Rotations of linear triatomic anions in aqueous solution by nuclear magnetic resonance spectroscopy

Abstract

The temperature dependence of nitrogen-14 nuclear magnetic resonance (nmr) spin-lattice relaxation times (T1) for dilute aqueous solutions of the linear triatomic anions, SeCN−, SCN−, OCN−, and N3−, is investigated in the temperature range 3–80 °C. These nmr relaxation times (T1) yield rotational correlation times, τ2R, for the reorientation of the C∞ symmetry axis in these anions. The observed nonlinear dependence of log T1(14N) on temperature suggests that the rotations of the anions are coupled to the transport properties of water. For the thiocyanate anion the nmr correlation times are compared with those obtained previously from Raman spectroscopic data and Rayleigh scattering results. 17O T2 and I4N T1measurements for the NCO− anion are used along with abinitio calculations to estimate the 17O nuclear quadrupolar coupling constant in this ion.