Knowledge Bank

The structures of $(OCS)2CO2$ and $(OCS)3$ have been determined from rotational spectra obtained using a pulsed nozzle Fourier transform spectrometer. The two trimers have a barrel like monomer arrangement commonly seen in similar complexes. In $(OCS)2CO2$, the two OCS units have an anti-parallel arrangement, like the OCS dimer, but twisted from planarity by $34\circ$. The$ CO_{2}$ straddles both of them in an approximately parallel orientation. In $(OCS)3$, two of the OCS molecules are again nearly anti-parallel with the third OCS straddling them. Seven isotopic species were assigned for $(OCS)2CO2$. Two isotopic species were assigned for $(OCS)3$, to supplement the normal species data previously $reported.a$ The dipole moments of the trimers are consistent with the derived structures. Comparisons of the structures with results from a semi-empirical model including electrostatic, dispersion and repulsive terms will be presented.