Department of Molecular and Macromolecular Chemistry, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan.
Spectroscopy Laboratory for Functional π-Electronic Systems and Department of Chemistry, Yonsei University, Seoul, 03722, South Korea.
Chemistry. 2020 Feb 26;26(12):2754-2760. doi: 10.1002/chem.201905402. Epub 2020 Feb 6.
N-Alkylation significantly changes the electronic and optical properties, as well as the reactivity of nitrogen-containing π-conjugated molecules. In this study, it is found that treating 5,15-diazaporphyrins with methyl triflate selectively affords the corresponding N-methyl-5,15-diazaporphyrinium cations in good yield. N-Methylation substantially alters the electronic properties and reactivity of diazaporphyrins. The electron-accepting properties of the N-methyl-5,15-diazaporphyrinium cations are enhanced due to their lowered LUMO level. Stabilization of the LUMO energy enables regio- and stereoselective Diels-Alder reactions of the cationic diazaporphyrin with cyclopentadiene. N-Methylation also enhances the acidity of the inner NH protons, and thus, allows facile deprotonation to provide nitrogen-substituted isoporphyrin analogues with only one NH group in the central cavity.
N-烷基化显著改变了含氮π共轭分子的电子和光学性质以及反应活性。在这项研究中，发现用甲基三氟甲磺酸处理 5,15-二氮杂卟啉可以以良好的产率选择性地得到相应的 N-甲基-5,15-二氮杂卟啉𬭩阳离子。N-甲基化会显著改变二氮杂卟啉的电子性质和反应活性。由于其较低的 LUMO 能级，N-甲基-5,15-二氮杂卟啉𬭩阳离子的电子接受性质得到增强。LUMO 能量的稳定化使得阳离子二氮杂卟啉与环戊二烯发生区域和立体选择性的 Diels-Alder 反应成为可能。N-甲基化还增强了内 NH 质子的酸性，从而使质子化容易发生，仅在中心腔中提供一个 NH 基团的氮取代异卟啉类似物。
