Elaboration of hybrid nanocluster materials by solution chemistry

The [(M₆L₁₂ⁱ)L₆^a]ⁿ⁻ and [(M₆L₈ⁱ)L₆^a] units (a = apical, i = inner) constitute the basic building blocks in the octahedral cluster chemistry. Nano-sized metallic clusters are easily obtained by solid state synthesis with transition elements associated with halogen or chalcogen. The intrinsic properties of M₆ cluster units—one or two electron reversible redox process, magnetism and luminescence—depend on the nature of the metal and ligands. The solubilisation of M₆ solid state compounds provides [(M₆L₁₂ⁱ)L₆^a]ⁿ⁻ or [(M₆L₈ⁱ)L₆^a]ⁿ⁻ building blocks with individual properties that can be further used for the design of hybrid organic/inorganic materials. Several examples of solid state precursors are presented as well as substitution reactions of apical ligands in solution. Indeed, hexacyano M₆ clusters are obtained by direct reaction of solid state precursors in aqueous KCN solutions. Low dimensional frameworks are subsequently obtained by recrystallisation of hexacyano M₆ clusters with transition elements. The functionalisation of cluster proceeds in two steps. The first one consists in the replacement of apical halogens of cluster unit precursors by labile groups as CF₃SO₃ (triflate) or solvent molecules after solution reaction. The second one consists in the substitution of the labile groups by functionalised phenolate or pyridine ligands.     

Aldol condensations over reconstructed Mg-Al hydrotalcites: structure-activity relationships related to the rehydration method

Two different rehydration procedures in the liquid or gas phase have been applied to reconstruct mixed oxides derived from calcined hydrotalcite-like materials to be used as catalysts for aldol condensation reactions. The as-synthesized hydrotalcite, its decomposition product, as well as the reconstructed solids upon rehydration were characterized by XRD, N(2) adsorption, He pycnometry, FTIR, SEM, TEM, (27)Al MAS-NMR and CO(2)-TPD (TPD=temperature-programmed desorption). Compared to the Mg-Al mixed oxide rehydrated in the gas phase (HT-rg), that rehydrated in the liquid phase (HT-rl) exhibits a superior catalytic performance with respect to the aldol condensation of citral with ketones to yield pseudoionones and in the self-aldolization of acetone. The textural properties of HT-rl and HT-rg differ strongly and determine the catalytic behavior. A memory effect led to a higher degree of reconstruction of the lamellar structure when the mixed oxide was rehydrated in the gas phase rather than in the liquid phase, although liquid-phase rehydration under fast stirring produced a surface area that was 26 times greater. This contrasts to typical statements in the literature claiming a higher degree of reconstruction in the presence of large amounts of water in the medium. CO(2)-TPD shows that the number of OH(-) groups and their nature are very similar in HT-rg and HT-rl, and cannot explain the markedly different catalytic behavior. Accordingly, only a small fraction of the available basic sites in the rehydrated samples is active in liquid-phase aldol condensations. Our results support the model in which only basic sites near the edges of the hydrotalcite platelets are partaking in aldol reactions. Based on this, reconstructed materials with small crystallites (produced by exfoliation during mechanical stirring), that is, possessing a high external surface area, are beneficial in the reactions compared to larger crystals with a high degree of intraplatelet porosity.     

Synthesis,Characterization and Theoretical Study of the Chemical Reactivity of New Cyclic Sulfamides Linked to Tetrathiafulvalene

Abstract

The synthesis of the title compounds has been carried out by condensation via a Wittig-type reaction of a pyridinium hexafluorophosphate with a phosphonate ester to give the desired (4-nitrophenyl)tetrathiafulvalene the nitro group of which was reduced to an amino group. Reaction of the amine with chlorosulfonyl isocyanate and subsequently with tert-butyl alcohol gave the corresponding open-chain sulfamide. Cyclization under basic conditions and de-protection led to 2-[4-(4′,5′-dipropyltetrathiafulvalen-4-yl)]phenyl-1,2,6-thiadiazinane 1,1-dioxide. Finally, N-alkylated and N-acylated cyclic sulfamides linked to tetrathiafulvalene were obtained. Their electron donor ability was measured by cyclic voltammetry. A detailed DFT study based on B3LYP/6–31G (d,p) of electronic properties is also presented. The calculated molecular electrostatic potential shows that, the negative charge covers the nitro and sulfamide function, while positive charge is located at the hydrogen atoms of the amine and sulfamide rings. The calculated HOMO and LUMO energy reveals that charge transfer occurs within the molecule. The chemical reactivity parameters reveal that tetrathiafulvalene 1 is highly reactive, which facilitates the desired formation of the cyclic sulfamide. The first hyperpolarizability β_tot shows that compounds 1 and 5 are good candidates as a NLO material.     

