Knowledge Bank

The pure rotational spectrum of 1,1-difluorocyanomethyl radical, CF$2$CN, was measured between 7.0 and 26.5 GHz using a Fabry-Perot cavity Fourier transform microwave (FP-FTMW) spectrometer. The $a$-type (K = 0, 1, 2) paramagnetic transitions were observed and assigned. The spectroscopic constants of CF$2$CN were fit by Pickett$\mathrm{<mrow\; data-mjx-texclass="ORD">,</mrow>}$s SPFIT suite of programs. The experimentally determined rotational constants are: A$0$ = 11010.58(1) MHz, B$0$ = 4081.6917(1) MHz, and C$0$ = 2989.9589(1) MHz. These constants are in a good agreement with the predicted values from density functional theory (DFT) calculation, UB3LYP/aug-cc-pVQZ. The inertial defect, $\Delta$ = -0.69 amu\AA$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$, indicates that CF$2$CN has a non-planar geometry. This is not the case in its isoelectronic analog, 1,1-difluoropropargyl, CF$2$CCH } \textbf{125}, 054309, (2006)}.