Neither of the two names describes HNCN well. In fact, the molecule is best described as being between cyanoamidogen (HN–C≡N) and iminomethyleneamidogen (HN=C=N). The rotational spectrum was recorded between 260 and 400 GHz by
(1) S. Yamamoto and S. Saito, 1994, J. Chem. Phys. 101, 10350.
No hyperfine structure (HFS) splitting was resolved, but fine structure splitting was resolved throughout. HFS from the ¹H and the two different ¹⁴N nuclei will be resolvable in the microwave region; in the 3 mm region, it will be essentially collapsed for K_a = 0 and 1.
Predictions with uncertainties larger than 0.3 MHz should be viewed with caution.
The ab initio dipole moment components were calculated by
(2) H. S. P. Müller, 2012, unpublished.
NOTE: The molecule has a sizable b dipole moment component of slightly more than 1 D. However, the corresponding transitions can not be predicted with confidence at present.