SYNTHESIS OF MONO-AND DIALKYLPHOSPHATES BY THE REACTIONS OF HYDROXYCOMPOUNDS WITH THE PHOSPHORUS PENTAOXIDE UNDER MICROWAVE IRRADIATION

The reactions of phosphorus pentoxide with two alcohols and one phenol were performed in different conditions under microwave irradiation. The products (alkylphosphates and dialkylphosphates) were identical to those formed by classic heating and were obtained with better yields. The speed of the reaction was increased by a factor from 100 to 4000.     

A serendipitous conversion of enaminolactone nitriles with primary amines: a new synthesis of substituted 2-aminopyridine derivatives

In the course of our studies on Cerpegin analogues synthesis, a serendipitous reactivity of enaminolactone nitrile has been observed. Instead of expecting iminocerpegins, we have gained new class of substituted 2-aminopyridines. The methodology has been applied on a wide range of primary amines, as aliphatic, aromatic, heteroaromatic and also, diamines, hydrazines and chiral amines.     

Investigation of 7-((dioctylamino)methyl)quinoline-8-ol for uptake and removal of uranyl ions

A new 8-hydroxyquinoline derivative extractant was synthesized via the Mannich reaction from a secondary amine. Various analytical techniques (¹H, ¹³C NMR, FTIR, mass spectroscopy) were used to characterize our product. The use of this new extractant for the uptake and removal of uranyl ions in aqueous solution was investigated. Conditions for an effective sorption were optimized with respect to different experimental parameters in batch process. The results showed that the extraction rate increases for solutions with a pH in the range [0.65–1.13]. The total sorption capacity was 105 (mg g^?1) under optimum experimental conditions. The extraction of UO₂ ²⁺ was found to be quantitative (100 %) at initial uranyl concentration less than or equal to 41.59 mg/L. Thermodynamic parameters showed the adsorption of an endothermic process and a spontaneous nature, respectively.     

Cyclometalated AuIII Complexes for Cysteine Arylation in Zinc Finger Protein Domains: towards Controlled Reductive Elimination

With the aim of exploiting the use of organometallic species for the efficient modification of proteins through C-atom transfer, the gold-mediated cysteine arylation through a reductive elimination process occurring from the reaction of cyclometalated Au^III C^N complexes with a zinc finger peptide (Cys₂His₂ type) is here reported. Among the four selected Au^III cyclometalated compounds, the [Au(C^CON)Cl₂] complex featuring the 2-benzoylpyridine (C^CON) scaffold was identified as the most prone to reductive elimination and Cys arylation in buffered aqueous solution (pH 7.4) at 37 °C by high-resolution LC electrospray ionization mass spectrometry. DFT and quantum mechanics/molecular mechanics (QM/MM) studies permitted to propose a mechanism for the title reaction that is in line with the experimental results. Overall, the results provide new insights into the reactivity of cytotoxic organogold compounds with biologically important zinc finger domains and identify initial structure–activity relationships to enable Au^III-catalyzed reductive elimination in aqueous media.     

Diamondoid Nanostructures as sp3‐Carbon‐Based Gas Sensors

Diamondoids, sp³‐hybridized nanometer‐sized diamond‐like hydrocarbons (nanodiamonds), difunctionalized with hydroxy and primary phosphine oxide groups, enable the assembly of the first sp³‐C‐based chemical sensors by vapor deposition. Both pristine nanodiamonds and palladium nanolayered composites can be used to detect toxic NO₂ and NH₃ gases. This carbon‐based gas sensor technology allows reversible NO₂ detection down to 50 ppb and NH₃ detection at 25–100 ppm concentration with fast response and recovery processes at 100 °C. Reversible gas adsorption and detection is compatible with 50 % humidity conditions. Semiconducting p‐type sensing properties are achieved from devices based on primary phosphine–diamantanol, in which high specific area (ca. 140 m² g^?1) and channel nanoporosity derive from H‐bonding.     

Potassium Fluoride on Alumina: Condensation of 1,4-Diacetylpiperazine-2,5-Dione with Aldehydes. Dry Condensation Under Microwave Irradiation. Synthesis of Albonursin and Analogues

1,4-Diacetylpiperazine-2,5-dione (1) was condensated with aldehydes (2) with KF on alumina without solvent under microwaves or in at room temperature in the presence of DMF. The reaction was stereoselective and some natural products (4a-c) like albonursin(4c) were synthesized.     

Clay Catalysis: Stork's Alkylation and Acylation of Cyclohexanone Without Isolation of Enamine

Cyclohexanone and morpholine in the presence of KSF under azeotropic distillation gave 1-morpholinocyclohexene which is alkylated or acylated in situ without isolation of the enamine. The overall yield of these Stork's reactions are better or equivalent to those obtained by isolation of the enamine.