Knowledge Bank

Microwave and radiofrequency spectra have been obtained for the complexes of NCCN with itself, with $NH3$ and with $H2O$. All three systems are T--shaped with the heavy atoms in a $C2v$ arrangement and all yield spectra perturbed by internal motion. The $NH3$ subunit in $NH3-NCCN$ exhibits nearly free internal rotation with respect to the NCCN framework, whereas the $H2O$ subunit in $H2O-NCCN$ has a moderate torsional barrier. In (NCCN)$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$ the rotational spectrum appears to be perturbed by a low-frequency bending vibration, probably the vibration associated with the inversion tunnelling observed in $(HCCH)2$. $NH3-NCCN$ has a dipole moment of 1.06D with a 3.063{\AA} distance between the bonded nitrogen and the cyanogen center--of--mass. In $(NCCN)2$ this distance is 3.142{\AA} and the dipole moment 0.420D