IS THERE A HYDROGEN BOND RADIUS?
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Date
2002
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Ohio State University
Abstract
Pauling defined covalent radii, ionic radii and metallic radii for several atoms which were useful in estimating interatomic distances within a $molecule/metal.^{a}$. Similarly van der Waals radius was defined to estimate the inter-molecular distances in crystals. Hydrogen bonding interactions have been known for more than eight decades now. However, accurate geometrical determination of hydrogen bonded complexes could be done in the last 3 decades only, beginning with the classical study on $(HF)_{2}$ by Klemperer and $coworkers.^{b}$ With the advent of pulsed nozzle Fourier transform microwave $spectrometer^{c}$ a wealth of experimental data has now become available. By evaluating ! the available structural data, we defined hydrogen bond radii for the hydrogen halides, such as HF, HCl, HBr and HCN $recently.^{d}$ An empirical correlation between the hydrogen bond radius and the dipole moment of the HX was also found. In this talk, we extend the analysis to $H_{2}O$ and HCCH complexes to define hydrogen bond radius for $OH (0.78 +/- 0.07 {\AA})$ and $CH (1.09+/-0.05 {\AA})$ groups. The value for CH group is very close to the van der Waals radius for H atom as expected from the dipole moment correlation. Is hydrogen bond radius real? A critical evaluation of the data and our analysis will be given during the talk.
Description
$^{a}$L. Pauling, The nature of chemical bond Cornell University Press (1960).$^{b}$T. R. Dyke, B. J. Howard and W. Klemperer J. Chem. Phys. 56, 2442 (1972).$^{c}$T. J. Balle and W. H. Flygare Rev. Sci. Instrumen. 52, 33 (1981). $^{d}$P. K. Mandal and E. Arunan J. Chem. Phys. 114, 3880 (2001).
Author Institution: Department of Inorganic and Physical Chemistry, Indian Institute of Science
Author Institution: Department of Inorganic and Physical Chemistry, Indian Institute of Science