Synthesis and characterization of molybdenum oxo complexes of two tripodal ligands: reactivity studies of a functional model for molybdenum oxotransferases

Reaction of the tetradentate ligand N-(2-hydroxybenzyl)-N,N-bis(2-pyridylmethyl)amine (L-OH) with MoO2Cl2 in methanol in the presence of NaOMe and PF6- results in the formation of [MoO2(L-O)]PF6. Similarly, the reaction of N-(2-mercaptobenzyl)-N,N-bis(2-pyridylmethyl)amine (L-SH) with MoO2(acac)2 leads to the formation of [MoO2(L-S)]+. The dioxo-molybdenum complex [MoO2(L-O)]+ reacts with phosphines in methanol to afford phosphine oxides and an air-sensitive molybdenum complex, tentatively identified as [Mo(IV)O(L-O)(OCH3)]. The latter complex is capable of reducing biological oxygen donors such as DMSO or nitrate, thereby mimicking the activity of DMSO reductase and nitrate reductase. Reaction of [MoO2(L-O)]PF6 with PPh3 in other solvents than methanol leads to the formation of the Mo(V) dimer [(L-O)OMo(micro-O)MoO(L-O)](PF6)2. The crystal structures of [MoO2(L-O)]PF6 and the micro-oxo bridged dimer are presented.     

Synthesis and characterization of trifluoromethyl fluoroformyl peroxycarbonate,CF3OC(O)OOC(O)F

The synthesis of CF(3)OC(O)OOC(O)F is accomplished by the photolysis of a mixture of (CF(3)CO)(2)O, FC(O)C(O)F, CO, and O(2) at -15 degrees C using a low-pressure mercury lamp. The new peroxide is obtained in pure form in low yield after repeated trap-to-trap condensation and is characterized by NMR, IR, Raman, and UV spectroscopy. Geometrical parameters were studied by ab initio methods [B3LYP/6-311+G(d)]. At room temperature, CF(3)OC(O)OOC(O)F is stable for many days in the liquid or gaseous state. The melting point is -87 degrees C, and the boiling point is extrapolated to 45 degrees C from the vapor pressure curve log p = 8.384 - 1715/T (p/mbar, T/K). A possible mechanism for the formation of CF(3)OC(O)OOC(O)F is discussed, and its properties are compared with those of related compounds.     

Fluid-like behavior of a one-dimensional granular gas

We study the properties of a one-dimensional (1D) granular gas consisting of N hard rods on a line of length L (with periodic boundary conditions). The particles collide inelastically and are fluidized by a heat bath at temperature Tb and viscosity gamma. The analysis is supported by molecular dynamics simulations. The average properties of the system are first discussed, focusing on the relations between granular temperature Tg=mv2, kinetic pressure, and density rho=N/L. Thereafter, we consider the fluctuations around the average behavior obtaining a slightly non-Gaussian behavior of the velocity distributions and a spatially correlated velocity field; the density field displays clustering: this is reflected in the structure factor which has a peak in the k approximately 0 region suggesting an analogy between inelastic hard core interactions and an effective attractive potential. Finally, we study the transport properties, showing the typical subdiffusive behavior of 1D stochastically driven systems, i.e., approximately Dt(1/2), where D for the inelastic fluid is larger than the elastic case. This is directly related to the peak of the structure factor at small wave vectors.     

12-Acylindolo[1,2-c]quinazolines by palladium-catalyzed cyclocarbonylation of o-alkynyltrifluoroacetanilides

6-Trifluoromethyl-12-acylindolo[1,2-c]quinazolines are prepared in high yield through the palladium-catalyzed reaction of bis(o-trifluoroacetamidophenyl)acetylene with aryl or vinyl halides and triflates. The reaction, which tolerates a variety of important functional groups, probably involves the formation of a 3-acyl-2-(o-trifluoroacetamidophenyl)indole intermediate, followed by its cyclization to the indoloquinazoline product. [reaction: see text]     

A liquid crystal derived from ­ruthenium(II,III) and a long‐chain carboxylate

The title compound, catena‐poly[[tetrakis(μ‐decanoato‐κ²O:O′)diruthenium(II,III)(Ru—Ru)]‐μ‐octanesulfonato‐κ²O:O′], [Ru₂(C₁₀H₁₉O₂)₄(C₈H₁₇O₃S)], is an octane­sulfonate derivative of the mixed‐valence complex diruthenium tetradecanoate. The equatorial carboxyl­ate ligands are bidentate, bridging two Ru atoms to form a dinuclear structure. Each of the two independent dinuclear metal complexes in the asymmetric unit is located at an inversion centre. The octane­sulfonate anion bridges the two dinuclear units through axial coordination. The alkyl chains of the carboxyl­ate and sulfonate ligands are arranged in a parallel manner. The global structure can be seen as infinite chains of polar moieties separated by a double layer of non‐polar alkyl groups, without interdigitation of the alkyl chains.     

Strengthening the Connection between Science,Society and Environment to Develop Future French and European Bioeconomies: Cutting-Edge Research of VAALBIO Team at UCCS

The development of the future French and European bioeconomies will involve developing new green chemical processes in which catalytic transformations are key. The VAALBIO team (valorization of alkanes and biomass) of the UCCS laboratory (Unité de Catalyse et Chimie du Solide) are working on various catalytic processes, either developing new catalysts and/or designing the whole catalytic processes. Our research is focused on both the fundamental and applied aspects of the processes. Through this review paper, we demonstrate the main topics developed by our team focusing mostly on oxygen- and hydrogen-related processes as well as on green hydrogen production and hybrid catalysis. The social impacts of the bioeconomy are also discussed applying the concept of the institutional compass.     

