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Ring Rotation in Biphenyl by William Abbott

Ring Rotation in Biphenyl by William Abbott. Ground State Geometry. While -electron delocalization effects would favor a planar conformation, the steric repulsion between the ortho-hydrogens would favor a staggered position.

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Ring Rotation in Biphenyl by William Abbott

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  1. Ring Rotation in Biphenylby William Abbott

  2. Ground State Geometry While -electron delocalization effects would favor a planar conformation, the steric repulsion between the ortho-hydrogens would favor a staggered position. Torn between these two competing forces, one would expect the equilibrium twist angle to lie somewhere between 0° and 90°.

  3. Various methods were used to calculate ground state energies.Only HF/6-31G* produced a conformational energy minimum which closely corresponds with the gas-phase electron diffraction results of ~44.4° 1,2

  4. Excited State EnergyCalculations were performed for the first excited singlet state. The results indicate a near-planar conformational energy minimum, which accords with indirect Raman spectroscopy evidence3 and with the vibrational structure of the fluorescence spectrum of biphenyl in solution4.

  5. Possible scheme for Fluorescence in Biphenyl

  6. Ground State HOMO

  7. References • Almenningen, A.; Bastiansen, O.; Fernholt, L.; Cyvin, B. N.; Cyvin, S.J.; Samdal, S. J. Mol. Struct.1985, 128, 59. • Bastiansen, O.; Samdal, S. J. Mol. Struct.1985, 128, 115. • Matsunuma, S.; Yamaguchi, S.; Hirosem C.; Maeda, S. J. Phys. Chem.1988, 92, 1777. • Lim, E.C.; Li, Y.H. J. Chem. Phys. 1970, 52, 6416

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