Jiménez-Sánchez Arturo, Ortíz Benjamín, Ortiz Navarrete Vianney, Farfán Norberto, Santillan Rosa
Departamento de Química, Centro de Investigación y de Estudios Avanzados del IPN, CINVESTAV, Apdo., Postal 14-740, México, D. F. 07000, México.
Analyst. 2015 Sep 7;140(17):6031-9. doi: 10.1039/c5an00789e.
Two simple and low cost 2,4-di-tert-butyl-6-[(1-hydroxycyclohexylmethylimino)methyl]phenol (L1) and 2-[{(1-hydroxycyclohexyl)methylimino}methyl]phenol (L2) Schiff base sensors exhibiting selectivity for Zn(2+) in water:methanol (95:5, v/v, 10 mM HEPES) are described. L1 and L2 display an "off-on" fluorescence effect forming the L1·Zn and L2·Zn complexes, respectively. In the case of L1·Zn, the emission response is quenched by the addition of Cu(2+) forming the respective L1·Cu complex; in spite of that, the fluorescence signal can be completely restored only by the addition of tartrate anions (C4H4O6(2-)) forming again L1·Znvia the "off-on" displacement approach. However, in the case of L2·Zn no Cu(2+) interference is observed, which is a typical problem for Zn(2+) sensors. Here we describe that a very subtle structural change in the ligand during transition from the enol-imine tautomer in L1 to the keto-enamine tautomer in L2 is enough to modulate the Zn(2+)/Cu(2+) selectivity. Also, the Zn(2+)vs. Cd(2+) discrimination for L1 and L2 is proved. Moreover, we found that the interaction between both L·Zn complexes and tartrate anions completely restored the free ligands by the ligand substitution mechanism even in a more efficient association than phosphate anions. Further, a second colorimetric response channel upon addition of Fe(2+) was observed for L1 and L2. Then, TD-DFT theoretical calculations were conducted in order to study the efficiency of the sensors to give different responses in the presence of such metal ions. Finally, the L2 sensor successfully detects Zn(2+) in Jurkat cells cultured with and without Zn(2+) enriched medium.
本文描述了两种简单且低成本的席夫碱传感器，即2,4 - 二叔丁基 - 6 - [(1 - 羟基环己基甲基亚氨基)甲基]苯酚（L1）和2 - [{(1 - 羟基环己基)甲基亚氨基}甲基]苯酚（L2），它们在水：甲醇（95:5，v/v，10 mM HEPES）中对Zn(2+)具有选择性。L1和L2分别形成L1·Zn和L2·Zn配合物时呈现“关 - 开”荧光效应。对于L1·Zn，加入Cu(2+)形成相应的L1·Cu配合物会淬灭发射响应；尽管如此，仅通过加入酒石酸根阴离子（C4H4O6(2-)），通过“关 - 开”置换方法再次形成L1·Zn，荧光信号就能完全恢复。然而，对于L2·Zn，未观察到Cu(2+)干扰，这是Zn(2+)传感器的一个典型问题。在此我们描述，从L1中的烯醇 - 亚胺互变异构体转变为L2中的酮 - 烯胺互变异构体时，配体中非常细微的结构变化足以调节Zn(2+)/Cu(2+)选择性。此外，还证明了L1和L2对Zn(2+)与Cd(2+)的区分能力。而且，我们发现两种L·Zn配合物与酒石酸根阴离子之间的相互作用通过配体取代机制完全恢复了游离配体，甚至比磷酸根阴离子的结合更有效。此外，对于L1和L2，加入Fe(2+)时观察到了第二个比色响应通道。然后，进行了TD - DFT理论计算，以研究传感器在这些金属离子存在下产生不同响应的效率。最后，L2传感器成功检测了在添加和未添加富含Zn(2+)培养基培养的Jurkat细胞中的Zn(2+)。
