Peculiarities of Quadrupolar Relaxation in Electrolyte Solutions

Abstract

Peculiarities of quadrupolar relaxation in electrolyte solutions were established via comparison of the data obtained from proton and deuteron resonances. It has been shown that quadrupole coupling constants (QCC) of deuterons depend not only on internal electron structure of molecule or ion, but on solution structure as well. To interpret the experimental results quantumchemical calculations of QCC of deuterons in different molecular complexes simulating different solution substructures were carried out. Density functional theory (DFT) method with hybrid B3LYP functional was used for all calculations.

Acidic Centers on the Surface of a Crystalline α-Sn(IV) Phosphate Characterized by the Solid-State 1H, 2H, 31P, and 119Sn MAS NMR Techniques

“…It should be emphasized that the latter is also valid for the resonance at ∼5 to 6 ppm, which can be assigned to immobile water. The DQCC of the lowest field resonance is similar to D 3 O + in α-Zr phosphate (DQCC = 189 ± 8 kHz) and in crystalline D 3 O + C1O 4 – (DQCC = 169 kHz), while the static quadrupolar coupling constants for three deuterons in isolated ions D 3 O + were calculated to be 180, 183, and 202 kHz . Unfortunately, because of the wide spread of the quadrupolar patterns, the accurate 2 H T 1 time measurements were unsuccessful.…”

Hydronium Ions on the Surface of a Partially Hydrolyzed α-Zirconium Phosphate: Solid-State 2H and 31P MAS NMR Evidence

“…18 However, in contrast to the C Q constants of D 3 O + ions in crystalline D 3 O + C1O 4 − (169 kHz) 21 and D 3 O-Alu (17 kHz), 18 reduced by fast D 3 O + reorientations, the C Q value in 1-D 2 Oh/dr is larger (∼189 kHz) and rather closer to the static quadrupolar constants, obtained theoretically for an isolated D 3 O + ion as 247 kHz 25 or as 180, 183, and 202 kHz for three deuterons in isolated D 3 O + . 34 We explain the less mobility of D 3 O + ions and also sites ZrOD in the zirconium phosphate 1-D 2 Oh/dr by hydrogen bonding in Figure 4, which prevents intense motions of these sites. Here the two hydrogen-bonded deuterons of D 3 O + give the resonance at δ(iso) = ∼13 ppm, while the signal at 6.1 ppm can be assigned to the "free" deuterium of the hydronium ion.…”

“…Experimentally, they have been characterized in crystalline (H 3 O + )­Zr 2 (PO 4 ) 3 , p -toluenesulfonic acid monohydrate, and zeolite channels, in addition to the above-mentioned solid D 3 O + C1O 4 – and D 3 O-Alu . However, in contrast to the C Q constants of D 3 O + ions in crystalline D 3 O + C1O 4 – (169 kHz) and D 3 O-Alu (17 kHz), reduced by fast D 3 O + reorientations, the C Q value in 1-D 2 Oh/dr is larger (∼189 kHz) and rather closer to the static quadrupolar constants, obtained theoretically for an isolated D 3 O + ion as 247 kHz or as 180, 183, and 202 kHz for three deuterons in isolated D 3 O + . We explain the less mobility of D 3 O + ions and also sites ZrOD in the zirconium phosphate 1-D 2 Oh/dr by hydrogen bonding in Figure , which prevents intense motions of these sites.…”

“Hydration Shells” of CH2 Groups of ω-Amino Acids as Studied by Deuteron NMR Relaxation

“…Water molecules in aqueous solutions of organic molecules are distributed among various substructures of a solvent, which are characterized by different rotational correlation times τ c and quadrupole coupling constants χ. Quantum chemical calculations have however shown that the difference between the χ for bulk water and hydration shells of solute molecules is about 5–10%. ,, For example, Pavlova and Chizhik carried out accounting this difference for the precise calculation of rotational correlation times in the hydration shells of ions in electrolyte solutions . For hydration shells of organic molecules, there is some evidence that the change of τ c is considerably greater than 5–10% in comparison to τ c of bulk water. ,− ,− ,,− , Eventually, the variations in NMR relaxation rate R 1 are mainly caused by changes in rotational correlation times.…”