Regioselective Synthesis of V-Shaped Bistriazinyl-phenanthrolines

Novel hydrophilic bistriazolyl-phenanthroline ligands with improved solubility and performance in An/Ln separations

Two novel bistriazolyl-phenanthroline (BTrzPhen) ligands, bearing benzene-sulphonate (DS-BTrzPhen) and amino-acidic (DAA-BTrzPhen) hydrophilizing moieties were developed and found to be more soluble in aqueous acidic media with improved selectivity for Am(iii) over Eu(iii) in solvent extraction studies having SF_Eu/Am values reaching >300. The remarkable activities of both ligands suggest that BTrzPhen ligands are generally still worth exploring and improving.

Synthesis and Evaluation of DHMEQ Derivatives with Tertiary Hydroxyl Group Instead of Secondary Hydroxyl Group

Newly synthesized dehydroxymethyl epoxyquinomycin (DHMEQ) derivatives 6-9, which contain a tertiary hydroxyl group instead of the original secondary hydroxyl group, showed improved solubility in alcohol while maintaining their inhibitory activity against nitric oxide (NO) production, which is used as an indicator of nuclear factor-kappa B (NF-κB) inhibitory activity. We also synthesized a derivative 5 having a cyclopropane ring and a tertiary hydroxyl group and examined its inhibitory activity against NO production. Although it reacted with a nucleophile in a flask, it did not inhibit NO production. The change from a secondary hydroxyl group to a tertiary hydroxyl group contributed to improve the solubility of the compounds while retaining NO inhibitory activity, but had no effect on improving the activity of the cyclopropane form. Compounds in which the secondary hydroxyl group of DHMEQ was converted to a tertiary hydroxyl group would be excellent NF-κB inhibitor candidates because their solubility is improved without decreasing NO inhibitory activity.

Toward Electrochromic Metallopolymers: Synthesis and Properties of Polyazomethines Based on Complexes of Transition-Metal Ions

The tridentate ligand L and its complexes with transition-metal ions have been prepared and characterized. The polycondensation reactions of transition-metal complexes with different dialdehydes led to the formation of transition-metal-complex-based polyazomethines, which have been obtained by on-substrate polymerization, and their electrochemical and electrochromic performance have been investigated. The most interesting properties are exhibited by polymers of Fe(II) and Cu(II) ions obtained by the reaction of the appropriate complexes with a triphenylamine-based dialdehyde. Fe(II) polymer P1 undergoes a reversible oxidation/reduction process and a color change from orange to gray due to the oxidation of Fe(II) to Fe(III) ions concomitant with the oxidation of the triphenylamine group. Its electrochromic properties such as long-term stability, switching times, and coloration efficiencies have been investigated, providing evidence of the utility of the on-substrate polycondensation reaction in the formation of thin films of electrochromic metallopolymers.

Pyridyldiimine macrocyclic ligands: Influences of template ion, linker length and imine substitution on ligand synthesis, structure and redox properties

A series of 2,6-diiminopyridine-derived macrocyclic ligands have been synthesized via [2+2] condensation around alkaline earth metal triflate salts. The inclusion of a tert-butyl group at the 4-position of the pyridine ring of the macrocyclic synthons results in macrocyclic complexes that are soluble in common organic solvents, thereby enabling a systematic comparison of the physical properties of the complexes by NMR spectroscopy, mass spectrometry, solution-phase UV-Vis spectroscopy, cyclic voltammetry and single-crystal X-ray crystallography. Solid-state structures determined crystallographically demonstrate increased twisting in the ligand, concurrent with either a decrease in ion size or an increase in macrocycle ring size (18, 20, or 22 membered rings). The degree of folding and twisting within the macrocycle can be quantified using parameters derived from the N_pyr-M-N_pyr bond angle and the relative orientation of the pyridinediimine (PDI) and pyridinedialdimine (PDAI) fragments to each other within the solid state structures. Cyclic voltammetry and UV-Vis spectroscopy were used to compare the relative energies of the imine π* orbital of the redox active PDI and PDAI components in the macrocycle when coordinated to redox inactive metals. Both methods indicate the change from a methyl to hydrogen substitution on the imine carbon lowers the energy of the ligand π* system.

Exploring the Subtle Effect of Aliphatic Ring Size on Minor Actinide-Extraction Properties and Metal Ion Speciation in Bis-1,2,4-Triazine Ligands

The synthesis and evaluation of three novel bis-1,2,4-triazine ligands containing five-membered aliphatic rings are reported. Compared to the more hydrophobic ligands 1-3 containing six-membered aliphatic rings, the distribution ratios for relevant f-block metal ions were approximately one order of magnitude lower in each case. Ligand 10 showed an efficient, selective and rapid separation of Am^III and Cm^III from nitric acid. The speciation of the ligands with trivalent f-block metal ions was probed using NMR titrations and competition experiments, time-resolved laser fluorescence spectroscopy and X-ray crystallography. While the tetradentate ligands 8 and 10 formed Ln^III complexes of the same stoichiometry as their more hydrophobic analogues 2 and 3, significant differences in speciation were observed between the two classes of ligand, with a lower percentage of the extracted 1:2 complexes being formed for ligands 8 and 10. The structures of the solid state 1:1 and 1:2 complexes formed by 8 and 10 with Y^III , Lu^III and Pr^III are very similar to those formed by 2 and 3 with Ln^III . Ligand 10 forms Cm^III and Eu^III 1:2 complexes that are thermodynamically less stable than those formed by ligand 3, suggesting that less hydrophobic ligands form less stable An^III complexes. Thus, it has been shown for the first time how tuning the cyclic aliphatic part of these ligands leads to subtle changes in their metal ion speciation, complex stability and metal extraction affinity.

Unusual complexation behaviors of R-BTPs with water molecule and Pd(ii) caused by electronic modulation of substituents on BTP backbone: new insights into palladium separation under the framework of minor actinides’ partitioning

A 1 : 1 solid palladium complex with any tridentate bis-triazine ligand has been isolated and structurally characterized for the first time.

Extraction of minor actinides, lanthanides and other fission products by silica-immobilized BTBP/BTPhen ligands

Novel BTBP [bis-(1,2,4-triazin-3-yl)-2,2′-bipyridine]/BTPhen [bis-(1,2,4-triazin-3-yl)-1,10-phenanthroline] functionalized silica gels have been developed to extract minor actinides, lanthanides and other fission products.

Zn-catalyzed hydrohydrazination of propargylamides with BocNHNH2: a novel entry into the 1,2,4-triazine core

Hydrohydrazination of propargylamides with BocNHNH₂ under Zn(OTf)₂ catalysis gave dihydro-1,2,4-triazines which can be efficiently aromatized in situ with K₃[Fe(CN)₆]. This provides a new entry into the medicinally important 1,2,4-triazine core.

Exploring electronic effects on the partitioning of actinides(iii) from lanthanides(iii) using functionalised bis-triazinyl phenanthroline ligands

Revealing how soft N-type donor ligands achieve minor actinide selectivity is fundamental in the design of new and improved extractants for advanced future fuel cycles.