A novel catechol based dipodal fluorescent chelator N,N′-bis[3-[(E)-(2,3-dihydroxyphenyl)methyleneamino]propyl]propanediamide(MPC), has been developed and its photophysical behaviour was studied by experimental (UV-VIS and fluorescence) and DFT method. The design of the molecule has been inspired from the naturally occurring siderophore enterobactin, a catechol based chelator with amide linkage, that shows an excellent binding efficiency towards Fe(III). The dipodal molecule (MPC) presented here, carries two catechol pendant binding moieties linked to the malonate central unit through propylene spacers by amide linkage. MPC showed good selectivity for Fe(III) at 10⁻⁴ M concentration in aqueous medium amongst the biologically and environmentally important metal ions chosen viz., Na(I), K(I), Al(III), Cr(III), Fe(III), Fe(II), Co(II), Ni(II), Cu(II), and Zn(II), by demonstrating a remarkable quenching in the fluorescent emission from 262 a.u. to 55 a.u. at λ_max = 477 nm. Also, the pre-organized assembled ligand favored an efficient Fe (III) encapsulation through coordination by imine nitrogen and catecholate oxygen donors. High formation constant (log β = 31.3) for 1:1 metal–ligand complex evaluated by both potentiometric and spectrophotometric methods, established the strong binding efficiency of the ligand for Fe(III) metal ion. The binding stoichiometry in the complex was also confirmed from Stern –Volmer and Hill Plot analysis. Further investigation on the emission behavior of MPC in a completely DMSO system explored its suitability for extensive applications in the areas such as, metallurgy, material science, iron contamination remedial in the materials etc.. DFT studies suggest that the ligand displays a U-shaped geometry with a parallel π-stacking and the hydrogen bond between two arms. The experimental infrared, electronic, fluorescence, ¹H nmr, ¹³C nmr spectra were correlated with the theoretical results. The nature of electronic transitions were identified from the TDDFT calculation. The ligand forms a hexa-coordinated complex with six Fe-O bonds extending an orthorhombic geometry due distortion from a regular octahedron.

中文翻译：

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基于儿茶酚的多功能双足螯合剂的光物理研究：光学探针在 Fe(III) 选择性检测中的应用。

开发了一种基于儿茶酚的新型双足荧光螯合剂 N,N'-双[3-[(E)-(2,3-二羟基苯基)亚甲基氨基]丙基]丙二胺(MPC), 并通过实验 (UV) 研究了其光物理行为-VIS 和荧光）和 DFT 方法。该分子的设计灵感来自天然存在的铁载体肠杆菌素，这是一种带有酰胺键的基于儿茶酚的螯合剂，对 Fe(III) 显示出出色的结合效率。这里介绍的双足分子 (MPC) 带有两个儿茶酚悬垂结合部分，通过酰胺键通过丙烯间隔基连接到丙二酸中心单元。^{MPC 在 10 -4}时显示出对 Fe(III) 的良好选择性 水介质中的 M 浓度在选定的生物和环境重要金属离子中，即 Na(I)、K(I)、Al(III)、Cr(III)、Fe(III)、Fe(II)、Co(II) )、Ni(II)、Cu(II) 和 Zn(II)，通过证明在 λ _max下从 262 au 到 55 au 的荧光发射显着猝灭 = 477 纳米。此外，预先组织的组装配体通过亚胺氮和儿茶酚氧供体的协调有利于有效的 Fe (III) 封装。通过电位法和分光光度法评估的 1:1 金属-配体络合物的高形成常数 (log β = 31.3)，确定了配体对 Fe(III) 金属离子的强结合效率。Stern-Volmer 和 Hill Plot 分析也证实了复合物中的结合化学计量。进一步研究 MPC 在完全 DMSO 体系中的发射行为，探索其在冶金、材料科学、材料中铁污染修复等领域的广泛应用的适用性。DFT 研究表明配体呈 U 形具有平行 π 堆叠和两个臂之间的氢键的几何结构。¹ H nmr、¹³ C nmr谱与理论结果相关。电子跃迁的性质是从 TDDFT 计算中确定的。由于正八面体的变形，配体形成具有六个 Fe-O 键的六配位络合物，延伸出正交几何结构。