Microwave spectra, molecular geometries and barriers to internal rotation in complexes of Ar...C5H7N2 and H2O...C5H7N2 (where C5H7N2 is 1-, 2-, 4- or 5-methylimidazole)
Walker, Nick
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https://hdl.handle.net/2142/104439
Description
Title
Microwave spectra, molecular geometries and barriers to internal rotation in complexes of Ar...C5H7N2 and H2O...C5H7N2 (where C5H7N2 is 1-, 2-, 4- or 5-methylimidazole)
Author(s)
Walker, Nick
Contributor(s)
Heitkämper, Juliane
Medcraft, Chris
Gougoula, Eva
Issue Date
2019-06-17
Keyword(s)
Non-covalent interactions
Abstract
Experiments performed to observe the broadband microwave spectra of 1-methylimidazole, 2-methylimidazole, 4-methylimidazole and 5-methylimidazole also yielded the spectra of molecular complexes containing these molecules. The complexes were generated through laser vaporisation of a solid target rod in the presence of a gas sample undergoing supersonic expansion and containing Ar and H$_2$O precursors. Spectra have thus been recorded for a series of structural isomers of Ar$\cdots$C$_{5}$H$_{7}$N$_{2}$ and H$_{2}$O$\cdots$C$_{5}$H$_{7}$N$_{2}$ where C$_{5}$H$_{7}$N$_{2}$ is an isomer of methylimidazole. Rotational constants, {\it{B}}$_{0}$, centrifugal distortion constants, {\it{D}}$_{\it{J}}$, and nuclear quadrupole coupling constants, $\chi_{aa}$(N) and $\chi_{bb}$(N)-$\chi_{cc}$(N) have been determined through assignment of the observed rotational spectra. For each of the structural isomers identified, it will be shown that the argon atom of Ar$\cdots$C$_{5}$H$_{7}$N$_{2}$ coordinates to $\pi$ electrons of the aromatic ring of methylimidazole. The water molecule in H$_{2}$O$\cdots$C$_{5}$H$_{7}$N$_{2}$ binds to the pyridinic nitrogen atom of the methylimidazole sub-unit. For each complex, the barrier to internal rotation, ${\it{V}}_3$, of the methyl group has been determined.
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