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Researchers probe hydrogen bonds with new technology

Hydrogen bond strength to iron (III) oxido / hydroxido (FeIII-O / OH) units in non-iron iron complexes is revealed by…

Hydrogen bond strength to iron (III) oxido / hydroxido (FeIII-O / OH) units in non-iron iron complexes is revealed by FeIII-O / OH stretching vibration detected with 57Fe nuclear resonance vibration spectroscopy (NRVS). Credit: Carnegie Mellon University

Researchers at Carnegie Mellon University have used nuclear resonance vibration spectroscopy to investigate hydrogen bonds that modulate the chemical reactivity of enzymes, catalysts and biomimetic complexes. The technology can lead to the development of better catalysts for use in a wide range of areas. The findings were published as a “very important paper” in the December 3 issue of Angewandte Chemie and featured on the journal back cover.

Hydrogen bonds are among the most fundamental interactions in biology and chemistry. They are responsible for many of the chemically important properties of water, to stabilize the structures of proteins and nucleic acids, including those found in DNA and RNA, and contribute to the structure of natural and synthetic polymers.

Research has shown that hydrogen bonds play an important role in setting the reactivity of the metal centers of metallo-enzymes and metal-containing catalysts. However, little research has been done to experimentally demonstrate how systematic changes of hydrogen bonds within the secondary coordination sphere molecules are located near metal centers that do not have direct-link interactions with the central impact catalytic activity.

In catalytic enzymes or synthetic catalysts, a chemical reaction chain is used which produces a number of intermediate structures or species. Understanding these structures and their chemical properties is the key to understanding the whole reaction.

“Understanding the chemical reactivity of the reactive intermediate is an important step in determining how to design highly efficient and selective catalysts for CH functionalization,” said Yisong Guo, professor of chemistry at Carnegie Mellon, and the lead author of the study. “In dioxygen activating enzymes, the major intermediate catalysts are iron oxo (Fe-O) and iron hydroxo (Fe-OH) species which are involved in important biological processes, such as DNA biosynthesis, DNA and RNA repair, post-translational protein modification , biosynthesis of antibiotics and digestion of toxic compounds. “

Guo and colleagues used 57Fe nuclear resonance vibration spectroscopy, a newly developed synchrotron radiation-based technique for detecting the vibration frequency of Fe-O and Fe-OH units of synthetic complexes that interact with the secondary coordination sphere through hydrogen bonds. Changes in frequencies revealed valuable information on the binding strength of these devices and further provided a qualitative measurement of hydrogen bonding strength.

“This showed that NRVS is a sensitive technique for collecting very small changes in hydrogen bonding strength down to the changes of a single hydrogen bond. This gives us a new method of joining changes in bond strength of Fe-O and Fe-OH- Guo says that this study is a proof -of the concept of using NRVS to probe hydrogen bonds. He plans to continue using this method to study more iron oxide and iron hydroxides in both synthetic complexes and enzymes to build up the amount of available data to correlate chemical reactivity of these species with the changes of hydrogen bonding interactions, hoping that that information could be used to develop more efficient and effective catalysts.

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More information:
Andrew C. Weitz et al., Probing Hydrogen Bonding Interactions to Iron Oxido / Hydroxido Units by 57 Fe Nuclear Resonance Vibrational Spectroscopy, Angewandte Chemie International Edition (2018). DOI: 10.1002 / anie.201810227

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