Evaluation of Multidentate Ligands Derived from Ethyl 1,2,4-triazine-3-carboxylate Building Blocks as Potential An(III)-Selective Extractants for Nuclear Reprocessing.

Bis-1,2,4-triazine ligands are amongst the most promising soft N-donor ligands for the partitioning of trivalent actinides from trivalent lanthanides; a key separation proposed in the future reprocessing of spent nuclear fuels. In an effort to improve the extraction properties of these benchmark ligands, we propose herein a general ligand design approach that is inspired by the field of drug discovery, and we apply it to a new class of ligands in which the bidentate 3-(2-pyridyl)-1,2,4-triazine unit of the benchmark ligands is replaced by a bidentate 1,2,4-triazine-3-carboxamide unit. A series of nine novel ligands were synthesized by reactions of readily available ethyl 1,2,4-triazine-3-carboxylate building blocks with different polyamine cores and evaluated for their ability to extract and separate Am(III) and Cm(III) from Eu(III).

A Dual-Purpose Non-Canonical Amino Acid for the Expanded Genetic Code: Combining Metal-Binding and Click Chemistry.

A rationally designed dual-purpose non-canonical amino acid (Trz) has been synthesised and successfully incorporated into a protein scaffold by genetic code expansion. Trz contains a 5-pyridyl-1,2,4-triazine system, which allows for inverse-electron-demand Diels-Alder (IEDDA) reactions to occur on the triazine ring and for metal ions to be chelated both before and after the click reaction. Trz was successfully incorporated into a protein scaffold and the IEDDA utility of Trz demonstrated through the site-specific labelling of the purified protein with a bicyclononyne.

Trinuclear Cyclometalated Iridium(III) Complex Exhibiting Intense Phosphorescence of an Unprecedented Rate.

Herein, we present two novel cyclometalated Ir(III) complexes of dinuclear and trinuclear design, and , respectively, where is 4,6-di(4-tert-butylphenyl)pyrimidine ligand and is acetylacetonate ligand. In both cases, -diastereomers were isolated during the synthesis. The materials show intense phosphorescence of outstanding rates ( = Φ/τ) with corresponding radiative decay times of only τ = 1/ = 0.

Thermally activated delayed fluorescence in a deep red dinuclear iridium(iii) complex: a hidden mechanism for short luminescence lifetimes.

The high luminescence efficiency of cyclometallated iridium(iii) complexes, including those widely used in OLEDs, is typically attributed solely to the formally spin-forbidden phosphorescence process being facilitated by spin-orbit coupling with the Ir(iii) centre. In this work, we provide unequivocal evidence that an additional mechanism can also participate, namely a thermally activated delayed fluorescence (TADF) pathway. TADF is well-established in other materials, including in purely organic compounds, but has never been observed in iridium complexes.

Unusual Excimer/Dimer Behavior of a Highly Soluble C,N Platinum(II) Complex with a Spiro-Fluorene Motif.

In this work, we introduce a spiro-fluorene unit into a phenylpyridine (CN)-type ligand as a simple way to deplanarize the structure and increase the solubility of the final platinum(II)···complex. Using a spiro-fluorene unit, orthogonal to the main coordination plane of the complex, reduces intermolecular interactions, leading to increased solubility but without significantly affecting the ability of the complex to form Pt···Pt dimers and excimers. This approach is highly important in the design of platinum(II) complexes, which often suffer from low solubility due to their mainly planar structure, and offers an alternative to the use of bulky alkyl groups.

Aligning π-Extended π-Deficient Ligands to Afford Submicrosecond Phosphorescence Radiative Decay Time of Mononuclear Ir(III) Complexes.

Herein, we report a profound investigation of the photophysical properties of three mononuclear Ir(III) complexes (Hdppm-4,6-bis(4-(-butyl)phenyl)pyrimidine), (-acetylacetonate), and (Hppy-phenylpyridine). The heteroleptic is found to emit with efficiency above 80% and feature a remarkably high rate of emission. As measured under ambient temperature, emits with the unusually short (sub-μs) radiative decay time of τ = τ/Φ = 1/ = 0.

Exceptionally fast radiative decay of a dinuclear platinum complex through thermally activated delayed fluorescence.

A novel dinuclear platinum(ii) complex featuring a ditopic, bis-tetradentate ligand has been prepared. The ligand offers each metal ion a planar ^^^ coordination environment, with the two metal ions bound to the nitrogen atoms of a bridging pyrimidine unit. The complex is brightly luminescent in the red region of the spectrum with a photoluminescence quantum yield of 83% in deoxygenated methylcyclohexane solution at ambient temperature, and shows a remarkably short excited state lifetime of 2.

Halide-Enhanced Spin-Orbit Coupling and the Phosphorescence Rate in Ir(III) Complexes.

