A New Photoresponsive Bis (Crown Ether) for Extraction of Metal Ions

Polydentate N,O-Ligands Possessing Unsymmetrical Urea Fragments Attached to a p-Cresol Scaffold

In this study, three series of polydentate N,O-ligands possessing unsymmetrical urea fragments attached to a p-cresol scaffold are obtained, namely mono- and bi-substituted open-chain aromatics, synthesised using a common experiment, as well as fused aryloxazinones. Separate protocols for the preparation of each series are developed. It is found that in the case of open-chain compounds, the reaction output is strongly dependent on both bis-amine and carbamoyl chloride substituents, while oxazinones can be effectively obtained via a common protocol. The products are characterized via 1D and 2D NMR spectra in solution and using single-crystal XRD. A preliminary study on the coordination abilities of the products performed via ITC shows that there are no substantial interactions in the pH range of 5.0-8.5 in general.

Cyclometallated Platinum(II) Complexes with Small Crown Ether Rings: Appropriate Choice of the Bridging Diphosphane to Coordinate Potassium Cations

This account reports the synthesis and structural characterization of the first cyclometallated platinum(II) complex that coordinates a potassium cation in a sandwich arrangement via two 15-crown-5 ether rings within the same molecule. The cooperation of the two small crown ether moieties allows the entrapment of the non-ideal potassium ion. The reaction of the parent thiosemicarbazone ligand 3,4-(C₈H₁₆O₅)C₆H₃C(Me)=NN-(H)C(=S)NHMe, 1, containing the crown ether ring, with K₂[PtCl₄], or alternatively with PtCl₂(DMSO)₂, and subsequent treatment with the diphosphanes Ph₂PCH₂PPh₂ (dppm) and Ph₂PC(=CH₂)PPh₂ (vdpp) produced the double nuclear platinacycles 3a, 3b, and 4, probably via formation of the 2a and 2b intermediates. Complex 3a with the K⁺ cation in a sandwich coordination was slightly mixed with 3b lacking any K⁺. Alternatively, reaction of 1 with K₂[PtCl₄] or with PtCl₂(DMSO)₂ followed by the diphosphane Ph₂PC(=CH₂)PPh₂ (vdpp) only gave the dinuclear phosphane-bridged compound 4; this highlights the importance of choosing the right diphosphane ligand. Density functional theory calculations (B3LYP-D3/LANL2DZ-ECP-6.311++G**) revealed similar affinities for both dppm and vdpp derivatives to coordinate potassium cations. Crystal structure analysis was performed for compounds 3a and 4.

Chelating Extractants for Metals

In the present review, works on the classes of chelating extractants for metals, compounds with several amide and carboxyl groups, azomethines, oximes, macrocyclic compounds (crown ethers and calixarenes), phenanthroline derivatives, and others are systematized. This review focuses on the efficiency and selectivity of the extractants in the recovery of metals from industrial wastewater, soil, spent raw materials, and the separation of metal mixtures. As a result of this study, it was found that over the past seven years, the largest number of works has been devoted to the extraction of heavy metals with amino acids (16 articles), azomethines and oximes (12 articles), lanthanids with amide compounds (15 articles), lanthanides and actinides with phenanthroline derivatives (7 articles), and noble metals with calixarenes (4 articles). Analysis of the literature showed that amino acids are especially effective for extracting heavy metals from the soil; thiodiglycolamides and aminocalixarenes for extracting noble metals from industrial waste; amide compounds, azomethines, oximes, and phenanthroline derivatives for extracting actinides; amide compounds for extracting lanthanides; crown ethers for extracting radioactive strontium, rhenium and technetium. The most studied parameters of extraction processes in the reviewed articles were the distribution ratios and separation factors. Based on the reviewed articles, it follows that chelate polydentate compounds are more efficient compounds for the extraction of metals from secondary resources compared to monodentate compounds.

Acylpyrazolones possessing a heterocyclic moiety in the acyl fragment: intramolecular vs. intermolecular zwitterionic structures

A series of acylpyrazolones possessing a methylene bridged heterocyclic unit in the acyl fragment are synthesized and characterized in solution and the solid state.