Fluorescence enhancement of a signaling system in the simultaneous presence of transition and alkali metal ions: a potential AND logic gate

Attachment of a laterally non-symmetric cryptand and a macrocycle at the 9- and 10-positions of anthracene leads to a fluorescent signaling system L1 which gives fluorescence enhancement in the simultaneous presence of alkali and transition metal ions.     

Attachment of electron-withdrawing 2,4-dinitrobenzene groups to a cryptand-based receptor for Cu(II)/H+ specific exciplex and monomer emissions

[reaction: see text] In a cryptand-based fluorescent signaling system with the configuration "fluorophore-spacer-receptor", attachment of the electron-withdrawing 2,4-dinitrobenzene groups to the cryptand receptor renders it highly selective for Cu(II). The system exhibits dual monomer and exciplex emissions in the presence of either of Cu(II) and H(+) as input with concomitant movements of one of the 2,4-dinitrobenzene groups.     

Synthesis of furan-fused 1,4-dihydrocarbazoles via an unusual Garratt-Braverman Cyclization of indolyl propargyl ethers and their antifungal activity

The reactivity of indole based bis-propargyl ethers 4a-4g under Garratt-Braverman condition (KOBu^t in refluxing toluene) has been studied. Interestingly, these propargyl systems with one arm attached with substituted 3-indolyl derivatives leaving the other arm unsubstituted produced the 3,4-furan fused dihydrocarbazole derivatives 6a-6g (and not the expected carbazole derivatives) as the predominant product (70–82%) making this methodology to access such derivatives an attractive route. The results are supported by computational studies and some of the carbazole derivatives showed good antifungal activities.     

Solution of quantum Langevin equation: approximations, theoretical and numerical aspects

Based on a coherent state representation of noise operator and an ensemble averaging procedure using Wigner canonical thermal distribution for harmonic oscillators, a generalized quantum Langevin equation has been recently developed [Phys. Rev. E 65, 021109 (2002); 66, 051106 (2002)] to derive the equations of motion for probability distribution functions in c-number phase-space. We extend the treatment to explore several systematic approximation schemes for the solutions of the Langevin equation for nonlinear potentials for a wide range of noise correlation, strength and temperature down to the vacuum limit. The method is exemplified by an analytic application to harmonic oscillator for arbitrary memory kernel and with the help of a numerical calculation of barrier crossing, in a cubic potential to demonstrate the quantum Kramers' turnover and the quantum Arrhenius plot.     

Quantum escape kinetics over a fluctuating barrier

The escape rate of a particle over a fluctuating barrier in a double-well potential exhibits resonance at an optimum value of correlation time of fluctuation. This has been shown to be important in several variants of kinetic model of chemical reactions. We extend the analysis of this phenomenon of resonant activation to quantum domain to show how quantization significantly enhances resonant activation at low temperature due to tunneling.     

Spectrophotometric estimation of molybdenum with disodiom cis-1,2-dicyanoetfaylene-1,2-dithiolate

A rapid spectrophotometnc method is described for estimation of molybdenum by use of the molybdenum-dicyanoethytene dithiolate complex. The bright green complex has its absorption maximum at 665 nm and in 50% aqueous acetonitrilc is stable for several days at 3M hydrochloric add concentration, The estimation is more sélective if longer wavelengths and high acidity are used. Beer's law is obeyed over the range 1-16 ppm molybdenum, optimum range 4-16 ppm. The overall formation constant Of the complex with metal to ligand ratio of 1:4 is 5 +/- 2 x 10(18). The molar absorptivity is 5.05 x 10(3) l.mole(-1).cm(-1).     

Spectrophotometric determination of iron with chelidamic acid

Summary Chelidamic acid forms with iron a complex at p_H 5.8 to 8.5 having the maximum absorption at 460 nm. The metal to reagent ratio is 13 and the instability constant is about 8.21 · 10^–15. The complex obeys Beer's law from 0.4 to 16 ppm of iron and the optimum concentration range is 1 to 8 ppm, with a relative analysis error of 2.3% per 1% absolute photometric error.

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Zusammenfassung Chelidamsäure bildet mit Eisen beiph 5,8–8,5 einen Komplex, der bei 460 nm ein Absorptionsmaximum aufweist. Das Verhältnis Metall: Reagens beträgt 13, die Instabilitätskonstante etwa 8,21 · 10^–15 Das Beersche Gesetz wird im Bereich von 0,4–16 ppm befolgt, der optimale Konzentrationsbereich liegt bei 1–8 ppm. Der relative Fehler beträgt 2,3% je 1% absoluten photometrischen Fehler.

     

Extraction of vanadium(V) chelates with N-benzohydroxamic acid (BHA) and ammonium thiocyanate and its application in steel and rock analyses

A mixed-ligand complex of vanadium(V) with N-benzohydroxamic acid and thiocyanate formed at various acidities can be extracted into methyl isobutyl ketone, and used for photometric determination of trace amounts of vanadium in materials such as alloy steels and rocks. The absorption maximum of the violet mixed-ligand complex is at 535 nm. The values for the simple complex are 505 nm and molar absorptivity 7.4 x 10(3)l.mole(-1).cm(-1).