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Internet Electronic Journal of Molecular Design - IEJMD, ISSN 1538-6414, CODEN IEJMAT
| ABSTRACT - Internet Electron. J. Mol. Des. June 2002, Volume 1, Number 6, 285-292 |
A Hellmann-Feynman Basis for the Determination of the Dependence of
the Intramolecular X-H(D) Potential on the Hydrogen Bond Strength
Ljupco Pejov
Internet Electron. J. Mol. Des. 2002, 1, 285-292
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Abstract:
A novel theoretical method that enables extraction of the function
describing the dependence of the decoupled X-H(D) intramolecular
potential on the hydrogen bond strength from experimental
frequency-structure correlation equations is proposed. The method is based on the
Hellmann-Feynman theorem, using the perturbed anharmonic
oscillator wavefunctions, and the conceptual approach of Sceats and
Rice. Within the proposed method, other parameters obtained by
empirical correlations have also exact physical meanings. The
hydrogen bonding is beyond doubt one of the most interesting
interactions from both fundamental and application viewpoints. A lot
of experimental data have been collected so far regarding the
spectroscopic manifestations of this interaction, among which the most
important is the frequency downshift of the X-H stretching mode. A
number of empirical correlations have been performed for the
dependence of ν01,XH(D) versus RX...Y
in hydrogen bonded X-H...Y
systems. However, there is still a lack of systematic theoretical basis
for the empirical correlation functions which are widely applicable.
Also, it would be especially interesting to extract the function
describing the dependence of the intramolecular X-H(D) potential on
the hydrogen bond strength obtained from experimental
frequency-structure correlations. The Hellmann-Feynman theorem, in
combination with the stationary perturbation theory in the
non-degenerate case for the representation of anharmonic oscillator
perturbed (by hydrogen bonding) wavefunction, is applied. It is shown
that there is a solid theoretical basis for the empirical spectra-structure
correlations in the case of hydrogen bonded systems. Moreover, on the
basis of the derived theoretical model, "extraction" of the function
describing the dependence of the intramolecular X-H(D) potential on
the hydrogen bond strength becomes possible using experimental
frequency-structure correlation data. Within the conceptual approach
of Sceats and Rice, a Hellmann-Feynman based theoretical model is
derived, that enables determination of the function describing the
dependence of the intramolecular X-H(D) potential on the hydrogen
bond strength, derived from experimental frequency-structure
correlations. Within the proposed method, other empirically obtained
parameters have exact physical meanings as well. The proposed
approach may serve to test the validity and physical basis of various
model functions used for empirical correlations.
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