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The theoretical basis of neuronal coding, associated with short-term degradation in synaptic transmission, is a matter of debate in the literature. In fact, electrophysiological signals are commonly characterized as inversely proportional to stimulus intensity. Among theoretical descriptions of this phenomenon, models based on 1/f -dependency are employed to investigate the biophysical properties of short-term synaptic depression. In this work, we formulate a model based on a paradigmatic q-differential equation to obtain a generalized formalism useful for investigation of nonextensivity in this specific type of synaptic plasticity. Our analysis reveals nonextensivity in data from electrophysiological recordings and also a statistical crossover in neurotransmission. In particular, statistical transitions provide additional support to the hypothesis of heterogeneous release probability of neurotransmitters. On the other hand, the simple vesicle model agrees with data only at low-frequency stimulations. Thus, the present work presents a method to demonstrate that short-term depression is not only governed by random mechanisms but also by nonextensive behavior. Our findings also conciliate morphological and electrophysiological investigations into a coherent biophysical scenario. [ABSTRACT FROM AUTHOR]

[M(NH3)5Cl][IrCl6], M = Co, Cr, Ru, Rh, and Ir, were proposed as single-source precursors for bimetallic alloys. Their thermal decomposition in inert and reductive atmospheres below 700 °C results in the formation of nanostructured porous Ir0.5M0.5 alloys. Salts decompose with a significant exothermal effect during the first stage of their thermal breakdown in an inert atmosphere above 200 °C. The exothermal effect gradually decreases in the series: [Co(NH3)5Cl][IrCl6] (1) ＞ [Cr(NH3)5Cl][IrCl6] (2) ＞ [Ru(NH3)5Cl][IrCl6] (3) ＞ [Rh(NH3)5Cl][IrCl6] (4); [Ir(NH3)5Cl][IrCl6] (5) does not exhibit any thermal effects and decomposes at much higher temperatures. To shed light on their thermal decomposition and the nature of the exothermal effect, DSC–EGA, in situ and ex situ IR, Raman, XPS and XAFS studies were performed. A combination of complementary techniques suggests a simultaneous ligand exchange and a reduction of central atoms as key processes. In [Co(NH3)5Cl][IrCl6], Co(iii) and Ir(iv) simultaneously oxidise coordinated ammonia, which can be detected due to a significant exothermal effect and the presence of Co(ii) and Ir(iii) in the intermediate product. The appearance of Ir–N frequencies demonstrates a ligand exchange between cations and the [IrCl6]2− anion. Salts with Cr(iii), Ru(iii), and Rh(iii) show a much lower exothermal effect due to the stability of their oxidation states. Salts with Rh(iii) and Ir(iii) demonstrate a high thermal stability and a low tendency for ligand exchange as well as decomposition with exothermal effects. [ABSTRACT FROM AUTHOR]

New hybrid POM based on Lindqvist-type polyoxometalates [M6O19]8− (M = Nb, Ta) and organometallic fragment {Cp*Rh}2+ have been isolated and characterized. X-ray quality crystals of K4[(Cp*Rh)2Nb6O19]·20H2O (1) and Cs4[(Cp*Rh)2Ta6O19]·18H2O (2) were obtained from solutions with {Cp*Rh} : [M6O19]8− stoichiometry 2 : 1. The solution behavior of the hybrid polyoxoanions was studied with ESI-MS and 1H DOSY NMR. Amongst the poorly investigated chemistry of polyoxotantalates, complex 2 is the first complex bearing a grafted organometallic fragment. The formation of 1 : 1 complexes was detected by ESI-MS techniques. [ABSTRACT FROM AUTHOR]

Reaction of [(C6H6)RuCl2]2 and Na8[Ta6O19] gives two new hybrid organometallic POM complexes, Na10[{(C6H6)RuTa6O18}2(µ-O)]·39.4H2O (Na10-1) and Na4(trans-[{(C6H6)Ru}2Ta6O19]·20H2O (Na4-2). In both cases the half-sandwich fragments {(C6H6)Ru}2+ are coordinated as additional vertices to the {Ta3(µ2-O)3} triangles of the hexatantalate. According to NMR and ESI-MS data, the dimeric complex [{(C6H6)RuTa6O18}2(µ-O)]10- dissociates in water with the formation of monomeric [(C6H6)RuTa6O19]6- species (1a). X-ray structural characterization and aqueous speciation of the complexes by 13C, ¹H, and DOSY NMR; ESI-MS; and capillary electrophoresis (CE) have been carried out. [ABSTRACT FROM AUTHOR]

