The correlation of log k/k0, vs. σmgives a ρ mvalue of 3.59 with correlation coefficient of 0.930. When the substituent CH2Cl is excluded, correlation coefficient raises to 0.990 and ρ value becomes 3.39. The large p value and the deviation of relative rate of substituent CH2C1 are dis

ISSN:0009-4536    

DOI:10.1002/jccs.199600075

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY

摘要:

AbstractFour naphthoquinones together with one known naphthoquinone were isolated from the stems ofDiospyros maritimaBlume. Four naphthoquinones were elucidated as 2,2′‐, 2,3′‐, 3,2′‐, and 3,3′‐diethoxy‐isodiospyrins, respectively, on the basis of sp

ISSN:0009-4536    

DOI:10.1002/jccs.199600076

出版商:WILEY‐VCH Verlag    

年代:1996

数据来源: WILEY