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"Formation of phenolate anion-counter ion complexes can explain the vibrational properties of the phenolate anion in solution" M. Nonella, H.U. SutterJ. Phys. Chem. 103A, 1999, 7867-7871. Abstract: Structures of enolate-counter ion complexes and structures and vibrational spectra of phenolate anion-counter ion complexes have been calculated by means of MP2 and density functional methods. Compared to corresponding monomeric complexes, higher complexes reveal longer C-O bond lengths which causes a downshift of the C-O stretching mode. In the case of phenolate we find C-O stretching frequencies and isotope shifts upon 18O and d2 labeling which are in good agreement with recent IR data of phenolate generated in solution. The C-O stretching frequency, for example, is predicted to be around 1270 cm-1 compared to an experimental value of 1273 cm-1 and the 18O shift of this mode is calculated to be 18 cm-1 compared to an experimental shift of 17 cm-1. For a free phenolate anion, our calculations predict a C-O stretching frequency of 1350 cm-1. The vibrational spectrum of phenolate anions in solution can thus be explained in terms of higher phenolate anion-counter ion complexes in agreement with recent NMR experiments of Jackman and Smith (J. Am. Chem. Soc. 1988, 110, 3829). BMO authors (in alphabetic order): Marco Nonella |