Departamento de Química Orgánica y Fisicoquímica, Facultad de Ciencias Químicas y Farmacéuticas, Universidad de Chile, Santiago, Chile.
Institut Químic de Sarrià, Universitat Ramon Llull, Barcelona, Spain.
PLoS One. 2018 Jul 2;13(7):e0200006. doi: 10.1371/journal.pone.0200006. eCollection 2018.
In this study, we report the synthesis and the photochemical behavior of a series of new "click-on" fluorescent probes designed to detect singlet oxygen. They include a highly fluorescent chemical structure, an aryloxazole ring, linked to a furan moiety operating as singlet oxygen trap. Their activity depends on both the structure of the aryloxazole fluorophore and the electron-donating and electron-accepting properties of the substituents attached to the C-5 of the furan ring. All probes are selectively oxidized by singlet oxygen to give a single fluorescent product in methanol and produce negligible amounts of singlet oxygen themselves by self-sensitization. The most promising dyad, (E)-2-(2-(5-methylfuran-2-yl)vinyl)naphtho[1,2-d]oxazole, FN-6, shows outstanding reactivity and sensitivity: it traps singlet oxygen with a rate constant (5,8 ± 0.1) x 1(07) M-1 s-1 and its fluorescence increases by a factor of 500 upon reaction. Analysis of the dyads reactivity in terms of linear free energy relationships using the modified Swain and Lupton parameter F and the Fukui condensed function for the electrophilic attack, suggests that cycloaddition of singlet oxygen to the furan ring is partially concerted and possibly involves an exciplex with a "more open" structure than could be expected for a concerted cycloaddition.
在这项研究中，我们报告了一系列新的“点击式”荧光探针的合成和光化学行为，这些探针旨在检测单线态氧。它们包括一个高度荧光的化学结构，一个芳基恶唑环，与作为单线态氧陷阱的呋喃部分相连。它们的活性取决于芳基恶唑荧光团的结构以及连接到呋喃环 C-5 上的取代基的供电子和吸电子性质。所有探针都被单线态氧选择性氧化，在甲醇中产生单一荧光产物，并且通过自身敏化产生可忽略量的单线态氧。最有前途的偶联物，（E）-2-（2-（5-甲基呋喃-2-基）乙烯基）萘并[1,2-d]恶唑，FN-6，表现出出色的反应性和灵敏度：它以（5,8 ± 0.1) x 1(07) M-1 s-1 的速率常数捕获单线态氧，并且反应后其荧光强度增加了 500 倍。根据线性自由能关系使用改进的 Swain 和 Lupton 参数 F 和亲电攻击的 Fukui 凝聚函数分析偶联物的反应性表明，单线态氧与呋喃环的环加成部分是协同的，并且可能涉及与协同环加成相比具有“更开放”结构的激发态复合物。
