" A Quantum Chemical Investigation of the C-O Bond Length and Stretching Mode of the Phenolate Anion"M. Nonella, H.U. Sutter
J. Phys. Chem. 102A, 1998, 10128-10133.
Structure and vibrational spectrum of the phenolate anion have been
calculated with various quantum chemical methods. Correlated methods
predict a C-O bond length between 1.28 and 1.29 Å which is
significantly shorter than an earlier suggested value of 1.40 Å.
This indicates a partial double bond character for the C-O bond in the
phenolate anion which is explained in terms of resonance structures. IR
frequencies determined with pure density functional methods agree well
with FTIR data in the case of the modes n4
and n5 while the frequency of the
C-O mode is significantly overestimated in all calculations. The
calculations of the isolated phenolate anion do thus poorly agree with
experimental data. We demonstrate, that upon complexation of the phenolate
anion with a positively charged counter ion the C-O bond is elongated and
becomes considerable single bond character. The intermolecular interaction
also causes a down shift of 30 cm-1 of the C-O stretching mode
and thus reveals a better agreement with experimental data.
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