摘要/Abstract

在四苯基甲烷外侧通过C=C双键引入四个N-甲基-4-苯基吡啶盐片段，合成了一个新的全共轭单体T-1.其在水中与2 equiv.的葫芦脲[8]结合，形成了新的高强荧光的超分子有机框架SOF-r-SPP.动态光散射实验表明，在T-1浓度为1.0和0.031 mmol/L时，SOF-r-SPP的流体力学直径分别为68和41 nm.粉末X-射线衍射实验揭示，SOF-r-SPP形成孔径为2.3 nm的三维金刚石型周期性结构.硝基苯衍生物能有效淬灭SOF-r-SPP的荧光.在17个研究的硝基苯类分子中，苦味酸的淬灭效率最高. SOF-r-SPP作为荧光传感器，对苦味酸的检测极限可以达到0.024 mmol/L.
关键词: 超分子有机框架, 荧光传感, 苦味酸, 葫芦[8]脲, 自组装
Cucurbit[8]uril (CB[8])-encapsulation-based host-guest chemistry has been utilized to construct supramolecular organic frameworks, a family of water-soluble, self-assembled periodic porous structures, from multi-armed preorganized building blocks. The tetrahedral prototype building block has been incorporated with four CH₂ units to connect the central tetraphenylmethane and appended aromatic arms. Herein we designed and prepared a new fully conjugated tetrahedral building block T-1, which possesses four N-methyl 4-(4-styrylphenyl)pyridinium (SPP) arms. The 1:2 mixture of T-1 with CB[8] in water leads to the formation of a new three-dimensional homogeneous diamondoid supramolecular organic framework SOF-r-SPP through CB[8] encapsulation for intermolecular dimers of the appended SPP units. ¹H NMR, absorption and fluorescence experiments conformed strong binding between the two components at diluted concentrations and 1:2 binding stoichiometry. Isothermal calorimetric (ITC) experiments established that the three-component (SPP)₂ÌCB[8] complexes formed between the SPP units of T-1 and CB[8] had an apparent binding constant of 5.5×10¹³ M^-2, which was 5.5×10⁴ times as high as that of the complex of a SPP control. ITC experiments also revealed that the self-assembly of SOF-r-SPP are driven both enthalpically and entropically, but the enthalpic contribution was overwhelmingly higher. Dynamic light scattering experiments revealed that within the concentration range of 0.031 mmol/L to 1.0 mmol/L of T-1, the framework possessed a hydrodynamic diameter of 41 nm to 68 nm. Molecular modelling study indicated that the new regular framework formed an aperture of 2.3 nm. Although T-1 has nearly no fluorescence, SOF-r-SPP exhibits strong fluorescence in water probably due to the encapsulation of the SPP dimers by CB[8] that suppresses the relative rotation of the aromatic rings. Adding nitrobenzene or naphthalene derivatives to the solution of SOF-r-SPP remarkably quenched the fluorescence of the framework. Among other sixteen nitro-bearing aromatic molecules, picric acid (2,4,6-trinitrophenol) exhibited the largest quenching ability. At the low concentration of 1.0 μmol/L for T-1 of SOF-r-SPP, 0.1 μmol/L of 2,4,6-tirnitrophenol could cause 16% quenching of the fluorescence of SOF-r-SPP and 0.1 mmol/L of 2,4,6-tirnitrophenol could realize nearly complete quench (>97%). Following a reported method, the limit of detection of SOF-r-SPP for picric acid was as low as 0.024 μmol/L.
Key words: supramolecular organic framework, fluorescence sensing, 2,4,6-trinitrophenol, cucurbituril, self-assembly


PDF全文下载地址:

点我下载PDF