Department of Chemistry, National Taiwan University, Taipei, Taiwan 10617.
Photochem Photobiol Sci. 2014 Feb;13(2):211-23. doi: 10.1039/c3pp50196e.
To understand the effect of iptycene scaffolds on the locally excited (LE) and intramolecular charge transfer (ICT) fluorescence of aminobenzonitriles, a series of triptycene and pentiptycene derivatives were synthesized and their molecular structures and photophysical properties were characterized and compared with the parent phenylene systems, 4-(N-methylamino)benzonitrile (MABN), 4-(N,N-dimethylamino)benzonitrile (DMABN), and 4-(N-phenylamino)benzonitrile (PABN). The iptycene effect does not change the nature of the fluorescing states for each amino donor system, i.e., the MA, PA, and DMA series display LE-only, ICT-only, and LE-ICT dual fluorescences, respectively. However, the iptycene scaffolds impose a significant modification of the absorption and emission spectra, fluorescence quantum efficiency and lifetimes, and the interplay of LE and ICT states. The observed iptycene effect has been discussed with three factors: (1) steric effect on increasing the amino twist angle, (2) steric shielding of solvation to the aminobenzonitrile core, and (3) hyperconjugation interactions of the aminobenzonitrile core with the peripheral phenylene groups of iptycene.
为了理解茚并骨架对氨基苯甲腈的局域激发（LE）和分子内电荷转移（ICT）荧光的影响，合成了一系列三茚和五茚衍生物，并对其分子结构和光物理性质进行了表征，并与母体亚苯基体系、4-（N-甲基氨基）苯甲腈（MABN）、4-（N，N-二甲基氨基）苯甲腈（DMABN）和 4-（N-苯基氨基）苯甲腈（PABN）进行了比较。茚并骨架的影响并没有改变每个氨基供体体系的荧光状态的本质，即 MA、PA 和 DMA 系列分别显示仅 LE、仅 ICT 和 LE-ICT 双重荧光。然而，茚并骨架对吸收和发射光谱、荧光量子效率和寿命以及 LE 和 ICT 状态的相互作用产生了显著的修饰。观察到的茚并效应可以用三个因素来解释：（1）增加氨基扭转角的空间位阻效应，（2）对氨基苯甲腈核心的溶剂化的空间位阻屏蔽，以及（3）氨基苯甲腈核心与茚并的外围亚苯基基团的超共轭相互作用。
