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81.
82.
S. F. Baranovskii P. A. Bolotin M. P. Evstigneev 《Journal of Applied Spectroscopy》2006,73(2):171-177
We have studied self-association of aromatic molecules of the thiazine dye methylene blue in aqueous solution, using a dimer
model. We have determined the dimerization equilibrium constant for the dye molecules KD = 3900 ± 800 M−1 at T = 293 K. We have decomposed the experimental spectrum into dimer and monomer components. Using the ratio of the molar
absorption coefficients for two absorption bands of the dimer spectrum, we obtained the “average” value of the angle between
the electronic transition moments of the molecules in the dimers, α = 48°.
We have studied heteroassociation of methylene blue (MB) and 1,3,7-trimethylxanthine (caffeine) molecules in aqueous solution.
We have calculated the heteroassociation constant as 200 ± 34 M−1. We conclude that heteroassociation of methylene blue and caffeine molecules leads to a lower effective dye concentration
in solution, which hypothetically may affect its biological activity.
We have determined the values of the Gibbs free energy, the enthalpy, and the entropy for dimerization of methylene blue molecules:
ΔG293 = −(20 ± 3) kJ/mol, ΔH = −(25 ± 9) kJ/mol, Δ S293 = −(17 ± 6) J/mol·K; and for methylene blue-caffeine heteroassociation: ΔG293 = −(13 ± 3) kJ/mol, ΔH = −(14 ± 10) kJ/mol, ΔS293 = −(2.4 ± 0.2) J/mol·K, respectively. We have shown that the methylene blue aggregates and the heteroassociates with caffeine
are predominantly stabilized by dispersion interactions between the chromophore molecules in the associates.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 158–163, March–April, 2006. 相似文献
83.
84.
We have used UV and visible spectrophotometry to study self-association of aromatic riboflavin molecules (RFN, vitamin B2, 7,8-dimethyl-10-N-(1′-D-ribityl)isoalloxazine) in aqueous solution (pH 6.86) at T = 298 K, using a dimer model. We have
determined the equilibrium dimerization constant for riboflavin, KdB = 125 ± 40 M−1. We have studied heteroassociation in the system of molecules of 7,8-dimethyl-10-ribitylisoalloxazine with 1,3,7-trimethylxanthine
(caffeine) and sodium salicylate (NAS) in aqueous solution (pH 6.86; T = 298 K). We have determined the heteroassociation
constants for RFN-NAS and RFN-caffeine molecules in the absence and in the presence of urea in solutions using a modified
Benesi-Hildebrand equation: 25 ± 4, 17 ± 3, and 74 ± 11, 53 ± 7 M−1 respectively. We have determined the dimerization constants for NAS (2.7 ± 0.5 M−1) and caffeine (17.0 ± 1.5 M−1). We conclude that heteroassociation of the aromatic molecules leads to a lower effective riboflavin concentration in solution,
and the presence of urea in mixed solutions leads to an decrease in the complexation constants for the RFN-NAS and RFN-caffeine
systems.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 2, pp. 188–194, March–April, 2007. 相似文献
85.
86.
Linear orientational defects (2π and π walls) in freely suspended thin smectic C films exposed to a magnetic field were studied. The bend and splay elastic constants, as well as the orientational viscosity of a two-dimensional c-director field, were determined. It was established that a change in the polar and azimuthal angles of magnetic-field orientation in a sample cardinally transforms the wall structure. This is caused by the anisotropy of orientational elasticity of the c director. 相似文献
87.
E. B. Sveshnikova P. A. Shakhverdov T. A. Shakhverdov V. E. Lanin R. U. Safina B. M. Bolotin V. L. Ermolaev 《Optics and Spectroscopy》2003,95(6):898-907
The luminescence decay times τlum of the complexes of the ions Tb(III), Eu(III), Sm(III), Dy(III), and Yb(III) with dipicolinic acid (DPA) dissolved in protonated and deuterated water, methanol, and dimethyl sulfoxide are measured. The values of τlum for crystals H3[Ln(DPA)3]·nH2O and their aqueous solutions coincide, which points to the identity of the environment in the nearest spheres of an ion in both cases. A comparison of τlum of solutions of the complexes in H2O and D2O, as well as in CH3OH, CH3OD, CD3OD, DMSO-h 6, and DMSO-d 6 shows that the molecular groups in the second and third spheres of an ion, exhibiting high-frequency vibrations, have a noticeable effect on the rate constants of nonradiative transitions k nr in the ion. From this comparison, some inferences on the structure of the solvate shell of the Ln(DPA) 3 3? complexes in the solvents used are made. The contributions to k nr of Eu(III), Tb(III), Sm(III), Dy(III), Nd(III), and Yb(III) made by OH and CH groups located at different distances from the ion are estimated. It is demonstrated that the dependence of k nr on the distance to the OH and CH groups is steeper for the Eu(III) and Tb(III) ions than for the remaining ions. 相似文献
88.
By applying perturbation theory to the reciprocal of the nuclear charge (1/Z), the spectra of a series of oxygen-like ions (having configurations of the 1s22s22pn, 1s22s2pn+1, 1s22pn+2, n =4 type) are calculated. The results of the calculation are compared with existing experimental data. The difference between the theoretical and experimental energies of the terms is 0.1–1%. 相似文献
89.
90.
Poponova R. V. Bolotin B. M. Zeryukina L. S. Safina R. U. 《Chemistry of Heterocyclic Compounds》1977,13(5):494-496
Water is split out to form 2-phenyl-4H-3,1-benzoxazin-4-one when N-benzoylanthranilic acid is heated. A mass spectrometric study of O18-labeled N-benzoylanthranilic acid and the product of its thermal cyclodehydration showed that the oxygen atoms of the carboxyl and benzoyl groups participate equally probably in splitting out of water.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 614–615, May, 1977. 相似文献