Arene Substitution Design for Controlled Conformational Changes of Dibenzocycloocta-1,5-dienes

Wenxin Fu, Todd M. Alam, Jiachen Li, Jacqueline Bustamante, Thanh Lien, Ralph W. Adams, Simon J. Teat, Benjamin J. Stokes, Weitao Yang, Yi Liu, Jennifer Q. Lu

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Abstract

We report that the agile eight-membered cycloalkane can be stabilized by fusing two rigid benzene rings, substituted with proper functional groups. The conformational change of dibenzocycloocta-1,5-diene (DBCOD), a rigid-flexible-rigid organic moiety, from Boat to Chair conformation requires an activation energy of 42 kJ/mol that is substantially lower than that of existing submolecular shape-changing unit. Experimental data corroborated by theory calculations demonstrate that intramo-lecular hydrogen bonding can stabilize Boat whereas electron repulsive interaction from opposing ester substituents favors Chair. Intramolecular hydrogen bonding, formed by 1,10-diamide substitution stabilizes Boat, spiking the temperature at which Boat and Chair can readily interchange from –60 °C to 60 °C. Concomitantly this intramolecular attraction raises the energy barrier from 42 kJ/mol of unsubstituted DBCOD to 68 kJ/mol of diamide-substituted DBCOD. Remarkably, this value falls within the range of the activation energy of highly efficient enzyme catalyzed biological reactions. With shape changes once considered only possible with high-energy, our work reveals a potential pathway exemplified by a specific submolecu-lar structure to achieve low-energy driven shape changes for the first time. Together with intrinsic cycle stability and high energy output systems that would have incurred damage under high-energy stimuli, could particularly benefit from this new kind of low-energy driven shape-changing mechanism. This work has laid the basis to construct systems for low-energy driv-en stimuli-responsive applications, hitherto a challenge to overcome.
Original languageEnglish
JournalJournal of the American Chemical Society
Early online date3 Sept 2020
DOIs
Publication statusE-pub ahead of print - 3 Sept 2020

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