Encapsulation of InP/ZnS Quantum Dots into MOF-5 Matrices for Solid-State Luminescence: Ship in the Bottle and Bottle around the Ship Methodologies.

The utilization of InP-based quantum dots (QDs) as alternative luminescent nanoparticles to cadmium-based QDs is actively pursued. However, leveraging their luminescence for solid-state applications presents challenges due to the sensitivity of InP QDs to oxidation and aggregation-caused quenching. Hence, an appealing strategy is to protect and disperse InP QDs within hybrid materials. Metal-organic frameworks (MOFs) offer a promising solution as readily available crystalline porous materials. Among these, MOF-5 (composed of {Zn4O}6+ nodes and terephthalate struts) can be synthesized under mild conditions (at room temperature and basic pH), making it compatible with InP QDs. In the present work, luminescent InP/ZnS QDs are successfully incorporated within MOF-5 by two distinct methods. In the bottle around the ship (BAS) approach, the MOF was synthesized around the QDs. Alternatively, in the ship in the bottle (SIB) strategy, the QDs were embedded via capillarity into a specially engineered, more porous variant of MOF-5. Comparative analysis of the BAS and SIB approaches, evaluating factors such as operational simplicity, photoluminescence properties, and the resistance of the final materials to leaching were carried out. This comparative study provides insights into the efficacy of these strategies for the integration of InP/ZnS QDs within MOF-5 for potential solid-state applications in materials chemistry.

A triazolium-based fluorophore intercalated in layered double hydroxides: from simple syntheses to bright solid-state luminescence.

This study presents the intercalation into Layered Double Hydroxides (LDHs) of two sulfonated organic molecules featuring the mesoionic triazolium scaffold. These sulfonated fluorophores exhibited excellent solubility in aqueous basic solutions, facilitating their compatibility with the synthesis of LDHs through coprecipitation methods. We applied the size-matching interlayer space (SMIS) approach by substituting a portion of a mono- or dianionic surfactant used in LDH preparation by the sulfonated fluorophore, we aimed to match the size of the luminescent interleaved guest effectively. Our investigation focused on two anion spacers: the classic monoanionic dodecyl sulfate (DS) and the dianionic phenylene dipropionate (PPA). Our results indicated that the latter spacer allowed a more efficient insertion of the fluorescent guest. Thermal resistance analysis underscored the robustness of the final hybrid materials, suggesting a promising design strategy for luminescent materials when applied in diverse applications.

Polymeric copper(I)-NHC complexes with bulky bidentate (N

Starting from imidazolium chlorides bearing bulky nitrogen donors, a series of four complexes, mainly [Cu(C^N)Cl]n coordination polymers were obtained directly as luminescent species by simple filtration from the aqueous reaction medium, highlighting a simple, eco-friendly, robust and reproducible synthetic procedure. Additionally, we have shown on the most efficient example that chloride could be exchanged very easily by other halides/pseudohalides (Br-, I-, NCS-, N3-) allowing to slightly modulate the emitted colour while conserving the polymeric structure, except for azide for which a dimer was obtained. The combination of chemical analyses, of photoluminescence studies in the solid state including quantum yield measurement and X-ray diffraction on single crystals and as-synthesized microcrystalline powders highlighted that the polymeric luminescent species was indeed obtained directly by simple filtration and that no major alteration of the structure was observed upon recrystallisation. Samples of all polymeric complexes displayed remarkable stability towards air oxidation remaining unchanged upon storage for several months and partially retaining their photoluminescence properties even after a thermal treatment at 100 °C for 24 h.

A dicopper(i)-dimesoionic carbene complex as a click catalyst: mechanistic implications.

A dicopper(i) complex comprising a dimesoionic carbene and an acetate-bridge is synthesized and fully characterized. This complex is a potent pre-catalyst for the azide-alkyne cycloaddition reaction. A full kinetic investigation shows a first order in azide and a catalyst order smaller than one due to an equilibrated dimerization of the catalyst.

A catalytic intramolecular nitrene insertion into a copper(i)-N-heterocyclic carbene bond yielding fused nitrogen heterocycles.

N-(2-Azidophenyl)azolium salts were easily prepared and reacted with copper(i) under conditions allowing the formation of NHC complexes. Under these conditions, the formation of benzimidazo-fused heterocycles occurred under catalytic, efficient and very mild conditions. This reaction is proposed to proceed via dinitrogen elimination and imido/nitrene-NHC cyclization.

Cuprophilic interactions in highly luminescent dicopper(i)-NHC-picolyl complexes - fast phosphorescence or TADF?

