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"Structures and harmonic force fields of 1,4-naphthoquinone and
naphthalene: a density functional study." M. NonellaJ. Molec. Struct. (THEOCHEM) 362, 7-21, (1996) Abstract: Structures and harmonic force fields of 1,4-naphthoquinone and naphthalene have been calculated using density functional methods. In contrast to X-ray investigations and in agreement with semi empirical and ab initio Hartree-Fock calculations, our study reveals that 1,4-naphthoquinone can be considered in good approximation as a system of weakly interacting p-benzoquinone and benzene molecules where only the bond connecting the two moieties is considerably perturbed. This bond is increased by about 0.015 Å compared to the bond length of benzene. Vibrational frequencies calculated with the quantum chemically derived unscaled harmonic force field are generally in good agreement with experimental data. In contradiction to previous semi empirical and ab initio Hartree-Fock calculations, a similar but smaller enlargement of the connecting bond is also found in naphthalene. Previous calculations of vibrational frequencies based on theoretical, scaled Hartree-Fock force fields have shown that the length of this connecting bond is one of the crucial parameters which determines the agreement theoretical frequencies with experimental data. BMO authors (in alphabetic order): Marco Nonella |