Orellana W, Stephens SL, Pringle WC, Groner P, Novick SE, Cooke SA. Torsional splitting and the four-fold barrier to internal rotation: The rotational spectra of vinylsulfur pentafluoride.
J Chem Phys 2018;
149:144304. [PMID:
30316255 DOI:
10.1063/1.5050021]
[Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Vinylsulfur pentafluoride (VSPF), a molecule with a four-fold internal rotor, -SF4, has been studied with high resolution Fourier transform microwave spectroscopy. We believe that this is the first report of resolved four-fold internal rotation. As such, we have presented the tools needed to understand and analyze such a problem. These include debugging the ERHAM computer program necessary to fit the spectra and the free rotor to high barrier correlation diagram necessary to understand the torsional states of the four-fold rotor. The A, E, and B torsional state rotational transitions are well resolved and assigned. Spectroscopic transitions of four isotopologues of VSPF, H2C=CH-SF5, the normal isotopologue, and the singly substituted 34S and 13C isotopologues were measured and assigned. Contrary to expectation, the A torsional state could not be fit with only a semi-rigid Hamiltonian. The barrier to internal rotation, V 4, is found to be 227 cm-1. Ab initio calculations at the MP2 aug-cc-pVQZ level of theory and basis set were performed and the results of this calculation are compared to our experimental results.
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