Molecular Structure And Chirality Determination From Pulsed-jet Fourier Transform Microwave Spectroscopy

Perez, Cristobal

Permalink

https://hdl.handle.net/2142/51188 Copy

Description

Title

Molecular Structure And Chirality Determination From Pulsed-jet Fourier Transform Microwave Spectroscopy

Author(s)

Perez, Cristobal

Contributor(s)

• Lehmann, Kevin
• Pate, Brooks
• Seifert, Nathan A.
• Evangelisti, Luca
• Lobsiger, Simon

Issue Date

2014-06-17

Keyword(s)

Instrument/Technique Demonstration

Abstract

Fourier transform microwave (FTMW) spectroscopy has been used for many years as one of the most accurate methods to determine gas-phase structures of molecules and small molecular clusters. In the last years two pioneering works ushered in a new era applications. First, by exploiting the reduced measurement time and the high sensitivity, the development of chirped-pulse CP-FTMW spectrometers\footnote{G. G. Brown, B. C. Dian, K. O. Douglass, S. M. Geyer, S. T. Shipman, B. H. Pate, Rev. Sci. Instrum. 2008, 79, 053103.} enabled the full structural determination of molecules of increasing size as well as molecular clusters. Second, and more recently, Patterson et al.\footnote{D. Patterson, M. Schnell, J. M. Doyle, Nature 2013, 497, 475–477.} showed that rotational spectroscopy can also be used for enantiomer-specific detection. Here we present an experimental approach that combines both in a single spectrometer. This set-up is capable to rapidly obtain the full heavy-atom substitution structure using the CP-FTMW features. The inclusion of an extra set of broadband horns allows for a chirality-sensitive measurement of the sample.\footnote{D. Patterson, J. M. Doyle, Phys. Rev. Lett. 2013, 111, 023008.}$^{,}$\footnote{V. A. Shubert, D. Schmitz, D. Patterson, J. M. Doyle, M. Schnell, Angew. Chem. Int. Ed. 2014, 53, 1152–1155.} The measurement we implement is a three-wave mixing experiment that uses time-separated pulses to optimally create the chiral coherence – an approach that was proposed recently.\footnote{J.-U. Grabow, Angew. Chem. 2013, 125, 11914 – 11916; Angew. Chem. Int. Ed. 2013, 52, 11698 –11700.} Using samples of R-, S- and racemic Solketal, the physical properties of the three-wave mixing experiment were studied. This involved the measurement of the corresponding nutation curves (molecular signal intensity vs excitation pulse duration) to demonstrate the optimal pulse sequence. The phase stability of the chiral signal, required to assign the absolute stereochemistry, has been studied as a function of the measurement signal-to-noise ratio using a “phasogram” method.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/51188

DOI

https://doi.org/10.15278/isms.2014.TB02

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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