Inhibition of the biosynthesis of bacterial heptoses opens novel perspectives for antimicrobial therapies. The enzyme GmhA responsible for the first committed biosynthetic step catalyzes the conversion of sedoheptulose 7-phosphate into d- glycero -d- manno -heptose 7-phosphate and harbors a Zn 2+ ion in the active site. A series of phosphoryl- and phosphonyl-substituted derivatives featuring a hydroxamate moiety were designed and prepared from suitably protected ribose or hexose derivatives. High-resolution crystal structures of GmhA complexed to two N -formyl hydroxamate inhibitors confirmed the binding interactions to a central Zn 2+ ion coordination site. Some of these compounds were found to be nanomolar inhibitors of GmhA. While devoid of HepG2 cytotoxicity and antibacterial activity of their own, they demonstrated in vitro lipopolysaccharide heptosylation inhibition in Enterobacteriaceae as well as the potentiation of erythromycin and rifampicin in a wild-type Escherichia coli strain. These inhibitors pave the way for a novel treatment of Gram-negative infections.

Natural cyclodextrin (CD) macrocycles are known to form diverse inclusion complexes with a wide variety of organic molecules, but recent work has revealed that inorganic clusters also form multicomponent supramolecular complexes and edifices. Such molecular assemblies exhibit a high degree of organization in solution governed by various chemical processes including molecular recognition, host-guest attraction, hydrophobic repulsion, or chaotropic effect. Nuclear magnetic resonance (NMR) spectroscopy is one of the most efficient and practical analytical techniques to characterize the nature, the strength and the mechanism of these interactions in solution. This review provides a brief overview on recent examples of the contribution of NMR to the characterization of hybrid systems in solution based on CD with polynuclear clusters, including polyoxometalates (POMs), metallic clusters and hydroborate clusters. The focus will be first on using 1 H (and 13 C) NMR of the host, i.e. , CD, to identify the nature of the interactions and measure their strength. Then, 2D NMR methods will be illustrated by DOSY as a means of highlighting the clustering phenomena, and by NOESY/ROESY to evidence the spatial proximity and contact within the supramolecular assemblies. Finally, other NMR nuclei will be selected to probe the inorganic part as a guest molecule. Attention will be paid to classical host-guest complexes Cluster@CD, but also to hierarchical multi-scale, multi-component assemblies such as Cluster@CD@Cluster.

This paper deals with the synthesis, characterization, and studies of biological properties of a series of 5 coordination compounds based on binuclear core [Mo (V) 2 S 2 S 2 ] 2+ with thiosemicarbazones ligands bearing different substituents on the R 1 position of the ligand. The complexes are first studied using MALDI-TOF mass spectrometry and NMR spectroscopy to determine their structures in solution in relation to single-crystal X-Ray diffraction data. In a second part, the antifungal and antioxidative activities are explored and the high potential of these coordination compounds compared to the uncoordinated ligands is demonstrated for these properties. Finally, DFT calculation provides important support to the solution studies by identifying the most stable isomers in each [Mo 2 S 2 S 2 ] 2+ /Ligand system, while the determination of HUMO and LUMO levels is performed to explain the antioxidative properties of these systems., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

A selective access to perfluoroalkyl selenoxides, via Oxone® as oxidant or to selenones by using a Polyoxometalate-based Ionic Liquid (POM-IL) as a catalyst for the oxidation step is described. The reaction works with various perfluoralkyl chains and substituents with satisfactory to excellent yields. A two-step one-pot reaction from selenocyanates was performed to gain access to perfluoroalkyl selenoxides. The previously unknown perfluoroalkyl selenoximines family was also prepared with good yields. Having unlocked two strategies for the synthesis of fluoroalkylated Se IV and Se VI compounds, we then evaluated the Hansch-Leo lipophilicity parameters of these groups. Finally, asymmetric aryl perfluoroalkyl selenoximines were resolved to determine their absolute configurations., (© 2023 Wiley-VCH GmbH.)

