Water-soluble distyrylbenzene-based aldehydes are excellent fluorescence turn-on indicators for amine detection, since they are themselves non-fluorescent in water. Here, the fluorescence quenching mechanisms of aldehydes with systematically increasing $\pi$-systems are investigated in an aqueous environment using quantum chemical methods. Although the aldehydes are structurally related, with each extension of the $\pi$-system the fluorescence quenching mechanism changes from excited-state hydrogen transfer to trans→cis isomerization and n${\pi }^{\ast }$ state-mediated intersystem crossing, until the aldehydes become fluorescent in water. For distyrylbenzene aldehyde, n${\pi }^{\ast }$ mediated ISC has been identified as major fluorescence quenching channel, which becomes closed upon reaction with an amine explaining its fluorescence turn-on sensitivity.

水溶性的基于二苯乙烯基苯的醛是用于胺检测的出色的荧光开启指示剂，因为它们本身在水中是无荧光的。在此，醛的荧光猝灭机理随着系统地增加$\pi$-系统是在水环境中使用量子化学方法研究的。尽管醛在结构上相关，但随着$\pi$-系统的荧光猝灭机理从激发态氢转移到反式→顺式异构化和n${\pi }^{\ast }$状态介导的系统间交叉，直到醛在水中发荧光为止。对于二苯乙烯基苯醛，n${\pi }^{\ast }$ 介导的ISC已被鉴定为主要的荧光猝灭通道，与胺反应后被封闭，从而说明了其荧光开启敏感性。