This case study on a series of monomeric, dimeric and polymeric Cu(I) chlorido NHC-picolyl complexes shows that cuprophilic interactions can ensure strong spin-orbit coupling for fast (reverse)intersystem-crossing T1 ↔ S1 and T1 → S0, and therefore can serve as a design motif for the construction of highly efficient Cu(I)-based TADF or T1 emitters.

Entasis through hook-and-loop fastening in a glycoligand with cumulative weak forces stabilizing Cu(I).

The idea of a possible control of metal ion properties by constraining the coordination sphere geometry was introduced by Vallee and Williams with the concept of entasis, which is frequently postulated to be at stake in metallobiomolecules. However, the interactions controlling the geometry at metal centers remain often elusive. In this study, the coordination properties toward copper ions­Cu(II) or Cu(I)­of a geometrically constrained glycoligand centered on a sugar scaffold were compared with those of an analogous ligand built on an unconstrained alkyl chain. The sugar-centered ligand was shown to be more preorganized for Cu(II) coordination than its open-chain analogue, with an unusual additional stabilization of the Cu(I) redox state. This preference for Cu(I) was suggested to arise from geometric constraints favoring an optimized folding of the glycoligand minimizing steric repulsions. In other words, the Cu(I) d(10) species is stabilized by valence shell electron pair repulsion (VSEPR). This idea was rationalized by a theoretical noncovalent interactions (NCI) analysis. The cumulative effects of weak forces were shown to create an efficient buckle as in a hook-and-loop fastener, and fine structural features within the glycoligand reduce repulsive interactions for the Cu(I) state. This study emphasizes that monosaccharide platforms are appropriate ligand backbones for a delicate geometric control at the metal center, with a network of weak interactions within the ligand. This structuration availing in glycoligands makes them attractive for metallic entasis.

[{Cu(IPr)}2(µ-OH)][BF4]: synthesis and halide-free CuAAC catalysis.

The preparation under protic conditions of the first µ-hydroxo dicopper(I)-NHC complex is reported. Its application as a CuAAC catalyst was investigated, evidencing a remarkable enhancement of catalytic efficiency in the presence of 4,7-dichloro-1,10-phenanthroline and highlighting the beneficial effect of the absence of coordinating halides.

'Auto-click' functionalization for diversified copper(I) and gold(I) NHCs.

Azide-tagged Cu(I)-NHC reacts in an 'auto-click' process to furnish complexes functionalized by 1,2,3-triazoles bearing diverse substituents. The resulting Cu(I) complexes are amenable to further transmetallation to Au(I). The whole strategy proceeds with mild conditions and constitutes an efficient entry to functionalised metal-NHCs with biorelevant moieties.

High-throughput screening of metal-N-heterocyclic carbene complexes against biofilm formation by pathogenic bacteria.

A set of molecules including a majority of metal-N-heterocyclic carbene (NHC) complexes (metal=Ag, Cu, and Au) and azolium salts were evaluated by high-throughput screening of their activity against biofilm formation associated with pathogenic bacteria. The anti-planktonic effects were compared in parallel. Representative biofilm-forming strains of various genera were selected (Listeria, Pseudomonas, Staphylococcus, and Escherichia). All the compounds were tested at 1 mg L(-1) by using the BioFilm Ring Test. An information score (IS, sum of the activities) and an activity score (AS, difference between anti-biofilm and anti-planktonic activity) were determined from normalized experimental values to classify the most active molecules against the panel of bacterial strains. With this method we identified lipophilic Ag(I) and Cu(I) complexes possessing aromatic groups on the NHC ligand as the most efficient at inhibiting biofilm formation.

Luminogenic "clickable" lanthanide complexes for protein labeling.

Development of lanthanide-based luminescent "switch-on" systems via azide-alkyne [3+2] cycloaddition is described. We used these for non-specific protein labeling and as tags for specific and selective activity-based protein labeling.

Access to functionalised silver(I) and gold(I) N-heterocyclic carbenes by [2 + 3] dipolar cycloadditions.

A new strategy was developed for the modification of silver(I) and gold(I) N-heterocyclic carbenes. Azido groups were grafted and used either by copper-catalysed azide-alkyne cycloaddition before metallation or by thermal and "strain-promoted" 1,3-dipolar cycloaddition after metallation to functionalise the metal-NHCs.

Femtomolar Ln(III) affinity in peptide-based ligands containing unnatural chelating amino acids.

