Nitrogen-14 Quadrupole Coupling Constants in Propanedinitrile, CH2(CN)2, by Microwave Spectroscopy

Abstract

Nitrogen-14 quadrupole hyperfine structure has been resolved in the microwave spectrum of propanedinitrile, CH2(CN)2. Measurements between 5 and 30 GHz by Fourier transform and Stark modulation spectroscopy have been analysed. The general matrix elements for nuclear quadrupole interaction in molecules containing two equivalent coupling nuclei have been derived as simple formulae. The quadrupole coupling constants determined for the inertial axis system of CH2(CN)2 are χaa = - 2.368(28) MHz, χbb = 0.318(20) MHz, and χcc = 2.050(20) MHz. These values are used to establish that the electric field gradient tensor at nitrogen is cylindrically symmetric about the C≡N bond with a value of χCN = - 4.09(4) MHz, close to values found for other organic cyanides.