Volume 58, Issue 33 pp. 11400-11403
Communication

Spectroscopic Measurement of a Halogen Bond Energy

Prof. Dr. Xinxing Zhang

Corresponding Author

Prof. Dr. Xinxing Zhang

Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (ReCAST), College of Chemistry, Nankai University, Tianjin, 300071 China

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Dr. Gaoxiang Liu

Dr. Gaoxiang Liu

Departments of Chemistry, Johns Hopkins University, Baltimore, MD, 21218 USA

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Sandra Ciborowski

Sandra Ciborowski

Departments of Chemistry, Johns Hopkins University, Baltimore, MD, 21218 USA

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Wei Wang

Wei Wang

Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (ReCAST), College of Chemistry, Nankai University, Tianjin, 300071 China

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Chu Gong

Chu Gong

Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (ReCAST), College of Chemistry, Nankai University, Tianjin, 300071 China

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Yifan Yao

Yifan Yao

Key Laboratory of Advanced Energy Materials Chemistry (Ministry of Education), Renewable Energy Conversion and Storage Center (ReCAST), College of Chemistry, Nankai University, Tianjin, 300071 China

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Prof. Dr. Kit Bowen

Corresponding Author

Prof. Dr. Kit Bowen

Departments of Chemistry, Johns Hopkins University, Baltimore, MD, 21218 USA

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First published: 11 June 2019
Citations: 17

Dedicated to the 100th anniversary of Nankai University

Graphical Abstract

Strong noncovalent interaction: While halogen bonding has been widely recognized in many fields of chemistry, a benchmark spectroscopic measurement of its strength is still absent. Here, the strength of a poster child halogen bond between Br and CCl3Br using anion photoelectron spectroscopy is reported.

Abstract

Halogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br anions is reported. The XB strength between the positively-charged σ-hole on the Br atom of the bromotrichloromethane (CCl3Br) molecule and the Br anion was found to be 0.63 eV (14.5 kcal mol−1). In the neutral complexes, Br(CCl3Br)1,2, the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl3Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol−1) and 0.12 eV (2.8 kcal mol−1).

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