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161.
Conformational studies on some p-dimethylamino β-aza and β-aza (with respect to the dimethylamino phenyl ring) styryl dyes derived from quinoline-4, quinoline-2, pyridine-4, pyridine-2, and benzothiazole-2 have been carried out using the quantum mechanical PCILO (perturbative configuration interaction using localized orbitals) method. These molecules may be considered as heterocyclic analogues of benzylidene anilines whose conformations have been studied extensively by both theoretical and experimental methods to explain the difference of their spectra from the isoelectronic benzylidene compounds. The results of the present studies show that the β-aza styryl dyes are nearly planar. In case of β-aza styryl dyes, although the phenyl ring is coplanar with the central atoms, there is a substantial twist of the heterocyclic ring. These results are explained in terms of CT -1 and CT -2 effects and are used as a possible explanation for the observed spectral and sensitization properties. 相似文献
162.
Summary Rate constants for the oxidation of thiosulphate by hexachloroplatinate(IV) have been measured. The kinetics of the oxidation of thiosulphate follow a second-order rate law, first order with respect to thiosulphate and first order with respect to platinum(IV). The influence of pH is small. The rates are found to depend on the nature and concentration of the cations and follow the order: Cs+>Rb+>K+>Na+>Li+. The activation parameters calculated from the temperature studies are: H=42.9 k J mol–1 and S=–102 JK–1 mol–1. A mechanism of the reaction in terms of intermediate formation of free radicals followed by the formation of tetrathionate is postulated to explain the kinetic behaviour. 相似文献
163.
Summary The products from the reaction oftrans-dioxobis(ethylenediamine)rhenium(V) halides with hydrogen halides have been investigated. Dilute (2M) and concentrated hydrochloric acid react with (ReO2en2)Cl in the cold to give ReO(OH)enCl2 and IRe(OH)2enCl2]Cl respectively, while with hot 6M HCl [ReOCl5]2– is formed. Dilute solutions of HX protonate [ReO2en2]X (X = Br and I) giving [ReO(OH)en2]X2 which are converted slowly into ReO(OH)enBr2 and [ReO(OH)en2](I3)2. Hot and concentrated solutions of HX reduce Rev in (ReO2en2 )X (X = Br and I) giving enH2(ReBr6) and ReI4en. The thermal decomposition of (ReO2en2)X (X = Cl, Br and I) has been studied by thermogravimetry and a polymeric compound, Re2O7en2, has been isolated by heating (ReO2en2)X at 200°. The compounds have been characterised by molecular conductivities, magnetic susceptibility and i.r. spectra. 相似文献
164.
165.
166.
Summary Dipole polarizability estimates at have been calculated for the 2p and 3p open-shell negative ions in their ground and valence excited states. To complete the sequence such estimates for F– and Cl– in their ground1
S state have also been made. Single configuration based linear response theory has been adopted presently with a view to study the effect of RPA-type correlations on the polarizabilities of such systems. For the 3p open-shell systems the innermost 1s core has been kept frozen. Most of the results are reported for the first time. Agreement with existing data, wherever available, is reasonable. The convergence of the polarizability estimates towards basis sets has been studied. 相似文献
167.
168.
N-Benzoyl-o-tolylhydroxylamine is shown to provide a virtually specific reagent for the spectrophotometric determination of vanadium. The reddish-violet complex formed with the reagent in 4–8 N hydrochloric acid after extraction with chloroform shows absorption maxima at 510 mm, and obeyes Beer's law from 0.5 to 10 μg with an optimum range of 2–10 μg; the percent relative error is 2.7. The sensitivity is 0.0108 μg V/cm2. The complex contains the metal and the reagent in a ratio of 1:2 and the dissociation constant is of the order of 10-9. 相似文献
169.
M. K. Das N. Ramamoorthy B. R. Sarkar R. S. Mani 《Journal of Radioanalytical and Nuclear Chemistry》1987,111(2):469-475
We have studied the feasibility of producing57Co (271.3 d) via the55Mn(, 2n)57Co reaction (55Mn–100%). The thick target yield of57Co in the 28 to 18 MeV energy region was measured as 3.87 Ci/Ah. However, the proximity and overlap of the excitation functions for (, n), (, 2n) and (, 3n) reactions on55Mn are such that the production of pure57Co in high yields free of58Co (70.8 d) and56Co (78.8 d) has not been feasible. We have also studied a new method for ancillary production of57Co via the reactions58Ni(, p)57Co and
during the course of producing62Zn by60Ni(, 2n)62Zn reaction. In this case the yield of57Co of reasonable purity has been up to 1 Ci/Ah. 相似文献
170.
Nigamananda Das 《Transition Metal Chemistry》1993,18(4):372-376
Summary The kinetics of reversible complexation of Ni(OH2)
inf6
sup2+
with oxygen-bonded glycinatocobalt(III) substrates N4-Co(glyH)gly2+ [N4 = (en)2 or trien; glyH = H3N+CH2-COO–] have been investigated by the stopped-flow technique in the 20–35° C range, at pH = 6.08–6.82 and I = 0.3 mol dm–3. The formation of N4Co(glyH)glyNi4+ occurred via the reaction of Ni(OH2)
inf6
sup2+
with the deprotonated form of the cobalt(III) substrates, N4Co-(glyH)gly2+. The rate and activation parameters for the formation and dissociation of the binuclear species are reported. The formation rate constants k
f (at 25° C), activation enthalpy and entropy H
, S
for N4Co-(glyH)glyNi4+ are 320±49, 341 ± 52dm3mol–1 s–1, 78 ± 7, 79 ± 5 kJmol–1 and 64 ± 24, 69 ± 18 JK–1 mol–1 for the ethylenediamine and triethylenetetraminecobalt(III) substrates, respectively. This result indicates that the rate and activation parameters are virtually independent of the nature of N4 moities, which strongly suggests that the formation of mono-bonded species occurs via entry of one of the pendant NH2 groups into the coordination sphere of nickel(II) via a rate-limiting Ni-OH2 bond dissociation mechanism (Id). The binuclear species exist in dynamic equilibrium between the monodentate and chelated forms, with the chelate form predominating. The low values of spontaneous dissociation rate constant for the binuclear species (k
r- 0.095–1 at 25° C) in comparison with the high values of dissociation rate constants of monodentate nickel(II) complexes reported in the literature also support the chelate nature of the binuclear species. 相似文献