# $n\pi^{*}$ TRANSITIONS IN SULFUR DERIVATIVES OF TETRAMETHYL-1,3-CYCLOBUTANEDIONE

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 Title: $n\pi^{*}$ TRANSITIONS IN SULFUR DERIVATIVES OF TETRAMETHYL-1,3-CYCLOBUTANEDIONE Creators: Crawley, J.; Gordon, R. D.; Gransden, S. E.; Marion, R. Issue Date: 1980 Publisher: Ohio State University Abstract: The polarized low-temperature crystal absorption spectra of tetramethyl-1,3-cyclobutanedithione–$h_{12}$ and $-d_{12}$ (II) have been measured in the visible region, and $n\pi^{*}$ excited states identified as follows :$^{3}A_{u}$ with origin $(h_{12}/d_{12})$ at 16829/16836 $cm^{-1};\ ^{1}A_{u}$ and $^{1}B_{1g}$ with nearly degenerate origins near $18000 cm^{-1}$ and probably $^{1}A_{u}$ and $^{1}B_{1g}$ near $19500 cm^{-1}$. The singlet excited states lie close together and perturb each other strongly. Isotope shifts, and anologies to the spectrum of the dione (I)$^{1}$, played an important part in the analysis. As in the dione (I), CH/CD stretching vibrations in the peripheral methyl are groups are active in intensity borrowing, and the effects of excitation are delocalized over the entire molecule. Preliminary results for the $C_{2v}$ molecule (III) will also be presented. [Figure] Description: $^{1}$R. D. Gordon, M. Caris, and D. G. Newman, J. Mol. Spectrosc. 60, 130-149 (1976). Author Institution: URI: http://hdl.handle.net/1811/11166 Other Identifiers: 1980-FC-7