THE MICROWAVE SPECTRUM AND STRUCTURE OF THE PYRIDINE$\cdots$CO COMPLEX
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Date
1994
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Ohio State University
Abstract
The microwave spectra have been measured and assigned for 5 isotopic species of the pyridine $\ldots$ CO complex. The spectra contained no evidence for large amplitude motions, i.e., no perturbations nor splittings other than hyperfine were observed. The size of the centrifugal distortion constants also implied a relatively strongly bound complex. CO was expected to lie above the aromatic ring plane as was found for the diatomic monomer in benzene $\ldots$ CO, pyrrole $\ldots$ CO and benzene $\ldots N_{2}$. However, in pyridine $\ldots$ CO the CO is located in the ring plane of pyridine, the complex being planar ($\Delta_{o} \approx -0.76$ u {\AA}$^{2}). \Lambda_{0}$ and $\Lambda_{4}$ structures have been determined each yielding two possible structure for the complex, although one structure agrees better with the spectroscopic data than the other. Again we were surprised to discover that CO did not lay along the $C_{2}$ axis of pyridine. This was clearly indicated by the presence of two dipolar types of transitions in the spectra and from the structural analysis. The structure of the complex will be presented and a comparison with the benzene $\ldots CO_{1}$ pyrrole $\ldots $CO and furan $\ldots HCl$ complexes will be made.
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Author Institution: Department of Physics, Ohio State University; Laboratorium f\""{u}r Physikalische Chemie, Eidgen\""{o}ssische Technische Hoschschule