Synthesis of bifunctional biscatecholamine chelators for uranium decorporation

Bis-Catecholamide-Based Materials for Uranium Extraction

This work reports the synthesis of formo-phenolic resins containing four catecholamide (CAM) moieties with admixture of phenol, catechol or resorcinol. These chelating resins have been developed to selectively extract U(VI) from seawater. This media is a challenging environment due to a pH around 8.2 and a large excess of alkaline and earth-alkaline cations. From the various sorption experiments investigated, the results indicate that the synthesized material exhibit good sorbent properties for U(VI) with uptake capacity about 50 mg/g for the more promising resins with a pronounced selectivity for uranium even under saline conditions. Thermodynamic and kinetic adsorption data were determined for the best resin (Langmuir adsorption model and pseudo-second order model).

Formation of a tris(catecholato) iron(III) complex with a nature-inspired cyclic peptoid ligand

Siderophore-mimicking macrocyclic peptoids were synthesized. Peptoid 3 with intramolecular hydrogen bonds showed an optimally arranged primary coordination sphere leading to a stable catecholate-iron complex. The tris(catecholato) structure of 3-Fe(iii) was determined with UV-vis, fluorescence, and EPR spectroscopies and DFT calculations. The iron binding affinity was comparable to that of deferoxamine, with enhanced stability upon air exposure.

Peptoid-based siderophore mimics as dinuclear Fe3+ chelators

A practical synthesis of preorganized tripodal enterobactin/corynebactin-type ligands (consisting of a C₃-symmetric macrocyclic peptoid core, three catecholamide coordinating units, and C₂, C₄, and C₆ spacers) is reported. The formation of complexes with Fe³⁺ was investigated by spectrophotometric (UV-Vis) and spectrometric (ESI, negative ionization mode) methods and corroborated by theoretical (DFT) calculations. Preliminary studies revealed the intricate interplay between the conformational chirality of cyclic trimeric peptoids and metal coordination geometry of mononuclear species similar to that of natural catechol-based siderophores. Experimental results demonstrated the unexpected formation of unique dinuclear Fe³⁺ complexes.

Hexadentate β-Dicarbonyl(bis-catecholamine) Ligands for Efficient Uranyl Cation Decorporation: Thermodynamic and Antioxidant Activity Studies

The special linear dioxo cation structure of the uranyl cation, which relegates ligand coordination to an equatorial plane perpendicular to the O═U═O vector, poses an unusual challenge for the rational design of efficient chelating agents. Therefore, the planar hexadentate ligand rational design employed in this work incorporates two bidentate catecholamine (CAM) chelating moieties and a flexible linker with a β-dicarbonyl chelating moiety (β-dicarbonyl(CAM)₂ ligands). The solution thermodynamics of β-dicarbonyl(CAM)₂ with a uranyl cation was investigated by potentiometric and spectrophotometric titrations. The results demonstrated that the pUO₂²⁺ values are significantly higher than for the previously reported TMA(2Li-1,2-HOPO)₂, and efficient chelation of the uranyl cation was realized by the planar hexadentate β-dicarbonyl(CAM)₂. The efficient chelating ability of β-dicarbonyl(CAM)₂ was attributed to the presence of the more flexible β-dicarbonyl chelating linker and planar hexadentate structure, which favors the geometric arrangement between ligand and uranyl coordinative preference. Meanwhile, β-dicarbonyl(CAM)₂ also exhibits higher antiradical efficiency in comparison to butylated hydroxyanisole. These results indicated that β-dicarbonyl(CAM)₂ has potential application prospects as a chelating agent for efficient chelation of a uranyl cation.

The mono(catecholamine) derivatives as iron chelators: synthesis, solution thermodynamic stability and antioxidant properties research

There is a growing interest in the development of new iron chelators as novel promising therapeutic strategies for neurodegenerative disorders. In this article, a series of mono(catecholamine) derivatives, 2,3-bis(hydroxy)-N-(hydroxyacyl)benzamide, containing a pendant hydroxy, have been synthesized and fully characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy and mass spectrum. The thermodynamic stability of the chelators with Fe^III, Mg^II and Zn^II ions was then investigated. The chelators enable formation of (3 : 1) Fe^III complexes with high thermodynamic stability and exhibited improved selectivity to Fe^III ion. Meanwhile, the results of 1,1-diphenyl-2-picryl-hydrazyl assays of mono(catecholamine) derivatives indicated that they all possess excellent antioxidant properties. These results support the hypothesis that the mono(catecholamine) derivatives be used as high-affinity chelator for iron overload situations without depleting essential metal ions, such as Mg^II and Zn^II ions.