Theoretical investigation of 1,4-dioxane complexes with water in the <Emphasis Type="Italic">chair</Emphasis> conformation by semiempiric MNDO/PM3 method

The structure and relative stability of 1,4-dioxane-water, (Diox)_n·(H₂O )_m (n = 1, 2, m = 1–6), molecular complexes have been calculated by semiempirical MNDO/PM3 method. A considerable variety of (Diox)_n·(H₂O )_m isomeric structures was stated. The mean energy of O_Diox…H_W-O_W hydrogen bond in (Diox)_n·(H₂O)_m complexes formed by 1,4-dioxane molecules in the chair conformation amounts to ?2.293 ± 0.210 kcal/mol with the average bond length 2.797 0.015 Å.     

Magnetic relaxation characteristics of Gd(III) in N,N-dimethylformamide according to 1H and 14N NMR data

The solvation of Gd³⁺ is studied in N,N-dimethylformamide by ¹H and ¹⁴N NMR in the temperature range of 298–373 K.     

Solvation microdynamics of the Gd(3+) ion in 4-methyl-<Emphasis Type="Italic">N</Emphasis>-butylpyridinium tetrafluoroborate as probed by <Superscript>19</Superscript>F NMR and EPR

The solvation dynamics of the Gd(3+) ion in the ionic liquid 4-methyl-N-butylpyridinium tetrafluoroborate was studied by ¹⁹F NMR and EPR.     

Some structural peculiarities of formamide-water binary mixtures according to proton spin-spin relaxation data

The formamide-water system has been studied by the proton spin-spin relaxation method. The compositions of the resulting heterosolvates have been determined along with the stability constants on the mole fraction scale, and the relaxation efficiency coefficients.Original Russian Text Copyright © 2004 by I. V. Sukhno, V. Yu. Buzko, V. T. Panyushkin, and I. A. KovalevaTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 748–750, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

DFT study of the structural characteristics of the yttrium(3+) aqua ion

Density functional theory (DFT) using SVWN5, B3LYP, B3P86, O3LYP, B3PW91, B1LYP, B971, MPW1PW91, PBE1PBE, BHandH, and BHandHLYP density functionals was employed to study the structural characteristics of the Y(H₂O) ₈ ³⁺ yttrium aqua ion. The nonlocal hybrid GGA functionals show worse predictive ability in structural calculations of the Y(H₂O) ₈ ³⁺ aqua ion compared to the relatively simple combined functional BHandH and to the simplest SVWN5 functional in LSDA theory.     

Study of the structure and stability of aqua complexes Y(H2O) n 3+ (n = 1–10) by Ab initio methods

The structural and energetic characteristics of aqua complexes Y(H₂O) _n ³⁺ (n = 1–10) have been calculated by the ab initio RHF and MP2 methods.     

Complexation in the System Paramagnetic Ion (Tm3 +)-Diamagnetic Ion (Mg2 +)-Carboxylic Acid

The dependence of the NMR chemical shift in the system containing complexes of a paramagnetic cation PL and PL₂ on the concentration of a diamagnetic salt was simulated. The complexation in the system paramagnetic ion (Tm^{3 +})-diamagnetic ion (Mg^{2 +})-carboxylic acid (acetic, propionic, n-butyric) was studied experimentally. The effect of the second cation on the calculated complexation constants was detected.     

Different Complexation of Nd3+ and Sm3+ with L-Malic Acid

Complexation of Nd³⁺ and Sm³⁺ ions with L-malic acid (H₃Mal) in aqueous solutions (I = 0.1 mol/l KCl) was studied by pH-metric titration at the molar concentration ratios of H₃Mal : lanthanide equal to 1 : 2, 1 : 1, 2 : 1 in the pH range 2.8–9.5. Mathematical modeling of composite equilibrium processes was used to determine the compositions and stability constants of Nd(III) and Sm(III) L-malate complexes. It was found that in addition to the 1 : 1 and 1 : 2 complexes with different degree of deprotonation, the protonated L-malate complexes and hydroxo complexes of these metals were also formed. The Sm³⁺ and Nd³⁺ ions were established to behave differently during complexation with H₃Mal.     

The physicochemical characteristics of heteroassociates in the N,N-dimethylformamide-water system

The data on proton magnetic spin-spin relaxation, refractometry, acoustic spectroscopy, densimetry, and excess enthalpy of mixing of the N,N-dimethylformamide-water system are reviewed. The molar volumes, molar refractions, electronic polarizabilities, and isothermal compressibilities of heteroassociates formed in the N,N-dimethylformamide-water binary system were calculated.     

Characteristics of Heteroassociates in the System Dimethylformamide-Water,According to Data of <Superscript>1</Superscript>H NMR Relaxation,Refractometry, Densimetry,and Acoustic Spectroscopy

The dimethylformamide-water system was studied by proton spin-spin relaxation (296 K) and refractometry (298 K), and the results in combination with published densimetric data (293 K) and data on the sound velocities (293 K) were used to simulate the associative equilibria. A consistent scheme of heteroassociative equilibria in the dimethylformamide-water system was suggested. The compositions of the heteroassociates were determined, and their stability constants (in the mole fraction scale), relaxation efficiency coefficients, limiting refractive indices, limiting sound velocities, and limiting densities were calculated.