Low‐Barrier Hydrogen Bonds in Negative Thermal Expansion Material H3[Co(CN)6]

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The covalent nature of the low-barrier N−H−N hydrogen bonds in the negative thermal expansion material H 3[Co(CN) 6] has been established by using a combination of X-ray and neutron diffraction electron density analysis and theoretical calculations. This finding explains why negative thermal expansion can occur in a material not commonly considered to be built from rigid linkers. The pertinent hydrogen atom is located symmetrically between two nitrogen atoms in a double-well potential with hydrogen above the barrier for proton transfer, thus forming a low-barrier hydrogen bond. Hydrogen is covalently bonded to the two nitrogen atoms, which is the first experimentally confirmed covalent hydrogen bond in a network structure. Source function calculations established that the present N−H−N hydrogen bond follows the trends observed for negatively charge-assisted hydrogen bonds and low-barrier hydrogen bonds previously established for O−H−O hydrogen bonds. The bonding between the cobalt and cyanide ligands was found to be a typical donor–acceptor bond involving a high-field ligand and a transition metal in a low-spin configuration.

Original languageEnglish
JournalChemistry: A European Journal
Pages (from-to)6814-6822
Number of pages9
Publication statusPublished - May 2019

    Research areas

  • X-ray diffraction, chemical bonding, electron density, hydrogen bonds, neutron diffraction, NEUTRON, OUTLIER, X-RAY-DIFFRACTION, CHARGE-DENSITY, WAVE-FUNCTIONS, CATALYTIC TRIAD, MODEL-COMPOUND, ATOMS, SCATTERING

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