Nitrogen-14 and sodium-23 nuclear magnetic resonance of sodium and potassium cyanide

Abstract

The temperature dependence of the spin‐lattice relaxation time of nitrogen‐14 in the cubic phases of NaCN and KCN yields the correlation time τ₂ and the activation energy ΔE_R of the reorientational motion of the CN⁻ ion. For NaCN, ${\mathrm{\Delta \; E}}_R\text{= 1.41± 0.20\hspace{0.17em}}{\mathrm{kcal\; mole}}^{\text{−1}}$ and ${\tau }_2{\text{= 1.2× 10}}^{\text{−10}}\hspace{0.17em}\sec$ at 300°K; for $\mathrm{KCN}{\mathrm{\hspace{0.17em}\Delta \; E}}_R\text{= 0.50± 0.25\hspace{0.17em}}{\mathrm{kcal\; mole}}^{\text{−1}}$ and ${\tau }_2{\text{= 2.3× 10}}^{\text{−10}}\hspace{0.17em}\sec$ at 300°K. Previous carbon‐13 relaxation data of Fukushima on KCN are reinterpreted in terms of the spin‐rotation interaction to yield the spin‐rotational correlation time τ₁. The product of τ₁ and τ₂ does not obey the Hubbard relationship, demonstrating that the motion of the cyanide ion in the cubic phase of KCN is not simply small step rotational diffusion over a sphere. Sodium‐23 relaxation times (T₁) in the cubic phase of NaCN were measured over the temperature range 285–435°K. The T₁ data exhibit an Arrhenius behavior with an activation energy of $\text{1.51± 0.20\hspace{0.17em}}{\mathrm{kcal\; mole}}^{\text{−1}}$ . Sodium‐23 NMR has been observed in the orthorhombic phase of NaCN, and the quadrupolar coupling constant ${\mathrm{(e}}^2{\mathrm{q\hspace{0.17em}Q}}_n\text{/h= 1.28± 0.06\hspace{0.17em}}\mathrm{MHz})$ and asymmetry parameter $\text{(η = 0.37± 0.07)}$ have been measured at 263°K. Nitrogen‐14 nuclear quadrupole resonance has been observed in the monoclinic phase of NaCN from 5 to 110°K. At 0°K, e²q Q_n/h = 4.004 MHz and η = 0.097 for nitrogen‐14 in the CN molecule‐ion.