Open-shell localized Hartree-Fock method based on the generalized adiabatic connection Kohn-Sham formalism for a self-consistent treatment of excited states

An effective exact-exchange Kohn-Sham approach for the treatment of excited electronic states, the generalized adiabatic connection open-shell localized Hartree-Fock (GAC-OSLHF) method is presented. The GAC-OSLHF method is based on the generalized adiabatic connection Kohn-Sham formalism and therefore capable of treating excited electronic states, which are not the energetically lowest of their symmetry. The method is self-interaction free and allows for a fully self-consistent computation of excited valence as well as Rydberg states. Results for atoms and small- and medium-size molecules are presented and compared to restricted open-shell Hartree-Fock (ROHF) and time-dependent density-functional results as well as to experimental data. While GAC-OSLHF and ROHF results are quite close to each other, the GAC-OSLHF method shows a much better convergence behavior. Moreover, the GAC-OSLHF method as a Kohn-Sham method, in contrast to the ROHF approach, represents a framework which allows also for a treatment of correlation besides an exchange by appropriate functionals. In contrast to the common time-dependent density-functional methods, the GAC-OSLHF approach is capable of treating doubly or multiply excited states and can be easily applied to molecules with an open-shell ground state. On the nodal planes of the energetically highest occupied orbital, the local multiplicative GAC-OSLHF exchange potential asymptotically approaches a different, i.e., nonzero, value than in other regions, an asymptotic behavior which is known from exact Kohn-Sham exchange potentials of ground states of molecules.     

Identification of Folding Intermediates of Streblin,The Most Stable Serine Protease: Biophysical Analysis

Streblin, a serine proteinase from plant Streblus asper, has been used to investigate the conformational changes induced by pH, temperature, and chaotropes. The near/far UV circular dichroism activities under fluorescence emission spectroscopy and 8-aniline-1-naphthalene sulfonate (ANS) binding have been carried out to understand the unfolding of the protein in the presence of denaturants. Spectroscopic studies reveal that streblin belongs to the α+β class of proteins and exhibits stability towards chemical denaturants, guanidine hydrochloride (GuHCl). The pH-induced transition of this protein is noncooperative for transition phases between pH 0.5 and 2.5 (midpoint, 1.5) and pH 2.5 and 10.0 (midpoint, 6.5). At pH 1.0 or lower, the protein unfolds to form acid-unfolded state, and for pH 7.5 and above, protein turns into an alkaline denatured state characterized by the absence of ANS binding. At pH 2.0 (1 M GuHCl), streblin exists in a partially unfolded state with characteristics of a molten globule state. The protein is found to exhibit strong and predominant ANS binding. In total, six different intermediate states has been identified to show protein folding pathways.     

New phosphorylating reagents for deoxyribonucleosides and oligonucleotides

New phosphorylating reagents 1 and 2 were prepared in three steps from 4-hydroxybenzaldehyde. They showed good efficiency in the solid phase synthesis of 5′-phosphate monoester nucleosides. End-phosphate DNA sequence synthesis demonstrated the efficiency of the new reagents (1 and 2) according to the general procedure of automated DNA synthesis. The oxidation of P(III) to P(V) and the removal of benzyl protecting groups were achieved in a single step by treatment with a 0.02 M I₂/pyridine/H₂O solution. Due to this one-pot treatment, it is possible to use the phosphorylating reagents (1 and 2) for the synthesis of base-sensitive ODNs. The reagents 1 and 2 are unique among phosphorylating reagents.     

Field-induced π-polarization in barrelene derivatives: a computational study based on structural variation

Barrelene, H–C(CH=CH)₃C–H, is an unsaturated polycyclic hydrocarbon containing three isolated double bonds in a non-planar arrangement. We have studied the transmission of field effects through the barrelene framework by analyzing the small structural changes occurring in the phenyl group of many Ph–C(CH=CH)₃C–X molecules, where X is a variable substituent. Molecular geometries have been determined by quantum chemical calculations at the HF/6-31G* and B3LYP/6-311++G** levels of theory. Comparison with the results obtained for the corresponding saturated molecules, the bicyclo[2.2.2]octane derivatives Ph–C(CH₂–CH₂)₃C–X, reveals a small, but significant, field-induced π-polarization of the barrelene cage, especially when the remote substituent is a charged group. Additional evidence of π-polarization is obtained by comparing the electric dipole moments of the two sets of uncharged molecules. The structural variation of the barrelene cage caused by the variable substituent in Ph–C(CH=CH)₃C–X molecules has also been investigated. It is much larger than that of the phenyl group and depends primarily on the electronegativity of the substituent. Particularly pronounced is the concerted variation of the non-bonded distance between the bridgehead carbons of the cage, r(C···C) ₁ ^BARR , and the average of the three C–C–C angles at the cage carbon bonded to the variable substituent, α ₁ ^BARR . A scattergram of r(C···C) ₁ ^BARR versus the corresponding parameter for bicyclo[2.2.2]octane derivatives, r(C···C) ₁ ^BCO , shows that the variation of r(C···C) ₁ ^BARR becomes gradually less pronounced than that of r(C···C) ₁ ^BCO as the electronegativity of the substituent increases.