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 ΔER of the reorientational motion of the CN− ion. For NaCN, Δ ER= 1.41± 0.20 kcal mole−1 and τ2= 1.2× 10−10 sec at 300°K; for KCN Δ ER= 0.50± 0.25 kcal mole−1 and τ2= 2.3× 10−10 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 1.51± 0.20 kcal mole−1. Sodium-23 NMR has been observed in the orthorhombic phase of NaCN, and the quadrupolar coupling constant (e2q Qn/h= 1.28± 0.06 MHz) and asymmetry parameter (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 Qn/h = 4.004 MHz and η = 0.097 for nitrogen-14 in the CN molecule-ion.