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Why bistetracenes are much less reactive than pentacenes in Diels-Alder reactions with fullerenes

The Diels-Alder (DA) reactions of pentacene (PT), 6,13-bis(2-trimethylsilylethynyl)pentacene (TMS-PT), bistetracene (BT), and 8,17-bis(2-trimethylsilylethynyl)bistetracene (TMS-BT) with the [6,6] double bond of [60]fullerene have been investigated by density functional theory calculations. Reaction barriers and free energies have been obtained to assess the effects of frameworks and substituent groups on the DA reactivity and product stability. Calculations indicate that TMS-BT is about 5 orders of magnitude less reactive than TMS-PT in the reactions with [60]fullerene. This accounts for the observed much higher stability of TIPS-BT than TIPS-PT when mixed with PCBM. Surprisingly, calculations predict that the bulky silylethynyl substituents of TMS-PT and TMS-BT have only a small influence on reaction barriers. However, the silylethynyl substituents significantly destabilize the corresponding products due to steric repulsions in the adducts. This is confirmed by experimental results here. Architectures of the polycyclic aromatic hydrocarbons (PAHs) play a crucial role in determining both the DA barrier and the adduct stability. The reactivities of different sites in various PAHs are related to the loss of aromaticity, which can be predicted using the simple Hückel molecular orbital localization energy calculations

American Chemical Society (ACS)

Author: Cao, Yang
Liang, Yong
Zhang, Lei
Houk, Kendall N.
Osuna Oliveras, Sílvia
Hoyt, Andra Lisa M.
Briseño, Alejandro L.
Date: 2014
Abstract: The Diels-Alder (DA) reactions of pentacene (PT), 6,13-bis(2-trimethylsilylethynyl)pentacene (TMS-PT), bistetracene (BT), and 8,17-bis(2-trimethylsilylethynyl)bistetracene (TMS-BT) with the [6,6] double bond of [60]fullerene have been investigated by density functional theory calculations. Reaction barriers and free energies have been obtained to assess the effects of frameworks and substituent groups on the DA reactivity and product stability. Calculations indicate that TMS-BT is about 5 orders of magnitude less reactive than TMS-PT in the reactions with [60]fullerene. This accounts for the observed much higher stability of TIPS-BT than TIPS-PT when mixed with PCBM. Surprisingly, calculations predict that the bulky silylethynyl substituents of TMS-PT and TMS-BT have only a small influence on reaction barriers. However, the silylethynyl substituents significantly destabilize the corresponding products due to steric repulsions in the adducts. This is confirmed by experimental results here. Architectures of the polycyclic aromatic hydrocarbons (PAHs) play a crucial role in determining both the DA barrier and the adduct stability. The reactivities of different sites in various PAHs are related to the loss of aromaticity, which can be predicted using the simple Hückel molecular orbital localization energy calculations
Format: application/pdf
Document access: http://hdl.handle.net/10256/10362
Language: eng
Publisher: American Chemical Society (ACS)
Collection: info:eu-repo/semantics/altIdentifier/doi/10.1021/ja505240e
info:eu-repo/semantics/altIdentifier/issn/0002-7863
info:eu-repo/semantics/altIdentifier/eissn/1520-5126
info:eu-repo/grantAgreement/EC/FP7/630978/EU/Computational Exploration of Directed Evolution rules for tuning enzymatic activities/DIREVENZYME
info:eu-repo/grantAgreement/EC/FP7/252856/EU/Enzyme Design of Medical Interest/MEDENZYMEDESIGN
Rights: Tots els drets reservats
Subject: Diels-Alder, Reacció de
Diels-Alder reaction
Fullerenes
Ful·lerens
Title: Why bistetracenes are much less reactive than pentacenes in Diels-Alder reactions with fullerenes
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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