Selective CO₂ capture in metal-organic frameworks with azine-functionalized pores generated by mechanosynthesis

Two new three-dimensional porous Zn(II)-based metal-organic frameworks, containing azine-functionalized pores, have been readily and quickly isolated via mechanosynthesis, by using a nonlinear dicarboxylate and linear N-donor ligands. The use of nonfunctionalized and methyl-functionalized N-donor ligands has led to the formation of frameworks with different topologies and metal-ligand connectivities and therefore different pore sizes and accessible volumes. Despite this, both metal-organic frameworks (MOFs) possess comparable BET surface areas and CO₂ uptakes at 273 and 298 K at 1 bar. The network with narrow and interconnected pores in three dimensions shows greater affinity for CO compared to the network with one-dimensional and relatively large pores-attributable to the more effective interactions with the azine groups

A hybrid bis(amino-styryl) substituted Bodipy dye and its conjugate diacid: synthesis, structure, spectroscopy and quantum chemical calculations

International audienceA new type of fluorescent pH indicator has been developed whereby two dissimilar amino-styryl units are attached to a boron dipyrromethene (Bodipy) dye. The photophysical properties of this hybrid dye, and its simpler counterparts bearing only a single amino-styryl residue, depend on the polarity of the surrounding medium. Of the two terminal amines, DFT (B3LYP/6-31G**) calculations and spectroscopic measurements support the notion that julolidine is oxidised and protonated under milder conditions than is N,N-dimethylaniline. For the hybrid dye, similar DFT calculations carried out for the mono-protonated analogues indicate that the julolidine residue is the stronger base while the resultant conjugate acid is the weaker one. Absorption and fluorescence spectroscopic titrations show that protonation of the hybrid dye occurs in two well-resolved steps, whereby addition of the first proton introduces a thermodynamic barrier for entry of the second. In the hybrid dye, the pKA values for the respective conjugate acids differ markedly from those derived for the mono-amino-styryl dyes and display negative co-operativity. Effectively, this means that electronic interactions running along the molecular backbone make it more difficult, relative to the individual dyes, to protonate both amino sites. As such, this dye operates as a probe over an unusually wide pH range

Synthesis of Indolo[3,2-b]carbazole based boron complexes with tunable photophysical and electrochemical properties

New synthetic strategies were developed for the synthesis of indolo-pyridine boron difluoride (IPBD) dyes and antiladder-type π-conjugated dyes based on the pyridine/pyrazine-indolocarbazole (ICZ) structures. The photophysical and electrochemical properties of the dyes were measured in solution, solid state, and thin films and rationalized by theoretical calculations. Interestingly, these properties of the dyes can be tuned in a wide range using the developed chemical route. For example, the absorption range and fluorescence color of the dyes in solution and solid state and the HOMO–LUMO energy gaps were tuned by structure modulations. The absorption properties of those new boron complexes cover most of the UV–visible-NIR spectrum. Therefore, this appealing tunability feature makes these new types of dyes very promising candidates for their further use in functional material development

An histidine covalent receptor and butenolide complex mediates strigolactone perception

Strigolactone plant hormones control plant architecture and are key players in both symbiotic and parasitic interactions. They contain an ABC tricyclic lactone connected to a butenolide group, the D ring. The DWARF14 (D14) strigolactone receptor belongs to the superfamily of α/β-hydrolases, and is known to hydrolyze the bond between the ABC lactone and the D ring. Here we characterized the binding and catalytic functions of RAMOSUS3 (RMS3), the pea (Pisum sativum) ortholog of rice (Oryza sativa) D14 strigolactone receptor. Using new profluorescent probes with strigolactone-like bioactivity, we found that RMS3 acts as a single-turnover enzyme that explains its apparent low enzymatic rate. We demonstrated the formation of a covalent RMS3-D-ring complex, essential for bioactivity, in which the D ring was attached to histidine 247 of the catalytic triad. These results reveal an undescribed mechanism of plant hormone reception in which the receptor performs an irreversible enzymatic reaction to generate its own ligand

Structural, stability and relaxation features of lanthanide‐complexes designed for multimodal imaging detection of enzyme activities