The incorporation of unnatural chelating amino acids in short peptide sequences leads to lanthanide-binding peptides with a higher stability than sequences built exclusively from natural residues. In particular, the hexadentate peptide P(22), which incorporates two unnatural amino acids Ada(2) with aminodiacetate chelating arms, showed picomolar affinity for Tb(3+). To design peptides with higher denticity, expected to show higher affinity for Ln(3+), we synthesized the novel unnatural amino acid Ed3a(2) which carries an ethylenediamine triacetate side-chain and affords a pentadentate coordination site. The synthesis of the derivative Fmoc-Ed3a(2)(tBu)(3)-OH, with appropriate protecting groups for direct use in the solid phase peptide synthesis (Fmoc strategy), is described. The two high denticity peptides P(HD2) (Ac-Trp-Ed3a(2)-Pro-Gly-Ada(2)-Gly-NH(2)) and P(HD5) (Ac-Trp-Ada(2)-Pro-Gly-Ed3a(2)-Gly-NH(2)) led to octadentate Tb(3+) complexes with femtomolar stability in water. The position of the high denticity amino acid Ed3a(2) in the hexapeptide sequence appears to be critical for the control of the metal complex speciation. Whereas P(HD5) promotes the formation of polymetallic species in excess of Ln(3+), P(HD2) forms exclusively the mononuclear complex. The octadentate coordination of Tb(3+) by both P(HD) leads to total dehydration of the metal ion in the mononuclear complexes with long luminescence lifetimes (>2 ms). Hence, we demonstrated that unnatural amino acids carrying polyaminocarboxylate side-chains are interesting building blocks to design high affinity Ln-binding peptides. In particular the novel peptide P(HD2) forms a unique octadentate Tb(3+) complex with femtomolar stability in water and an improvement of the luminescence properties with respect to the trisaquo TbP(22) complex by a factor of 4.

A water soluble Cu(I)-NHC for CuAAC ligation of unprotected peptides under open air conditions.

A reducing agent-free version of CuAAC able to operate under open air conditions is reported. A readily-synthesizable, hydrophilic and highly stable Cu(I)-NHC allows the clean ligations of unprotected peptides comprising sensitive side chains, at millimolar concentrations.

Use of copper(I) catalyzed azide alkyne cycloaddition (CuAAC) for the preparation of conjugated pyrrolo[2,3-a]carbazole Pim kinase inhibitors.

We have previously demonstrated that pyrrolo[2,3-a]carbazole-3-carbaldehydes are potent Pim kinase inhibitors with in vitro antiproliferative activities. In the present study, we report the synthesis of new pyrrolocarbazoles substituted at the N-10 position. When their ability to inhibit Pim kinase activities were evaluated in in vitro assays, we observed that this nitrogen atom can be substituted without loss of Pim-1 and Pim-3 inhibitory potencies. Moreover, when we added a fluorescent dansyl group (compound 13), we were able to show that 13 penetrates the plasma membrane and enters the cytoplasm.

Lanthanide-binding peptides with two pendant aminodiacetate arms: impact of the sequence on chelation.

Lanthanide complexes with a series of hexapeptides-incorporating two unnatural chelating amino acids with aminodiacetate groups, Ada(1) and Ada(2)-have been examined in terms of their speciation, structure, stability and luminescence properties. Whereas Ada(2) acts as a tridentate donor in all cases, Ada(1) may act as a tetradentate donor thanks to the coordination of the amide carbonyl function assisted by the formation of a six-membered chelate ring. The position of the Ada(1) residue in the sequence is demonstrated to be critical for the lanthanide complex speciation and structure. Ada(1) promotes the coordination of the backbone amide function to afford a highly dehydrated Ln complex and an S-shape structure of the peptide backbone, only when found in position 2.

Advances in metal-carbene complexes as potent anti-cancer agents.

This critical review is an updated survey of metal-carbenes as potential anticancer chemotherapeutics. We report on the recent advances in the discovery of N-heterocyclic carbenes, acyclic diamino carbenes and abnormal NHCs associated with metals from groups 10 and 11 that displayed antiproliferative activity and emphasize, when possible, their molecular target(s) and their mechanism of action.

A platinum Chugaev carbene complex as a potent anticancer agent.

A platinum Chugaev complex was synthesised and fully characterized by multinuclear NMR spectroscopy and X-ray crystallography. This cis bis acyclic diamino carbene complex acts as a cytotoxic compound and behaves as a cisplatin equivalent by interacting with supercoiled DNA and thiols. Stability of the ligand is also discussed.

A lanthanide binding peptide with short chelating side-chains: structural impact of the backbone coordination.

A lanthanide-binding hexapeptide containing two short aminodiacetate side-chains favours the coordination of a backbone carbonyl, which determines the secondary structure of the complex and illustrates the interplay between complex formation and secondary peptide structures.