Schroeder Zachary W, Rezghi Rami Parisa, Adam Matthias, Ferguson Michael J, Hampel Frank, Tykwinski Rik R
Department of Chemistry, University of Alberta, Edmonton, Alberta, T6G 2G2, Canada.
Department of Chemistry and Pharmacy & Interdisciplinary Center for Molecular Materials (ICMM), University of Erlangen-Nuremberg, Nikolaus-Fiebiger Str. 10, 91058, Erlangen, Germany.
Chemistry. 2024 Dec 10;30(69):e202402651. doi: 10.1002/chem.202402651. Epub 2024 Oct 25.
6,13-Diethynylpentacene derivatives with sterically bulky substituents (Tr*, tris(3,5-di-tert-butylphenyl)methyl groups) appended to the ethynyl moieties at the 6- and 13-positions have been synthesized, as well as derivatives with electron-withdrawing fluorine groups on the 1,2,3,4,8,9,10,11-positions. These molecules are designed to investigate relationships between steric and electronic effects on the stability of pentacene toward endoperoxide formation via reaction with photosensitized oxygen in solution under ambient light (i. e., 'laboratory' conditions). It is evident from the study that stabilization through changes to the electronic characteristics of pentacene are more effective than the incorporation of sterically bulky groups at the acetylenic termini. Selected pentacene derivatives have been made into binary, amorphous films with the fullerene derivative PCBM to investigate the stability imparted by substituents against cycloaddition reactions. Overall, the introduction of steric protection through the incorporation of Tr* groups is not an efficient strategy for enhancing the persistence of pentacenes. Stabilization through fluorination proves successful for extending the lifetime of the pentacene derivatives by an order of magnitude in solution. Notably, the persistence of pentacene derivatives in solution can also be enhanced through the use of ethereal solvents stabilized with butylated hydroxy toluene (BHT) and/or an increased number of trialkylsilyl groups as substituents.
已合成了在6和13位乙炔基部分带有空间位阻大的取代基（Tr*，三（3,5-二叔丁基苯基）甲基）的6,13-二乙炔基并五苯衍生物，以及在1,2,3,4,8,9,10,11位带有吸电子氟基团的衍生物。这些分子旨在研究在环境光（即“实验室”条件）下，空间效应和电子效应与并五苯在溶液中与光敏氧反应形成内过氧化物稳定性之间的关系。研究表明，通过改变并五苯的电子特性实现的稳定化比在炔基末端引入空间位阻大的基团更有效。已将选定的并五苯衍生物与富勒烯衍生物PCBM制成二元非晶薄膜，以研究取代基对环加成反应的稳定性。总体而言，通过引入Tr*基团进行空间保护不是提高并五苯持久性的有效策略。通过氟化实现的稳定化成功地将并五苯衍生物在溶液中的寿命延长了一个数量级。值得注意的是，通过使用用丁基化羟基甲苯（BHT）稳定的醚类溶剂和/或增加作为取代基的三烷基硅基的数量，也可以提高并五苯衍生物在溶液中的持久性。
