Department of Chemistry, Tamralipta Mahavidyalaya, Tamluk 721636, West Bengal, India; Department of Applied Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand 826004, India.
Department of Applied Chemistry, Indian Institute of Technology (Indian School of Mines), Dhanbad, Jharkhand 826004, India.
Spectrochim Acta A Mol Biomol Spectrosc. 2021 Jun 5;254:119612. doi: 10.1016/j.saa.2021.119612. Epub 2021 Feb 23.
Two new dicyanamide bridged multinuclear Zn complexes, [Zn(L)(µ-dca)(µ-dca)] (1) and [Zn(L)(µ-dca)(µ-dca)] (2) have been synthesized using NO-based pro-ligands (HL = N,N'-bis(5-bromo-3-methoxysalicylidenimino)-1,3-diaminopropane, HL = N,N'-bis(3-ethoxysalicylidene)-2,2-dimethyl-1,3-propanediamine) and characterized by microanalytical and spectroscopic techniques. Both complexes are stable in solution and solid-state. Thermogravimetric analysis (TGA) findings showed that complexes are stable at room temperature. Single-crystal X-ray diffraction (SCXRD) has proven that complexes are identical structures where two zinc metal ions are crystallographically independent. The directional properties of dicyanamide co-ligands via µ bridging have resulted in different connectivity of zinc metal ions leading to 1D templates. SCXRD revealed some notable non-covalent interactions (π⋯π, C-H····π, and H-bonding) in their solid-state crystal structures. 1-2 have strong fluorescence behaviour over pro-ligands, which may be quenched in the presence of various electron-deficient explosive nitroaromatic compounds (epNACs). Complex 2 fluorescence intensity is sharper than 1; hence the former retained high sensitivity and selectivity for trinitrophenol (TNP). The enhancement of fluorescence mechanism, detection limit (LOD), and the quenching constant (K) have been calculated using the Stern-Volmer equation (SV), where the K value for TNP is found to be 1.542 × 10 M. The solution phase quenching mechanism has been rationalized by (a) electrostatic interactions through charge-transfer complex, (b) photo-induced electron transfer (PET) by the HOMO-LUMO energy gap via DFT, and (c) fluorescence resonance energy transfer (FRET). Finally, complex 2 is applied as a sensor by turn-off fluorescence response to detecting TNP nitroaromatics in the DMF medium.
使用基于 NO 的前配体（HL = N，N'-双（5-溴-3-甲氧基水杨醛亚氨基）-1,3-二氨基丙烷，HL = N，N'-双（3-乙氧基水杨醛亚胺基）-2,2-二甲基-1,3-丙二胺）合成了两个新的二氰胺桥联多核 Zn 配合物，[Zn(L)(µ-dca)(µ-dca)]（1）和[Zn(L)(µ-dca)(µ-dca)]（2），并通过微量分析和光谱技术进行了表征。两种配合物在溶液中和固态中均稳定。热重分析（TGA）结果表明，配合物在室温下稳定。单晶 X 射线衍射（SCXRD）证明了配合物具有相同的结构，其中两个锌金属离子在晶体学上是独立的。二氰胺共配体通过µ桥的方向性导致锌金属离子的不同连接，形成 1D 模板。SCXRD 揭示了它们在固态晶体结构中存在一些显著的非共价相互作用（π⋯π、C-H····π 和氢键）。1-2 对前配体具有较强的荧光行为，在存在各种缺电子爆炸硝基芳烃化合物（epNACs）时可能会被猝灭。与前配体相比，2 的荧光强度更强；因此，前者对三硝基苯酚（TNP）保持了较高的灵敏度和选择性。荧光增强机制、检测限（LOD）和猝灭常数（K）已通过 Stern-Volmer 方程（SV）进行了计算，其中 TNP 的 K 值为 1.542×10^-4 M。通过（a）通过电荷转移络合物的静电相互作用，（b）通过 DFT 通过 HOMO-LUMO 能量间隙的光诱导电子转移（PET），以及（c）荧光共振能量转移（FRET），对溶液相猝灭机制进行了合理化。最后，通过关闭荧光响应，2 被用作传感器，以在 DMF 介质中检测 TNP 硝基芳烃。