[MoV2O 2 S 2 ] 2+ -based thiosemicarbazone complexes appear as very promising molecules for biological applications due to the intrinsic properties of their components. This paper deals with the synthesis and characterization of six coordination complexes obtained by the reaction of [MoV2O 2 S 2 ] 2+ clusters with bis-thiosemicarbazone ligands that contain flexible or rigid spacers between the two thiosemicarbazone units. Interestingly, structural characterization by single-crystal X-ray diffraction, MALDI-TOF MS technique and NMR spectroscopy revealed that the nuclearity of the complex is controlled by the nature of the spacer between the thiosemicarbazone units. Binuclear complexes, namely [MoV2O 2 S 2 (L 1-3 )], are isolated with flexible spacers while tetranuclear complexes [(MoV2O 2 S 2 ) 2 (L 4-6 ) 2 ] are formed when the bis-thiosemicarbazone ligands are built on rigid spacers.

Herein we report the synthesis of a new class of compounds associating Keggin and Dawson-type Polyoxometalates (POMs) with a derivative of the anionic decahydro- closo -decaborate cluster [B 10 H 10 ] 2- through aminopropylsilyl ligand (APTES) acting as both a linker and a spacer between the two negatively charged species. Three new adducts were isolated and fully characterized by various NMR techniques and MALDI-TOF mass spectrometry, notably revealing the isolation of an unprecedented monofunctionalized SiW 10 derivative stabilized through intramolecular H-H dihydrogen contacts. DFT as well as electrochemical studies allowed studying the electronic effect of grafting the decaborate cluster on the POM moiety and its consequences on the hydrogen evolution reaction (HER) properties.

This paper deals with the synthesis, structural studies, and behavior in solution of unprecedented coordination complexes built by the association of a panel of 14 representative thiosemicarbazone ligands with the cluster [Mo 2 O 2 S 2 ] 2+ . These complexes have been thoroughly characterized both in the solid state and in solution by XRD and by NMR, respectively. In particular, HMBC 1 H{ 15 N} and 1 H DOSY NMR experiments bring important elements for understanding the complexes' behavior in solution. These studies demonstrate that playing on the nature and the position of various substituents on the ligands strongly influences the coordination modes of the ligands as well as the numbers of isomers in solution, mainly 2 products for the majority of complexes and up to 5 for some of them., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

This paper deals with the biological potential of coordination compounds based on binuclear core [Mo V 2 O 2 E 2 (E = O or S) coordinated with commercially available ligands such as oxalates (Ox 2+ (E = O or S) coordinated with commercially available ligands such as oxalates (Ox 2- ), L-cysteine (L-cys 2- ), L-histidine (L-his - ), Iminodiacetate (IDA 2- ), Nitrilotriacetate (HNTA 2- or NTA 3- ) or ethylenediamine tetraacetate (EDTA 4- ) by means of various in vitro assays in a screening approach. Results suggest that the obtained complexes show weak antibacterial and antifungal properties while not being cytotoxic on cancerous and mammalian cells. In contrast, [Mo 2 O 2 E 2 (L-cys) 2 ] 2- complexes stand out as powerful antioxidant, whereas [Mo 2 O 2 E 2 (EDTA)] 2- associating tetraphenylphosphonium counter-cations display strong antibiotic activity. Finally, some complexes have evidenced a positive activity towards the growing of spirulina platensis together with a modification of the proportions of biological components inside the cells. These findings reveal promising bioactivity of the bridged binuclear Mo (+V) cores inside complexes and encourage further research for new highly active yet non-toxic molecules for biological and biomedical applications., (Copyright © 2021. Published by Elsevier Inc.)

This paper deals with the preparation and the characterization of four new ionic liquids resulting from the pairing of various polyoxotungstates or polyoxomolybdates with the cation trihexyltetradecylphosphonium. The physical properties measured by different techniques evidence that the viscosity and the rheological behaviors of such POM-based ionic liquids, POM-ILs, strongly depend on the nature of the POM, especially its charge. Playing on the nature of the POM, we can indeed obtain Newtonian liquids or some much more viscous materials exhibiting characteristics of resins or pseudo-plastics. In a second part of this study, the potentialities of using such materials both as solvent and catalyst for the oxidation of a series of alcohols are presented as proof of concept. This part highlights great differences in strength and selectivity as a function of the POM-IL used. Furthermore, a very simple way to recycle the catalyst is also presented.

A novel decahydrodecaborate-functionalized Anderson type polyoxometalate has been synthesized and characterized in solution by ESI-MS, various NMR techniques and electrochemical methods. DFT studies provide strong support to understand the properties of this hybrid system.

