title: Proton Probability Distribution in the O···H···O Low-Barrier Hydrogen Bond: A Combined Solid-State NMR and Quantum Chemical Computational Study of Dibenzoylmethane and Curcumin.
abstract: We report a combined solid-state (1H,2H,13C,17O) NMR and plane-wave density functional theory (DFT) computational study of the O···H···O low-barrier hydrogen bonds (LBHBs) in two 1,3-diketone compounds: dibenzoylmethane (1) and curcumin (2). In the solid state, both 1 and 2 exist in the cis-keto-enol tautomeric form, each exhibiting an intramolecular LBHB with a short O···O distance (2.435 Å in 1 and 2.455 Å in 2). Whereas numerous experimental (structural and spectroscopic) and computational studies have been reported for the enol isomers of 1,3-diketones, a unified picture about the proton location within an LBHB is still lacking. This work reports for the first time the solid-state17O NMR data for the O···H···O LBHBs in 1,3-diketones. The central conclusion of this work is that detailed information about the probability density distribution of the proton (nuclear zero-point motion) across an LBHB can be obtained from a combination of solid-state NMR and plane-wave DFT computations (both NMR parameter calculations and ab initio molecular dynamics simulations). We propose that the precise proton probability distribution across an LBHB should provide a common basis on which different and sometimes seemingly contradicting experimental results obtained from complementary techniques, such as X-ray diffraction, neutron diffraction, and solid-state NMR, can be reconciled.
authors: Department of Chemistry, Queen's University , 90 Bader Lane, Kingston, Ontario, Canada K7L 3N6.
authors: Xianqi
authors: X
authors: Kong
authors: Measurement Science and Standards, National Research Council Canada , 1200 Montreal Road, M-40, Ottawa, Ontario, Canada K1A 0R6.
authors: Andreas
authors: A
authors: Brinkmann
authors: Department of Chemistry, Queen's University , 90 Bader Lane, Kingston, Ontario, Canada K7L 3N6.|Department of Chemistry, University of Ottawa , 10 Marie Curie Private, Ottawa, Ontario, Canada K1N 6N5.
authors: Victor
authors: V
authors: Terskikh
authors: Department of Chemistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G2.
authors: Roderick E
authors: RE
authors: Wasylishen
authors: Department of Chemistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G2.
authors: Guy M
authors: GM
authors: Bernard
authors: Department of Chemistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G2.
authors: Zhuang
authors: Z
authors: Duan
authors: Department of Chemistry, University of Alberta , Edmonton, Alberta, Canada T6G 2G2.
authors: Qichao
authors: Q
authors: Wu
authors: Department of Chemistry, Queen's University , 90 Bader Lane, Kingston, Ontario, Canada K7L 3N6.
authors: Gang
authors: G
authors: Wu