VIBRONIC SPECTROSCOPY OF HETERO DIHALO-BENZYL RADICALS GENERATED BY CORONA DISCHARGE : JET-COOLED CHLOROFLUOROBENZYL RADICALS

Lee, Sang

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Description

Title

VIBRONIC SPECTROSCOPY OF HETERO DIHALO-BENZYL RADICALS GENERATED BY CORONA DISCHARGE : JET-COOLED CHLOROFLUOROBENZYL RADICALS

Author(s)

Lee, Sang

Contributor(s)

Yoon, Young

Issue Date

23-Jun-15

Keyword(s)

Radicals

Abstract

"The technique of corona excited supersonic jet expansion coupled with a pinhole-type glass nozzle was applied to vibronic spectroscopy of jet-cooled chlorofluorobenzyl radicals for the vibronic assignments and measurements of electronic energies of the D$_1$ $rightarrow$ D$_0$ transition. The vibronic emission spectra were recorded with a long-path monochromator in the visible region. The 2,3-, 2,4-,footnote{C.~S.~Huh, Y.~W.~Yoon, and S.~K.~Lee, textit{J. Chem.~Phys.} underline{textbf{136}}, 174306 (2012).} and 2,5-footnote{S.~Y.~Chae, Y.~W.~Yoon, and S.~K.~Lee, textit{Chem.~Phys.~Lett.} underline{textbf{612}}, 134 (2014).}chlorofluorobenzyl radicals were generated by corona discharge of corresponding precursor molecules, chlorofluorotoluenes seeded in a large amount of helium carrier gas. The emission spectra show the vibronic bands originating from two benzyl-type radicals, chlorofluorobenzyl and fluorobenzyl benzyl radicals, in which fluorobenzyl radicals were obtained by displacement of Cl by H atom produced by the dissociation of methyl C-H bond. From an analysis of the spectra observed, we could determine the electronic energies in D$_1$ $rightarrow$ D$_0$ transition and vibrational mode frequencies at the D$_0$ state of chlorofluorobenzyl radicals which show the origin band of the electronic transition to be shifted to red region, comparing with the parental benzyl radical. The red-shift is highly sensitive to the number, position, and kind of substituents in chlorofluorobenzyl radicals. From the quantitative analysis of the red-shift, it has been found that the additivity rule, discovered recently by Lee group predicts the observation very well. In addition, the negligible contribution of the substituent at the 4-position, the nodal point of the H\""{u}ckel�s molecular orbital theory, can be well describes by the disconnection of substituent from molecular plane of the benzene ring available for delocalized $pi$ electrons. In this presentation, I will discuss the spectroscopic observation of new chlorofluorobenzyl radicals and substituent effect on electronic transition energy which is useful for identification of isomeric substituted benzyl radicals."

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

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