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Using Click Chemistry to Tune the Properties and the Fluorescence Response Mechanism of Structurally Similar Probes for Metal Ions

机译:使用单击化学来调节结构相似的金属离子探针的性质和荧光响应机理

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Four cyclam-based fluorescent molecular probes were prepared using click chemistry and investigated to determine the effect of the triazole connectivity and fluorophore substitution on the photophysical properties and metal-ion response mechanism. The fluorescence of the ligands is turned on in the presence of Zn-II but varies in intensity depending on the solvent; the highest signal changes are found in MeCN. Complexation with Cu-II leads to fluorescence quenching, but only in the aqueous solvent, in which the triazole is involved in coordination of the metal. The length of the pendant triazole arm influences the ligand field around pentacoordinate Cu-II to yield a distorted square-planar coordination geometry in the ligands with an ethylene linker. The quantum yield (QY) of the emission intensity can be tuned by the triazole substitution, thereby resulting in increases in QY of more than one order of magnitude (ligand 1 versus 3). Changing the fluorophore opens up alternative radiative processes, thus leading to phosphorescence-like behavior in coumarin probe 2. Steady-state fluorescence emission spectra of the free ligands and their respective Cu-II complexes in a glass environment reveal two different inherent fluorescence quenching mechanisms. In the free ligands an electron-transfer deactivates the excited chromophore, whereas in the Cu-II complexes it is energy transfer that results in complete quenching of the emission of the ligands.
机译:使用点击化学方法制备了四种基于Cyclam的荧光分子探针,并进行了研究以确定三唑连接性和荧光团取代对光物理性质和金属离子响应机理的影响。在Zn-II的存在下,配体的荧光会开启,但强度会因溶剂而异;在MeCN中发现信号变化最大。与Cu-II的络合会导致荧光猝灭,但仅在水性溶剂中发生,其中三唑参与金属的配位。三唑悬垂臂的长度影响五配位Cu-II周围的配体场,从而在带有乙烯接头的配体中产生扭曲的方平面配位几何形状。可以通过三唑取代来调节发射强度的量子产率(QY),从而导致QY的增加幅度超过一个数量级(配体1对3)。改变荧光团打开了替代的辐射过程,从而导致香豆素探针2中的磷光行为。游离配体及其各自的Cu-II络合物在玻璃环境中的稳态荧光发射光谱显示出两种不同的固有荧光猝灭机制。在游离配体中,电子转移使激发的发色团失活,而在Cu-II络合物中,正是能量转移导致配体的发射完全淬灭。

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