Direct Experimental Observation of the Tetrabromine Cluster Br4 by Synchrotron Photoionization Mass Spectrometry

Rory McClish; Giovanni Meloni

doi:10.1002/open.202300266

Direct Experimental Observation of the Tetrabromine Cluster Br₄ by Synchrotron Photoionization Mass Spectrometry

ChemistryOpen. 2024 Feb 2:e202300266. doi: 10.1002/open.202300266. Online ahead of print.

Authors

Rory McClish¹, Giovanni Meloni^{1

2}

Affiliations

¹ Department of Chemistry, University of San Francisco, San Francisco, CA 94117, USA.
² Department of Biological and Chemical Sciences, New York Institute of Technology, Old Westbury, NY 11568, USA.

PMID: 38308191
DOI: 10.1002/open.202300266

Abstract

We present a first spectroscopic characterization of the homoatomic polyhalogen tetrabromine, Br₄ , in the gas phase. Photolysis of CHBr₃ at 248 nm is used to generate atomic bromine radicals in a flow tube reactor. Resulting combination products are detected by photoionization mass spectrometry at the Advanced Light Source of the Lawrence Berkeley National Laboratory. Interpretation of the experimental mass spectra is informed by calculated adiabatic ionization energies carried out at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ//cam-B3LYP/6-311++g** levels of theory. Tunable VUV synchrotron radiation enables the collection of the mass-selected photoionization spectra by which Br₄ is assigned using Franck-Condon simulations of a Br₂ dimer with a stretched tetrahedral geometry.

Keywords: adiabatic ionization energy; distorted tetrahedral D2h structure; multiplexed mass spectrometry; synchrotron photoionization; tetrabromine cluster.