Utilizing flexible bis(tridentate)polypyridyl ligands, the two new luminescent 2D metal organic frameworks {Zn₂(tpbn)(2,6-NDC)₂}_n (1) and {[Zn₂(tphn)(2,6-NDC)₂]·4H₂O}_n (2), where tpbn = N,N′,N″,N‴-tetrakis(2-pyridylmethyl)-1,4-diaminobutane, tphn = N,N′,N″,N‴-tetrakis(2-pyridylmethyl)-1,6-diaminohexane, and 2,6-H₂NDC = 2,6-naphthalenedicarboxylic acid, have been isolated in good yields under solvothermal conditions. Their solid-state molecular structures have been determined by single-crystal X-ray diffractometry. Both 1 and 2 have pentacoordinated Zn(II) centers with an N₃O₂ environment from three nitrogen atoms of the tpbn or tphn ligand and two carboxylate oxygen atoms from two different 2,6-NDC linkers. However, the binding modes of the tridentate part of polypyridyl ligands to the Zn(II) center are different in 1 and 2—meridional (tpbn) vs facial (tphn) due to an increase (1.5 times) in the methylene chain length. Thus, the binding mode of 2,6-NDC to the Zn(II) center differs: bis(monodentate) syn-anti in 1 and bis(monodentate) syn-syn in 2. This difference in binding modes of the components has a profound effect on the conformation of the six-membered ring (metal centers are considered as the vertices in it) within the 2D framework: honeycomb vs chair form for 1 and 2, respectively. In addition to further characterization by elemental analysis and UV–vis and FT-IR spectroscopy, their framework stabilities in water and thermal properties have been studied by powder X-ray diffraction and thermogravimetric analysis, respectively. On the basis of thermodiffractometry, 1 and 2 retain their crystallinity and overall structure up to 350 and 325 °C, respectively. Their luminescent properties have been utilized to demonstrate sensing of various solvents as well as nitro-aromatic compounds in water, which correlate well with their structural differences. Through the spectral overlap, lifetime measurements, and nature of the Stern–Volmer plots, the fluorescence quenching pathway for the nitro-analytes, particularly 2,4,6-trinitrophenol (TNP), is established for 1 and 2. Their recyclability and stability after sensing experiments are found to be excellent.

中文翻译：

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中性发光金属有机骨架：结构多样化，光物理性质和传感应用

利用灵活的双（三齿）聚吡啶基配体，两个新的发光二维金属有机骨架{Zn ₂（tpbn）（2,6-NDC）₂ } _n（1）和{[Zn ₂（tphn）（2,6-NDC） ）₂ ]·4H ₂ ö} _ñ（2），其中tpbn = ñ，ñ '，ñ “，ñ '''，N'-四（2-吡啶基甲基）-1,4-二氨基丁烷，tphn = ñ，ñ '，ñ ”，N ‴-四（2-吡啶基甲基）-1,6-二氨基己烷和2,6-H ₂NDC = 2,6-萘二甲酸，已在溶剂热条件下以高收率分离出。它们的固态分子结构已经通过单晶X射线衍射法确定。既1和2已经五配位的Zn（II）与N-中心₃ ö ₂从tpbn或tphn配体和两个羧基的氧原子的三个氮原子的环境从两个不同的2,6-NDC接头。但是，聚吡啶基配体的三齿部分与Zn（II）中心的结合方式在1和2由于亚甲基链长的增加（1.5倍），子午线（tpbn）与脸部（tphn）的关系。因此，2，6-NDC与Zn（II）中心的结合方式不同：bis（单齿）syn-anti为1，而bis（单齿）syn-syn为2。组件的绑定方式上的这种差异对二维框架内六元环的构型（金属中心被视为其中的顶点）产生了深远的影响：1和2的蜂窝与椅子形式， 分别。除了通过元素分析，紫外可见光谱和FT-IR光谱进一步表征外，还分别通过粉末X射线衍射和热重分析研究了它们在水和热性质中的骨架稳定性。根据热衍射法，1和2分别保持最高350和325°C的结晶度和整体结构。它们的发光特性已被用来证明对水中各种溶剂以及硝基芳族化合物的感测，这与它们的结构差异具有很好的相关性。通过光谱重叠，寿命测量和Stern-Volmer图的性质，针对1和2建立了硝基分析物，尤其是2,4,6-三硝基苯酚（TNP）的荧光猝灭途径。发现它们在感测实验后具有良好的可回收性和稳定性。