The microwave spectrum of the difluorocyanomethyl radical, ĊF2CN.

[Display omitted] • Questioning the planarity of the open shell difluorocyanomethyl radical. • Complex hyperfine structures observed in the microwave spectrum. • Spin-rotation coupling, nuclear quadrupole coupling, and Fermi contact interactions. The pure rotational spectrum of the open shell difluorocyanomethyl radical, ĊF 2 CN, has been measured using two Balle-Flygare-type cavity Fourier-Transform-Microwave (FTMW) spectrometers both equipped with pulsed discharge nozzles. A total of 156 transitions (from N = 1 – 0 to 6 – 5, and K a = 0, 1, 2, 3) in the electronic ground state were observed between 6.5 GHz and 38.4 GHz with a typical linewidth of ∼5 kHz full-width-half-maximum. A Hamiltonian that included semi-rigid rotor, spin-rotation, and nuclear hyperfine parameters was fit to the observed data set and these parameters have been interpreted and compared to similar radicals. Excellent agreement between experimental and uB3LYP/aug-cc-pVQZ calculated rotational constants, the experimental inertial defect, −0.6858(2) uÅ2, and the failure of a coupling scheme in which the fluorine nuclei are treated as identical and related by a C 2v symmetry axis combine to indicate a nonplanar structure for the ĊF 2 CN radical. [ABSTRACT FROM AUTHOR]