International audienceLanthanide complexes of DO3A‐derivative ligands bearing a pyridine‐carbamate ( L1 ) or pyridine‐amine ( L2 ) arm have potential interest in the design of enzymatically activated imaging probes. Solid‐state X‐ray structures for CeL1 and YbL2 both demonstrate twisted square antiprismatic geometry, with the metal ion in a nine‐ or an eight‐coordinate environment, respectively. As assessed by pH‐potentiometry, in solution lanthanide ions form more stable complexes with the nonadentate L1 than with the octadentate L2 ligand (log K ML =18.7–21.1 vs. 16.7–18.6, respectively), while stability constants are similar for L1 and L2 chelates of Mg 2+ , Ca 2+ , Zn 2+ or Cu 2+ . The kinetic inertness of GdL1 is exceptionally high, with an estimated dissociation half‐life of ~10 8 h at pH 7.4, while LnL2 (Ln=Ce, Gd, Yb) complexes have 3–4 orders of magnitude faster dissociation, related to the presence of the protonatable, non‐coordinating amine function. The water exchange rate determined for the monohydrated GdL2 ( k ex 298 =1.3×10 6 s −1 ) shows a threefold decrease with respect to GdDOTA, as a consequence of a reduction in the negative charge and in the steric crowding around the water binding site, both important in dissociatively activated water exchange processes

Synthesis, cytotoxicity, antibacterial and antileishmanial activities of imidazolidine and hexahydropyrimidine derivatives.

International audienceThis paper describes the synthesis and in vitro biological activities of imidazolidine and hexahydropyrimidine derivatives against bacteria (Escherichia coli, Staphylococcus aureus and Mycobacterium tuberculosis) and Leishmania protozoa. Out of sixteen heterocyclic derivatives tested, none were cytotoxic against mammalian cells. The compounds showed significant bacterial effects and leishmanicidal activity. Compounds 4a and 4c were active against S. aureus and E. coli, respectively. Compounds 3a-3f, 4h and 4i presented promising results against M. tuberculosis, with MIC values ranging from 12.5 to 25.0 μg/mL, comparable to the "first and second line" drugs used to treat tuberculosis. Compounds 4a, 4c and 4e were active against L major. Three of them were structurally characterized by single-crystal X-ray diffraction

Synthesis and evaluation of original bioisosteres of bacterial type IIA topoisomerases inhibitors

International audienceA recently discovered series of inhibitors of the ATPase function of bacterial type IIA topoisomerases featuring a carboxypyrrole component led us to attempt to replace this group with a potentially bioisosteric carboxypyrazole. Accordingly, synthetic pathways to 2-(4-(1H-pyrazole-5-carboxamido)piperidin-1-yl)thiazole-5-carboxylic acids or 2-(4-(N-methyl-1H-pyrazole- 5-carboxamido)piperidin-1-yl)thiazole-5-carboxylic acids featuring an array of substituents on the pyrazole ring were explored. Unfortunately, none of the analogues made were effective on the ATPase function of Mycobacterium tuberculosis gyrase as well on the DNA supercoiling activity of the whole gyrase of M. tuberculosis and Escherichia coli. However, this work is still providing original insights in chemistry as well as in the structure–activity relationships of this series of inhibitorsUne série récente d’inhibiteurs de la fonction ATP-asique des topoisomérases bactériennes de type IIA comportant un noyau carboxypyrrole nous a conduits à tenter de remplacer celui-ci par un noyau carboxypyrazole bioisostère. Ainsi, des accès aux dérivés d’acide 2-(4-(1H-pyrazole-5-carboxamido)piperidin-1-yl)thiazole-5-carboxylique, comportant une gamme de substituants, ont été explorés. Malheureusement, aucun des analogues préparés n’a eu d’effet, que ce soit sur la fonction ATP-asique de la gyrase de Mycobacterium tuberculosis ou sur l’activité de surenroulement des gyrases de M. tuberculosis ou d’Escherichia coli. Toutefois, ce travail représente une contribution originale en ce qui concerne la chimie ou les relations structure–activité de cette série d’inhibiteurs