Water-soluble salts of anionic [Re 6 Q 8 (CN) 6 ] 4- (Q=S, Se, Te) chalcogenide octahedral rhenium clusters react with γ-cyclodextrin (γ-CD) producing a new type of inclusion compounds. Crystal structures determined through single-crystal X-ray diffraction analysis revealed supramolecular host-guest assemblies resulting from close encapsulations of the octahedral cluster within two γ-CDs. Interestingly, nature of the inner Q ligands influences strongly the host-guest conformation. The cluster [Re 6 S 8 (CN) 6 ] 4- interacts preferentially with the primary faces of the γ-CD while the bulkier clusters [Re 6 Se 8 (CN) 6 ] 4- and [Re 6 Te 8 (CN) 6 ] 4- exhibit specific interactions with the secondary faces of the cyclic host. Furthermore, analysis of the crystal packing reveals additional supramolecular interactions that lead to 2D infinite arrangements with [Re 6 S 8 (CN) 6 ] 4- or to 1D "bamboo-like" columns with [Re 6 Se 8 (CN) 6 ] 4- and [Re 6 Te 8 (CN) 6 ] 4- species. Solution studies, using multinuclear NMR methods, ESI-MS and Isothermal titration calorimetry (ITC) corroborates nicely the solid-state investigations showing that supramolecular pre-organization is retained in aqueous solution even in diluted conditions. Furthermore, ITC analysis showed that host-guest stability increases significantly ongoing from S to Te. At last, we report herein that deep inclusion alters significantly the intrinsic physical-chemical properties of the octahedral clusters, allowing redox tuning and near IR luminescence enhancement., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Formation of one of the most representative polyoxometalate (POM) archetypes, namely the Lindqvist anion M 6 O 19 2- with M = Mo VI or W VI , was considered as elusive in aqueous solution. Herein, we report on the host-guest stabilization of the M 6 O 19 2- species with M = Mo or W from aqueous solution using γ-cyclodextrin as trapping agent. The adduct {M 6 O 19 @γ-CD} 2- reveals remarkable hydrolytic stability that offers new opportunities for exploring potentialities of molybdates or tungstates in the field of biology and medicine, when combined to CDs as efficient drug carrier/delivery agents.

Self-assembly reactions of Na 2 WO 4 , SeO 2 /SeO 3 2- , and [Mo 2 (μ-S) 2 (μ-S) 2 (H 2 O) 6 ] 2+ give, depending on the pH value, two new large polyoxometalate complexes: i.e., [(γ-Se 2 W 14 O 52 ) 3 (Mo 2 (μ-S) 2 (μ-S) 2 (H 2 O) 2 ) 6 ] 24- (1) isolated at pH 3.5 and [(γ-Se 2 W 14 O 52 ) 4 (WO 3 (H 2 O)) 8 (W 2 O 5 ) 2 (W 4 O 12 ) 2 (Mo 2 (μ-S) 2 (μ-S) 2 (H 2 O) 2 ) 4 (Mo 2 (μ-S) 2 (μ-S) 2 (SeO 3 )) 4 ] 36- (2) isolated at pH 2. Both compounds were characterized in the solid state by single-crystal X-ray diffraction, EDX, elemental analysis, TGA, and FT-IR and in solution by ESI-MS and NMR.

In this communication, we report on a noteworthy hybrid supramolecular assembly built from three functional components hierarchically organized through noncovalent interactions. The one-pot synthesis procedure leads to the formation of large Mo-blue ring-shaped anion {Mo 154 }, which contains the supramolecular adduct based on the symmetric encapsulation of the Dawson-type [P 2 W 18 O 62 ] 6- anion by two γ-cyclodextrin units. Such a nanoscopic onion-like structure, noted [P 2 W 18 O 62 ]@2γ-CD@{Mo 154 } has been characterized by single-crystal X-ray diffraction, thus demonstrating the capability of the giant inorganic torus to develop relevant supramolecular chemistry, probing the strong affinity of the inner and outer faces of the γ-CD for the polyoxometalate surfaces. Furthermore, interactions and behavior in solution have been studied by multinuclear NMR spectroscopy, which supports specific interactions between γ-CD and POM units. Finally, the formation of this three-component hybrid assembly from one-pot procedure, in water and using nearly stoichiometric conditions, is discussed in terms of the driving forces orchestrating this highly efficient multilevel recognition process.

