Sodium-23 nuclear magnetic resonance on sodium borate solutions. Anion, solvent, and viscosity effects

Alkali N.M.R. experiments on the radical ion pairs of biphenyl and fluorenone

“…The latter effect is visible in the case of the LiBp and NaBp solutions, where at low temperatures a residual small variation of the hfsc is observed as a function of the solvent (figures 2, 4). Especially the effect of Tg and Ttg on Aa has been noted previously [17] (see figure 4) and probably points to a special ion pair structure. This will be discussed more fully in a subsequent paper dealing with a line width analysis, in which it is shown that the increase in alkali line width going to higher temperatures can be ascribed to enhanced anisotropic dipolar interaction.…”

“…~aNa N.M.R. studies on solutions of sodium tetrahydroborate (NaBH4) and tetraphenylborate (NaB(Ph)4) have demonstrated that the variation of a-%q as a function of the same solvents as used in the present study are minor [17]. It also appeared that a-%q was positive and either remained constant or increased with temperature, which in our case would result in a negative temperature coefficient of the hfsc (see equation (3)).…”

“…Also, measured or estimated values of aaq are given. In nearly all cases reported in the literature the variation of resulted from a variation of anion and solvent ; the influence of the temperature has not been investigated extensively [17]. The most thoroughly studied cases seem to be the solutions of sodium salts ; the quoted range for Na is therefore probably the relatively largest one.…”

Glymes as versatile solvents for chemical reactions and processes: from the laboratory to industry

“…Takaki and Smid 124 titrated difluorenylbarium with glymes and crown ethers in THF at 25 °C under vacuum to examine the formation of ion pair-glyme and – crown ether complexes, and found that 1:1 complexes are formed for difluorenylbarium with mono- and dibenzo-18-crown-6 as well as with glyme-7 and glyme-9 while a 2:l crown-ion pair complex is formed for monobenzo-15-crown-5. Canters 58 analyzed the shift and line widths in 23 Na NMR spectra of glyme solutions of NaBPh 4 and NaBH 4 as a function of temperature; it was found that the transition from solvent separated to contact ion pairs and the type of anions show a considerable impact on the position of alkali NMR signals, while the line width is typically a linear function of the viscosity of pure solvent divided by absolute temperature. Detellier and Laszlo 125 observed the tetracoordination of Na + cation when studying the 23 Na NMR chemical shifts for NaClO 4 in binary mixtures of glyme and tetrahydrofurfuryl alcohol.…”

Electron spin distribution and molecular dynamics of aromatic hydrocarbon radical anions studied by1H and2D N.M.R.

“…Assuming that the viscosities of both solvent [36] and solution have the same temperature coefficient [37], one predicts from % at 30~ in a 1.0 M solution (56 + 8 ps) the measured re's at other temperatures and concentrations within 1 ps. For a 1.2 M NaAn-THF sample at 30~ one predicts % equal to 47 • 7 ps, indicating a more efficient electron spin relaxation in the NaAn sample compared to the LiAn mixed sample (see table 7) [23,28].…”