The spin-forbidden nature of phosphorescence in Ir(III) complexes is relaxed by the metal-induced effect of spin-orbit coupling (SOC). A further increase of the phosphorescence rate could potentially be achieved by introducing additional centers capable of further enhancing the SOC effect, such as metal-coordinated halides. Herein, we present a dinuclear Ir(III) complex that contains two Ir(III)-iodide moieties.

Near Infrared Phosphorescent Dinuclear Ir(III) Complex Exhibiting Unusually Slow Intersystem Crossing and Dual Emissive Behavior.

A dinuclear iridium(III) complex shows dual emission consisting of near infrared (NIR) phosphorescence (λ = 714 nm, CHCl, = 300 K) and green fluorescence (λ = 537 nm). The NIR emission stems from a triplet state (T) localized on the ditopic bridging ligand (LC). Because of the dinuclear molecular structure, the phosphorescence efficiency (Φ = 3.

The 5,6,7,8-Tetrahydro-2-Naphthoyl-Coenzyme A Reductase Reaction in the Anaerobic Degradation of Naphthalene and Identification of Downstream Metabolites.

Anaerobic degradation of polycyclic aromatic hydrocarbons has been investigated mostly with naphthalene as a model compound. Naphthalene degradation by sulfate-reducing bacteria proceeds via carboxylation to 2-naphthoic acid, formation of a coenzyme A thioester, and subsequent reduction to 5,6,7,8-tetrahydro-2-naphthoyl-coenzyme A (THNCoA), which is further reduced to hexahydro-2-naphthoyl-CoA (HHNCoA) by tetrahydronaphthoyl-CoA reductase (THNCoA reductase), an enzyme similar to class I benzoyl-CoA reductases. When analyzing THNCoA reductase assays with crude cell extracts and NADH as electron donor via liquid chromatography-mass spectrometry (LC-MS), scanning for putative metabolites, we found that small amounts of the product of an HHNCoA hydratase were formed in the assays, but the downstream conversion by an NAD-dependent β-hydroxyacyl-CoA dehydrogenase was prevented by the excess of NADH in those assays.

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 and Cm from nitric acid.

Conversion of cis-2-carboxycyclohexylacetyl-CoA in the downstream pathway of anaerobic naphthalene degradation.

The cyclohexane derivative cis-2-(carboxymethyl)cyclohexane-1-carboxylic acid [(1R,2R)-/(1S,2S)-2-(carboxymethyl)cyclohexane-1-carboxylic acid] has previously been identified as metabolite in the pathway of anaerobic degradation of naphthalene by sulfate-reducing bacteria. We tested the corresponding CoA esters of isomers and analogues of this compound for conversion in cell free extracts of the anaerobic naphthalene degraders Desulfobacterium strain N47 and Deltaproteobacterium strain NaphS2. Conversion was only observed for the cis-isomer, verifying that this is a true intermediate and not a dead-end product.

Synthesis and Evaluation of Novel 7- and 8-Aminophenoxazinones for the Detection of β-Alanine Aminopeptidase Activity and the Reliable Identification of Pseudomonas aeruginosa in Clinical Samples.

A series of novel 8-aminophenoxazin-3-one and 7-aminophenoxazin-3-one chromogens and their corresponding β-alanine derivatives were synthesized and evaluated for their ability to detect β-alanyl aminopeptidase activity in bacteria known to hydrolyze β-alanine derivatized substrates. The results provided insight into the structural requirements for effective visualization of enzymatic activity and the mechanism of formation of phenoxazinon-3-ones. 8-Aminophenoxazin-3-one substrates 23c, 23d, and 23e were prepared in good to high overall yield and were selective for β-alanyl aminopeptidase activity in bacteria, producing a lighter agar background coloration facilitating visualization of colored colonies, with variable localization to the colonies, but had lower sensitivities for the detection of Pseudomonas aeruginosa in comparison to the analogous 7-aminophenoxazin-3-one substrates.

One-pot synthesis of functionalized piperid-4-ones: a four-component condensation.

The one-pot synthesis of highly substituted piperid-4-ones has been achieved. Diketene is added to a tosyl imine in the presence of TiCl(4) and MeOH, followed by 1 equiv of aldehyde to generate 2,6-disubstituted nonsymmetrical piperid-4-ones as a mixture of cis-/trans-diastereomers in good yields. This mixture of diastereomers can be converted to a single 2,6- cis-diastereomer by epimerization with K(2)CO(3).

Synthesis and testing of chromogenic phenoxazinone substrates for beta-alanyl aminopeptidase.

Novel 7-N-(beta-alanyl)aminophenoxazin-3-one salts 27a-d have been synthesized and tested as chromogenic substrates for beta-alanyl aminopeptidase, which is present in Pseudomonas aeruginosa, the most common respiratory pathogen in patients with cystic fibrosis. The biological results show that 7-N-(beta-alanyl)amino-1-pentylphenoxazin-3-one trifluoroacetate salt 27a is a chromogenic substrate for this bacterium, with a low degree of diffusion in nutrient media for growing bacterial cultures and a bright red colour, making it easily distinguishable from the agar background.