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dc.creatorHaas, Y.en_US
dc.creatorZilberg, S.en_US
dc.date.accessioned2007-11-20T17:13:13Z
dc.date.available2007-11-20T17:13:13Z
dc.date.issued1995en_US
dc.identifier1995-TE-09en_US
dc.identifier.urihttp://hdl.handle.net/1811/29788
dc.descriptionY. Haas and S. Zilberg, J. Am. Chem. Soc., submitted.en_US
dc.descriptionAuthor Institution: The Hebrew University of Jerusalem, Jerusalem, Israel 91904en_US
dc.description.abstractThe $\nu_{14}(b_{2u})$ mode of benzene undergoes a significant frequency increase upon excitation of the molecule from the ground electronic state. $S_{0}(^{1}A_{1g})$ to the first electronically excited state $S_{1}(^{1}B_{2q})$. It is the only mode that exhibits this pronounced increase, most other modes show a modest frequency decrease, as expected for the weakend bonding in the excited state. An ab-initio calculation shows that this change involves a considerable increase in the force constant and in the reduced mass of the mode, which becomes essentially a pure carbon atom mode in $S_{1}$. This change is in line with the notion [Shaik, Hiberty. Ohanessian and Lefour, J. Phys. Chem., 92, 5086 (1988)] that the $D_{2u}$ symmetry of the molecule is due to $\sigma$-bonding, and that the $\pi$-electrons actually tend to distort the molecule to a Kekul\'{e} form. According to the theory of Shaik and Hiberty, promotion of a $\pi$ electron to an antibonding orbital is expected to reduce the $\pi$-distortivity power and thus helps to reveal more clearly the influence of the $\sigma$-potential on the Kekule type $b_{2u}$ mode. A similar effect is found to take place for the lowest lying $B_{2u}$ state of other aromatic hydrocarbons, even if they are not $S_{1}$, as shown for anthracene by an ab-initio calculation. The $A_{g}$ and $B_{2u}$ states may be considered as arising primarily from the two Kekule valence bond structures by a positive and negative combinations, respectively.en_US
dc.format.extent68992 bytes
dc.format.mimetypeimage/jpeg
dc.language.isoEnglishen_US
dc.publisherOhio State Universityen_US
dc.titleTHE $\nu 14(b2u)$ MODE OF BENZENE IN SO AND SI: DO THE II ELECTRONS TEND TO DISTORT THE MOLECULE TO THE KEKULE FORM?en_US
dc.typearticleen_US


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