Razavi Sayed Ali Akbar, Masoomi Mohammad Yaser, Morsali Ali
Department of Chemistry, Faculty of Sciences, Tarbiat Modares University , P.O. Box 14117-13116, Tehran, Islamic Republic of Iran.
Inorg Chem. 2017 Aug 21;56(16):9646-9652. doi: 10.1021/acs.inorgchem.7b01155. Epub 2017 Aug 4.
To design a robust, π-conjugated, low-cost, and easy to synthesize metal-organic framework (MOF) for cation sensing by the photoluminescence (PL) method, 4,4'-oxybis(benzoic acid) (HOBA) has been used in combination with 3,6-di(pyridin-4-yl)-1,2,4,5-tetrazine (DPT) as a tetrazine-functionalized spacer to construct [Zn(OBA)(DPT)]·DMF (TMU-34(-2H)). The tetrazine motif is a π-conjugated, water-soluble/stable fluorophore with relatively weak σ-donating Lewis basic sites. These characteristics of tetrazine make TMU-34(-2H) a good candidate for cation sensing. Because of hydrogen bonding between tetrazine moieties and water molecules, TMU-34(-2H) shows different PL emissions in water and acetonitrile. Cation sensing in these two solvents revealed that TMU-34(-2H) can selectively detect Hg in water (by 243% enhancement) and in acetonitrile (by 90% quenching). The contribution of electron-donating/accepting characteristics along with solvation effects on secondary interactions of the tetrazine motifs inside the TMU-34(-2H) framework results in different signal transductions. Improved sensitivity and accuracy of detection were obtained using the double solvent sensing method (DSSM), in which different signal transductions of TMU-34(-2H) in water and acetonitrile were combined simultaneously to construct a double solvent sensing curve and formulate a sensitivity factor. Calculation of sensitivity factors for all of the tested cations demonstrated that it is possible to detect Hg by DSSM with ultrahigh sensitivity. Such a tremendous distinction in the Hg sensitivity factor is visualizable in the double solvent sensing curve. Thus, by application of DSSM instead of one-dimensional sensing, the interfering effects of other cations are completely eliminated and the sensitivity toward Hg(II) is highly improved. Strong interactions between Hg and the nitrogen atoms of the tetrazine groups along with easy accessibility of Hg to the tetrazine groups lead to a shorter response time (15 s) in comparison with other MOF-based Hg sensors.
为了设计一种坚固、π共轭、低成本且易于合成的用于通过光致发光（PL）方法进行阳离子传感的金属有机框架（MOF），4,4'-氧代双苯甲酸（HOBA）已与3,6-二（吡啶-4-基）-1,2,4,5-四嗪（DPT）结合用作四嗪功能化间隔基，以构建[Zn（OBA）（DPT）]·DMF（TMU-34（-2H））。四嗪基序是一种π共轭、水溶性/稳定的荧光团，具有相对较弱的给σ电子的路易斯碱性位点。四嗪的这些特性使TMU-34（-2H）成为阳离子传感的良好候选物。由于四嗪部分与水分子之间存在氢键，TMU-34（-2H）在水和乙腈中表现出不同的PL发射。在这两种溶剂中的阳离子传感表明，TMU-34（-2H）可以在水中（增强243%）和乙腈中（猝灭90%）选择性地检测汞。供电子/吸电子特性以及溶剂化效应对TMU-34（-2H）框架内四嗪基序二级相互作用的影响导致不同的信号转导。使用双溶剂传感方法（DSSM）获得了更高的检测灵敏度和准确性，其中TMU-34（-2H）在水和乙腈中的不同信号转导同时结合起来构建双溶剂传感曲线并制定灵敏度因子。对所有测试阳离子的灵敏度因子计算表明，通过DSSM可以超高灵敏度检测汞。汞灵敏度因子的这种巨大差异在双溶剂传感曲线中是可见的。因此，通过应用DSSM而非一维传感，其他阳离子的干扰效应被完全消除，并且对Hg（II）的灵敏度得到了极大提高。与其他基于MOF的汞传感器相比，汞与四嗪基团的氮原子之间存在强相互作用，并且汞易于接近四嗪基团，导致响应时间更短（15秒）。
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