Effect of the Meso-Substituent in the H眉ckel-to-M枚bius Topological Switches

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• 作者：Enrique Marcos ; Josep M. Anglada ; Miquel Torrent-Sucarrat
• 刊名：Journal of Organic Chemistry
• 出版年：2014
• 出版时间：June 6, 2014
• 年：2014
• 卷：79
• 期：11
• 页码：5036-5046
• 全文大小：432K
• 年卷期：v.79,no.11(June 6, 2014)
• ISSN：1520-6904

文摘

Expanded porphyrins have emerged as a new promising class of molecules for the creation of new H眉ckel-to-M枚bius topological switches with distinct aromaticities and magnetic and electric properties. In this work, we report a theoretical investigation of the conformational switch between the H眉ckel planar and the singly twisted M枚bius structure for eight different meso-substituted [28]-hexaphyrins (with different steric effects and electron-withdrawing and -releasing character). Our results show how a change in the nature of the meso-substituent is able to turn an endothermic interconversion process with a high energy barrier into an exothermic and almost barrierless H眉ckel鈥揗枚bius transition. We also provide a thorough analysis of the main factors (aromaticity, intramolecular hydrogen bonds, ring strain, and steric effects) that play a role in this interconversion process. Overall, these results are very relevant to find new ways to control the thermochemistry and kinetics of these topological switches and even 鈥渇reeze鈥?the switch in the desired M枚bius or H眉ckel conformation.