Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University, Mlynská dolina, SK-84215 Bratislava, Slovakia.
J Org Chem. 2010 May 7;75(9):3053-68. doi: 10.1021/jo100359q.
A series of novel heterocycle-based dyes with donor-pi-bridge-acceptor-pi-bridge-donor (D-pi-A-pi-D) structural motif, where benzothiazole serves as an electron-withdrawing core, have been designed and synthesized via palladium-catalyzed Sonogashira and Suzuki-type cross-coupling reactions. All the target chromophores show strong one-photon and two-photon excited emission. The maximum two-photon absorption (TPA) cross sections delta(TPA) of the prepared derivatives bearing diphenylamino functionalities occur at wavelengths ranging from 760 to 800 nm and are as large as approximately 900-1100 GM. One- and two-photon absorption characteristics of the title dyes have also been investigated by using density functional theory (DFT) and the structure-property relationships are discussed. The TPA cross sections calculated by means of quadratic response time-dependent DFT using the Coulomb-attenuated CAM-B3LYP functional support the experimentally observed trends within the series, as well as higher delta(TPA) values of the title compounds compared to those of analogous fluorene or carbazole-derived dyes. In contrast, the traditional B3LYP functional was not successful in predicting the observed trend of TPA cross sections for systems with different central cores. In general, structural modification of the pi-bridge composition by replacement of ethynylene (alkyne) with E-ethenylene (alkene) linkages and/or replacement of dialkylamino electron-donating edge substituents by diarylamino ones results in an increase of delta(TPA) values. The combination of large TPA cross sections and high emission quantum yields makes the title benzothiazole-based dyes attractive for applications involving two-photon excited fluorescence (TPEF).
一系列新型杂环基染料具有供体-π-桥-受体-π-桥-供体（D-π-A-π-D）结构特征，其中苯并噻唑作为吸电子核心，通过钯催化的 Sonogashira 和 Suzuki 型交叉偶联反应设计和合成。所有目标发色团都表现出强烈的单光子和双光子激发发射。具有二苯胺基官能团的制备衍生物的最大双光子吸收（TPA）截面 delta(TPA)在 760 至 800nm 的波长范围内发生，约为 900-1100 GM。还通过使用密度泛函理论（DFT）研究了标题染料的单光子和双光子吸收特性，并讨论了结构-性质关系。使用库仑衰减 CAM-B3LYP 功能的二次响应时变 DFT 计算的 TPA 截面支持了该系列中观察到的趋势，以及标题化合物的 delta(TPA)值高于类似芴或咔唑衍生染料的值。相比之下，传统的 B3LYP 功能在预测具有不同中心核的系统的 TPA 截面观察到的趋势方面并不成功。一般来说，通过用 E-乙烯基（烯烃）取代乙炔基（炔）以及/或用二芳基氨基供电子边缘取代基取代二烷基氨基来修饰π-桥组成，会导致 delta(TPA)值增加。大的 TPA 截面和高的发射量子产率的组合使得基于苯并噻唑的标题染料在涉及双光子激发荧光（TPEF）的应用中具有吸引力。