Herein, we report on a three-component supramolecular hybrid system built from specific recognition processes involving a Dawson-type polyoxometalate (POM), [P 2 W 18 O 62 ] 6- , a cationic electron-rich cluster [Ta 6 Br 12 (H 2 O) 6 ] 2+ , and γ-cyclodextrin (γ-CD). Such materials have been investigated using a bottom-up approach by studying the specific interactions between γ-CD and both types of inorganic units. Their ability to interact has been investigated in the solid state by single-crystal X-ray diffraction (XRD) and in solution using multinuclear NMR methods (including DOSY, EXSY, and COSY), electrospray ionization mass and UV-vis spectroscopies, electrochemistry, and isothermal titration calorimetry experiments. Single-crystal XRD analysis reveals that POM:γ-CD constitutes a highly versatile system which gives aggregates with 1:1, 1:2, and 1:3 stoichiometry. Surprisingly, these arrangements exhibit a common feature wherein the γ-CD moiety interacts with the Dawson-type POMs through its primary face. We present also the first structural model involving an octahedral-type metallic cluster with γ-CD. XRD study reveals that the cationic [Ta 6 Br 12 (H 2 O) 6 ] 2+ ion is closely embedded within two γ-CD units to give a supramolecular ditopic cation, suitable to be used as a linker within extended structure. Solution study demonstrates clearly that pre-associations exist in solution, for which binding constants and thermodynamic parameters have been determined, giving preliminary arguments about the chaotropic nature of the inorganic ions. Finally, both building blocks, i.e., the ditopic supramolecular cation {[Ta 6 Br 12 (H 2 O) 6 ]@2CD} 2+ and the Dawson-type anion, react together to give a three-component, well-ordered hybrid material derived either as a supramolecular hydrogel or single crystals. The solid-state structure shows an unprecedented helicoidal tubular chain resulting from the periodic alternation of POM and supramolecular cation, featuring short hydrogen-bonding contacts between the electron-poor POM and electron-rich cluster. The 1D tubular ionic polymer observed in the single crystals should make it possible to understand the long-range ordering observed within the hydrogel hybrid material. The supramolecular chemical complementarities between the γ-CD-based ditopic cation and POM open a wide scope for the design of hybrid materials that accumulate synergistic functionalities.

The host-guest interactions between the spherical porous Keplerate anion, [Mo132O372(CH3CO2)30(H2O)72](42-) (abbreviated {Mo132}) and the tetramethylammonium cation have been investigated extensively by one- and two-dimensional (EXSY, ROESY, and DOSY) and variable-temperature NMR. Evidence of two inner receptor sites specific for a NMe4(+) guest appears consistent with a quite striking compartmentalization phenomenon. ROESY NMR analyses showed that both sites exhibit a close spatial proximity with the hanging inner acetate groups, while a quantitative EXSY study revealed that these two sites are differentiated by their exchange rates. These NMR data support the hypothesis that these two inner sites could be delimited by the hanging inner acetate groups forming triangular (S1) or pentagonal (S2) hydrophobic pockets on the inner side of the capsule wall. Furthermore, the stability constants associated with the trapping process of the NMe4(+) guest on both the S1 and S2 sites have been determined, showing that the stability constant of the S1 sites decreases significantly as the concentration of the capsule increases gradually, while that of the S2 sites remains nearly unaffected. Such an observation has been interpreted as a result of the plugging process of the {Mo9O9} pores by the counterions NH4(+), which causes unfavorable electrostatic interactions for the NMe4(+) coordination on the proximal S1 site. Finally, the thermodynamic parameters of the NMe4(+) transfer from the solvated situation to the interior of the capsule were estimated from variable-temperature NMR experiments that provide the split of the global process into two successive events corresponding to the plugging and transfer across the inorganic shell.

This work illustrates how enthalpy and entropy changes responsible for successive phase transitions of cyanobiphenyl-based liquid crystals can be combined to give cohesive free energy densities. These new parameters are able to rationalize and quantify the demixing of the melting and clearing processes that occur in thermotropic liquid crystals. Minor structural variations at the molecular level can be understood as pressure increments that alter either the melting or clearing temperatures in a predictable way. This assessment of microsegregation operating in amphiphilic molecules paves the way for the chemical programming of the domain of existence of liquid-crystalline phases., (© 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)