Unprecedented light induced aggregation of cationic 1,4,5,8-Naphthalenediimide amphiphiles [dataset]

Bola amphiphiles from naphthalenediimide (NDI-bas) with quaternary ammonium groups (DC4, DaP, and DaO) display association in solution, as well as, surprisingly, visible light promoted photochromism in concentrated solutions of water, acetonitrile and THF. The photochromism is correlated with an aggregation process that leads to a significant modification of the electronic transitions, resulting in an unusual absorption band distribution that points out to a type of H-aggregation in transverse. This assembly can be reversibly broken up by heating at 70 °C and adding bulk salt (NaBF4). By 1H-NMR spectroscopic analysis of the irradiation/heating cycle the assembly/disassembly process can be followed by the changes in peak width and intensity. These photoinduced aggregates can sensitize dissolved O2 to give singlet oxygen, a surprising observation when it comes to sensitization efficiency for dyes where aggregation usually decreases the sensitization yield. Laser-induced luminescence measurements corroborate the existence of triplet states as phosphorescence was detected, being particularly intense in concentrated THF solutions.

基于萘二酰亚胺（naphthalenediimide，NDI-bas）的bola两亲分子（Bola amphiphiles）带有季铵基团，其代表性分子包括DC4、DaP与DaO，这类分子在溶液中表现出缔合行为，且在水、乙腈与四氢呋喃（THF）的浓溶液中展现出出人意料的可见光诱导光致变色现象。该光致变色过程与聚集过程紧密相关，聚集会引发电子跃迁的显著改变，进而形成异常的吸收带分布，表明体系中存在横向H聚集体。该组装体可通过70℃加热以及加入大量四氟硼酸钠（NaBF4）实现可逆解离。通过对辐照-加热循环进行核磁共振氢谱（1H-NMR）分析，可通过峰宽与峰强的变化追踪组装与解离过程。这类光诱导聚集体能够敏化溶解氧以产生单线态氧——在通常认为聚集会降低染料敏化产率的体系中，这一敏化效率表现颇为出人意料。激光诱导发光测试证实了三重态的存在，且检测到了磷光信号，该信号在浓四氢呋喃溶液中尤为强烈。