摘要:

Steady-state phosphorescence measurements have been carried out for the quenching of benzophenone triplet state by several transition metal β-diketonate complexes. The results suggest a complex quenching mechanism in which energy and electron transfer processes might be involved.

ISSN:0038-7010    

DOI:10.1080/00387019008054043

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new, simple and sensitive fluorimetric method for the determination of three pharmaceutical thiocompounds: cimetidine, thiabendazole and carbimazole, and also allopurinol, has been presented. The method is based on the fluorescence quenching of mercurochrome (MER) in an aqueous alkaline medium. Calibration graphs correlating the fluorescence difference (Fo-F) or the fluoresence ratio (Fo/F) of MER before (Fo) and after (F) quencher addition versus the concentration of the latter are linear. Such linearity permitted the successful application of

ISSN:0038-7010    

DOI:10.1080/00387019008054044

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A new crystalline octahedral hexaaqua Ni(II) bis(o-tolylazo-citrazinate)hexahydrate complex was synthesized. The analytical data proved the formation of 1:2 stoichiometry. An X-ray structure investigation has been carried out. The triclinic space group is p and the unit cell parameters are a = 585.5 pm, b = 993 pm, c = 1139.4 pm, α = 101.6°, β = 97.4°, γ = 102.4°. Evaluation of intensity data revealed the structure with an R-value of 0.03 (2316 observed independent reflections). The compound consists of hexaaqua nickel(2+) ions, univalent anions of the carboxylic acid and six additional water molecules per

ISSN:0038-7010    

DOI:10.1080/00387019008054045

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The1H and13C NMR spectra of methaqualone,1, have been extensively studied using one and two-dimensional techniques. These 300 MHz1H and 75 MHz13C studies have allowed rigorous assignments to be made for the methyl groups and the quinazolinone nucleus. The 60 MHz1H spectra for1in CDCl3have been examined with

ISSN:0038-7010    

DOI:10.1080/00387019008054046

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

In molecules such as ΦX1X2X3the intensity of the secondary transition of the benzene chromophore, strongly depends on long range interactions involving a σ·π coupling between orbitals belonging to the Cα-X bonds, and the πΦ system. Such a coupling distorts the symmetry of the πΦsystem(1–5). The secondary transition (towards 260 nm) which is forbidden when the symmetry is D6h- as in the benzene molecule itself where only the low intensity progression A isobserved - becomes all the more allowed as the substituent is able to distort the πΦ cloud towards a C2Vsymmetry. A new progression called B is observed. Its intensity is usually evaluated by the measure of its 00 band. The distorsion of symmetry arises because of the π donating or π withdrawing electronic effects of the substituent(1–7). These phenomena have been explained on the ground of a V shaped function(l) : ϵ00= f(σ), where σ is a parameter linked to the electronic effects of the substituents. When the whole substituent is a π donating one, its π donating effect is lowered by an increase of the electron attracting power of the groups X : the perturbation of the D6hsymmetry is lessened and ϵ00decreases. On the contrary, when the whole substituent is a π withdrawing one, an increase of the withdrawing power of the groups X increases the withdrawing power of the whole substituent, the distorsion of the D6h symmetry increases and ϵ00increases too. The minimum of the V shaped curve correspond to the species for which the π donating tendency of the aliphatic part of the substituent is quenched by the electron withdrawing tendency of the groups X. The D6hsymmetry of the πΦ cloud is restored. The transition is forbidden and the system A only is observed.

ISSN:0038-7010    

DOI:10.1080/00387019008054047

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Aqueous cobalt(II) ion is shown to be an effective chemical shift reagent for nitrogen-14 nuclear magnetic resonance spectroscopy. Addition of an 8 fold excess of cobalt (II) ion to a mixture of betaine, glycerophosphorylcholine and ammonium ion results in baseline resolution of the three components. The chemical shift of each component is a function of cobalt concentration up to a molar ratio of about 4:1 after which, the shifts

ISSN:0038-7010    

DOI:10.1080/00387019008054048

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The electronic absorption spectra and luminescent properties in the first singlet π-π* excited states of aminophenol cations in aqueous solutions are studied from a theoretical and experimental point of view. Lifetime and quantum yield measurements are used in the electronic description of the first excited state. Cresols as isoelectronic species of these cationic compounds are used in order to stablish the nature of the main deactivation pathways in excited state.

ISSN:0038-7010    

DOI:10.1080/00387019008054049

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

This is a scanned image of the original Editorial Board page(s) for this issue.

ISSN:0038-7010    

DOI:10.1080/00387019008054042

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor