Nishikawa Kai, Ubukata Takashi
Department of Chemistry and Life Science, Graduate School of Engineering Science, Yokohama National University, 79-5, Tokiwadai, Hodogaya, Yokohama, Kanagawa, 240-8501, Japan.
Faculity of Engineering, Yokohama National University, 79-5, Tokiwadai, Hodogaya, Yokohama, Kanagawa, 240-8501, Japan.
Photochem Photobiol Sci. 2025 Sep 7. doi: 10.1007/s43630-025-00774-z.
In recent years, fluorescence-switchable molecules have garnered significant attention as fluorescent dyes for super-resolution fluorescence microscopy, which is increasingly demanded in the field of biochemical imaging. Among such molecules, diarylethene-S,S,S',S'-tetraoxide derivatives have proven particularly promising due to their ability to achieve high contrast fluorescence switching. Diarylethenes incorporating perfluorocyclopentene as the ethene bridge have become the standard scaffold due to their excellent fatigue resistance and thermal stability. However, their inherently low polarity necessitates extensive functionalization with hydrophilic groups to render them suitable for use in aqueous environments, such as in fluorescent labeling for super-resolution fluorescence microscopy. To address this limitation, we designed a novel class of oxidized diarylmaleimide (DAM) derivative featuring a maleimide as the ethene moiety, offering increased polarity and synthetic flexibility. Specifically, DAM 1, composed of 2,4-dimethyl-5-phenylthiophene and N-methylmaleimide, and its oxidized counterpart DAM 2, bearing two S,S-dioxidized thiophene rings, were synthesized and characterized. DAM 1 exhibited reversible photochromism upon irradiation with 436-nm and 550-nm light, accompanied by weak turn-off fluorescence and a cyclization quantum yield that depended strongly on solvent polarity. In contrast, DAM 2 exhibited two types of photoisomerization, one-way and partial two-way, depending on the polarity of the solvent, and exhibited turn-on fluorescence behavior. These findings suggest that DAM-based systems can be promising alternatives to conventional perfluorocyclopentene-based diarylethenes for aqueous fluorescence imaging applications, due to their high polarity compared to them and tunable-photoresponsive properties.
近年来，荧光可切换分子作为用于超分辨率荧光显微镜的荧光染料备受关注，这在生化成像领域的需求日益增加。在这类分子中，二芳基乙烯 - S,S,S',S'-四氧化物衍生物因其能够实现高对比度荧光切换而被证明特别有前景。以全氟环戊烯作为乙烯桥的二芳基乙烯由于其出色的抗疲劳性和热稳定性已成为标准支架。然而，它们固有的低极性需要用亲水性基团进行广泛的功能化，以使它们适用于水性环境，例如用于超分辨率荧光显微镜的荧光标记。为了解决这一限制，我们设计了一类新型的氧化二芳基马来酰亚胺（DAM）衍生物，其以马来酰亚胺作为乙烯部分，具有更高的极性和合成灵活性。具体而言，合成并表征了由2,4 - 二甲基 - 5 - 苯基噻吩和N - 甲基马来酰亚胺组成的DAM 1及其带有两个S,S - 二氧化噻吩环的氧化对应物DAM 2。DAM 1在436 - nm和550 - nm光照射下表现出可逆光致变色，伴随着较弱的荧光猝灭以及强烈依赖于溶剂极性的环化量子产率。相比之下，DAM 2根据溶剂的极性表现出两种类型的光异构化，单向和部分双向，并表现出荧光开启行为。这些发现表明，基于DAM的体系由于其相对于传统全氟环戊烯基二芳基乙烯具有更高的极性和可调光响应特性，在水性荧光成像应用中可能是有前途的替代品。
