HOMO-LUMO Energy-Gap Tuning of π-Conjugated Zwitterions Composed of Electron-Donating Anion and Electron-Accepting Cation
HOMO-LUMO Energy-Gap Tuning of π-Conjugated Zwitterions Composed of Electron-Donating Anion and Electron-Accepting Cation
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由供电子阴离子和受电子阳离子组成的 π 共轭两性离子的 HOMO-LUMO 能隙调节
DOI：
10.1021/acs.joc.0c02343
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
Yoshida Jun-ichi
中科院分区：
文献类型：
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作者：
Shimizu Akihiro;Ishizaki Yu;Horiuchi Shun;Hirose Takashi;Matsuda Kenji;Sato Hiroyasu;Yoshida Jun-ichi
具有小的最高占据轨道和最低空轨道能隙的π共轭分子(ΔEH-L)因其独特的光电性质而受到广泛的研究。虽然π共轭展开是设计ΔEH-L值较小的分子的著名方法之一，但这种方法不可避免地会产生大的π共轭分子，有时会遇到合成困难和有机溶剂溶解度低的问题。为了开发相对较小的ΔEH-L值的供体-受体分子，我们设计并合成了π共轭的两性离子，这些两性离子由给电子的阴离子如酚氧化物和类氧化物以及接受电子的阳离子如吡啶和吖啶组成。阴离子的HOMO和阳离子的LUMO之间的能量差(ΔED-A)和它们之间的面间夹角(φDA)对ΔEH-L，从而对这些两性离子的电子结构和光电性质有重要的影响。具有小ΔED-A和大φDA的两性离子具有约1 eV的小ΔEH-L值，并表现出两性氧化还原性质和超过λ=1 000 nm的近红外电子吸收。近红外吸收与溶剂的极性、温度和酸的加入有关。这种分子设计将产生小的π共轭的供体-受体分子，具有小的ΔEH-L值。
π-Conjugated molecules with small highest occupied molecular orbital (HOMO)–lowest unoccupied molecular orbital (LUMO) energy gaps (ΔEH–L) have been extensively studied because of their unique optoelectronic properties. Although the expansion of π-conjugation is one of the well-known approaches for designing molecules with small ΔEH–Lvalues, such an approach inevitably gives large π-conjugated molecules sometimes suffering from synthetic difficulty and low solubility toward organic solvents. To develop relatively small donor–acceptor molecules with small ΔEH–Lvalues, we have designed and synthesized π-conjugated zwitterions composed of electron-donating anions, such as phenoxide and anthroxide, and electron-accepting cations, such as pyridinium and acridinium. The energy difference between the HOMO of the anion and the LUMO of the cation (ΔED–A) and the interplanar angle between them (φDA) have a crucial effect on ΔEH–L, and hence, on the electronic structures and optoelectronic properties of these zwitterions. The zwitterions with small ΔED–Aand large φDAhave a small ΔEH–Lof ca. 1 eV and show amphoteric redox properties and near-infrared (NIR) electronic absorption exceeding λ = 1000 nm. The NIR absorption responds to solvent polarity, temperature, and acid addition. This molecular design will generate small π-conjugated donor–acceptor molecules with small ΔEH–Lvalues.