| Budget Amount *help |
¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2002: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 2001: ¥900,000 (Direct Cost: ¥900,000)
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| Research Abstract |
1. To elucidate the nature of a pseudo-Jahn-Teller (JT) distortion from planarity, we carried out ab initio MCSCF calculations with 6-31G(d, p) basis sets in the ground states of seven- and eight-membered unsaturated heterocucles with eight π electrons. For instances, azepine and oxepin undergo the pseudo-JT distortions from a planar C_<2v> to a boat C_s conformation. In 1,5-diazocine, the pseudo-JT distortion takes place in two stages, the initial step being from a symmetric planar D_<2h> to a skew C_<2h> structure and the subsequent step from the skew C_<2h> to a tub C_2 structure.
2. We also studied the nature of the pseudo-JT distortion from planarity in the ground states of [n] circulenes by means of the ab initio MCSCF method with 6-31G(d) basis sets. For instances, it was found that [4] circulene undergoes the pseudo-JT distortion from a planar D_<4h> to a deep bowl-shaped C_<4v> structure. Also in [5] circulene, a very similar pseudo-JT distortion occurs from a planar D_<5h> to a shallow bowl-shaped C_<5v> structure.
3. Energy component analysis of the total energy reveals that the present pseudo-JT effects lead commonly to a lowering of the electron-nuclear attraction energy and, concomitantly, to a raising of both the interelectronic and internuclear repulsion energies. In conclusion, these energy variations are accounted for in terms of an electrostatic interaction and the proximity among the nuclei and electron clouds owing to a folding of the molecular skeleton.
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