Kato Takashi, Yamabe Tokio
Fukui Institute for Fundamental Chemistry, Kyoto University, 34-4 Takano-Nishihiraki-cho, Sakyo-ku, 606-8103, Japan.
J Chem Phys. 2004 Aug 1;121(5):2356-66. doi: 10.1063/1.1766018.
The single charge transfer through acenes, partially H-F substituted acenes, and fluoroacenes is discussed. The reorganization energies between the neutral molecules and the corresponding monoanions for partially H-F substituted acenes lie between those for acenes and fluoroacenes. The delocalization of the lowest unoccupied molecular orbitals (LUMO) by substituting hydrogen atoms by fluorine atoms with the highest electronegativity in every element is the main reason why the reorganization energy between the neutral molecule and the monoanion for partially H-F substituted acenes lies between those for acenes and fluoroacenes. This result implies that the negatively charged partially H-F substituted acenes would be better conductors with rapid electron transfer than the negatively charged fluoroacenes if we assume that the overlap of the LUMO between partially H-F substituted acenes is not significantly different from that between two neighboring fluoroacenes. The structures of the monoanions of acenes, fluoroacenes, and partially H-F substituted acenes are optimized under D2h geometry, and the Jahn-Teller effects in the monoanions of benzene and fluorobenzene are discussed. The vibration effect onto the charge transfer problem is also discussed. The C-C stretching modes around 1500 cm(-1) are the main modes converting the neutral molecules to the monoanions in acenes, fluoroacenes, and partially H-F substituted acenes. It can be confirmed from the calculational results that the C-C stretching modes around 1500 cm(-1) the most strongly couple to the LUMO in these molecules. The main reason why the total electron-phonon coupling constants (lLUMO) for the monoanions of acenes in which four outer hydrogen atoms are substituted by fluorine atoms are larger than those for the monoanions of acenes in which several inner hydrogen atoms are substituted by fluorine atoms is suggested. The relationships between the electron transfer and the electron-phonon interactions are discussed. The plot of the reorganization energies against the lLUMO values is found to be nearly linear. In view of these results, the relationships between the normal and superconducting states are briefly discussed.
本文讨论了通过并苯、部分氢氟取代并苯和氟代并苯的单电荷转移。部分氢氟取代并苯的中性分子与相应单阴离子之间的重组能介于并苯和氟代并苯之间。在每个元素中用具有最高电负性的氟原子取代氢原子，使得最低未占据分子轨道（LUMO）发生离域，这是部分氢氟取代并苯的中性分子与单阴离子之间的重组能介于并苯和氟代并苯之间的主要原因。该结果表明，如果假设部分氢氟取代并苯之间的LUMO重叠与两个相邻氟代并苯之间的重叠没有显著差异，那么带负电荷的部分氢氟取代并苯将比带负电荷的氟代并苯是更好的导体，具有更快的电子转移。在D2h几何构型下优化了并苯、氟代并苯和部分氢氟取代并苯单阴离子的结构，并讨论了苯和氟苯单阴离子中的 Jahn-Teller 效应。还讨论了振动对电荷转移问题的影响。在并苯、氟代并苯和部分氢氟取代并苯中，1500 cm(-1) 附近的 C-C 伸缩模式是将中性分子转化为单阴离子的主要模式。从计算结果可以证实，1500 cm(-1) 附近的 C-C 伸缩模式与这些分子中的 LUMO 耦合最强。提出了四个外部氢原子被氟原子取代的并苯单阴离子的总电子 - 声子耦合常数（lLUMO）大于几个内部氢原子被氟原子取代的并苯单阴离子的总电子 - 声子耦合常数的主要原因。讨论了电子转移与电子 - 声子相互作用之间的关系。发现重组能与 lLUMO 值的关系图几乎是线性的。鉴于这些结果，简要讨论了正常态与超导态之间的关系。
