Please use this identifier to cite or link to this item:

Show simple item record

Files Size Format View
1997-RD-10.jpg 179.9Kb JPEG image Thumbnail of Ar MATRIX TRAPPING SITES FOR CYCLOBUTADIENE

dc.creator Redington, R. L. en_US 2006-06-15T15:42:49Z 2006-06-15T15:42:49Z 1997 en_US
dc.identifier 1997-RD-10 en_US
dc.description $^{a}$A. M. Orendt et al., J. Am. Chem. Soc. 110, 2648 (1991) $^{b}$B. R. Arnold and J. Michl, J. Phys. Chem. 97, 13348 (1993), $^{c}$B. R. Arnold et al., J. Am. Chem. Soc. 113, 692 (1991). $^{d}$P. Carsky and J. Michl. Theor. Chim. Acta 84, 125 (1992) en_US
dc.description Author Institution: Department of Chemistry and Biochemistry, Texas Tech University en_US
dc.description.abstract The possibility of quantum mechanical tunneling by cyclobutadiene (CB) remains of interest, and the present MO computations relating to Ar matrix trapping sites of CB were motivated by the spectral observations of Michl et al. Their IR and ${^{13}}$CMR $spectra^{a,b}$ suggest that automerization occurs at a rate faster than $10^{3} s^{-1}$ in the Ar-isolated CB system, while they found only one transition, rather than widely spaced doublet, for the automerization mode in the $Raman^{c,d}$ spectrum. The present MO computations consider CB:$Ar_{n}$ clusters based on ccp and hcp Ar lattice fragments at the MP2/6-311++(2d, 2p) level of MO theory. The results suggest: a) the feasibility for energy offsets of the asymmetrical double-minimum PES of CB that are greater than $35 cm^{-1}$ in some Ar trapping sites -- i.e. larger than needed to $depopulate^{c,d}$ the upper Raman doublet component; and b) that the global PES for the Ar/CB matrix system can achieve symmetrical double-minimum character when modest trapping site rearrangement accompanies the CB automerization. The observation of what may be very slow tunneling by Ar-isolated CB in comparison with estimated free molecule rates is then explainable in terms of the adiabatically separated fast CB automerization mode and slow trapping site adjustment. en_US
dc.format.extent 184309 bytes
dc.format.mimetype image/jpeg
dc.language.iso English en_US
dc.publisher Ohio State University en_US
dc.type article en_US