Concise and diversity-oriented synthesis of ligand arm-functionalized azoamides

Azoamides, previously established as bioactive intracellular GSH-depleting agents, were decorated with a terminal alkyne moiety to 4 and then were transformed, by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), into different ligand-arm functionalized azoamides 6. Azides 5 having ligand-arms amenable for binding to platinum(II) were selected for this study. Because, for the fragile azoamides 4, the typically employed reaction conditions for CuAAC failed, several alternative solvents and copper catalysts were tested. Excellent results were obtained with copper(II) sulfate pentahydrate/metallic copper and especially with heterogeneous catalysts, such as copper-in-charcoal, cupric oxide, and cuprous oxide. The heterogeneous catalysts were employed to obtain the desired products in almost quantitative yields by a simple three-step "stir-filter-evaporate" protocol with no or negligible contamination with copper impurities. This is of particular importance because compounds 6 have been designed for coordination.     

Simulation of tunneling in enzyme catalysis by combining a biased propagation approach and the quantum classical path method: application to lipoxygenase

The ability of using wave function propagation approaches to simulate isotope effects in enzymes is explored, focusing on the large H/D kinetic isotope effect of soybean lipoxygenase-1 (SLO-1). The H/D kinetic isotope effect (KIE) is calculated as the ratio of the rate constants for hydrogen and deuterium transfer. The rate constants are calculated from the time course of the H and D nuclear wave functions. The propagations are done using one-dimensional proton potentials generated as sections from the full multidimensional surface of the reacting system in the protein. The sections are obtained during a classical empirical valence bond (EVB) molecular dynamics simulation of SLO-1. Since the propagations require an extremely long time for treating realistic activation barriers, it is essential to use an effective biasing approach. Thus, we develop here an approach that uses the classical quantum path (QCP) method to evaluate the quantum free energy change associated with the biasing potential. This approach provides an interesting alternative to full QCP simulations and to other current approaches for simulating isotope effects in proteins. In particular, this approach can be used to evaluate the quantum mechanical transmission factor or other dynamical effects, while still obtaining reliable quantized activation free energies due to the QCP correction.     

A structural and corrosion study of triethoxysilyl functionalized POSS coatings on AA 2024 alloy

A novel bifunctional polyhedral oligomeric silsesquioxane (POSS) based silane precursor R(x)R'(y)(SiO(3/2))(8), (x + y = 8), bearing 3-(N-(3-triethoxysilylpropyl)ureido)propyl (ureasil - U) and isooctyl (IO) groups (i.e., U(2)IO(6) POSS) was synthesized, and the corresponding coatings, prepared under the acid hydrolysis conditions, were studied in order to assess their corrosion inhibition of the AA 2024-T3 alloy. The U(2)IO(6) POSS precursor was made in two steps: in the first, an appropriate stoichiometric (2:6) mixture of 3-aminopropyltriethoxysilane (AP(2)) and isooctyltrimethoxysilane (IO(6)) was autoclaved under basic hydrolysis conditions giving AP(2)IO(6)(SiO(3/2))(8) cubes, which were reacted in the second step with 3-isocyanatopropyltriethoxysilane (ICPTES), leading to the bis end-capped sol-gel precursor U(2)IO(6) POSS having a cube-like structure. Coatings were made from sols catalyzed with acidified water. IR and (29)Si NMR spectroscopic studies combined with mass spectrometric measurements were employed to confirm the cube-like structure of AP(2)IO(6) and U(2)IO(6) POSS. The structure and morphology of the U(2)IO(6) POSS coatings were studied with the help of infrared reflection-absorption (IR RA) spectroscopic measurements combined with XPS and AFM measurements, providing information about the formation of partially self-assembled coatings. The degree of corrosion inhibition was assessed from the potentiodynamic measurements showing around 10 times smaller current densities for the coatings only 30-40 nm thick. Ex situ IR RA spectroelectrochemical measurements were performed by consecutive measurements of the IR RA spectra of U(2)IO(6) POSS coatings which were chronocoulometrically charged at different potentials. At potentials more positive than the corrosion potential (E(corr) approximately -0.5 V), the amide I bands shifted, indicating the formation of new urea-urea aggregations and associations, with the newly formed strong band at 1680-1690 cm(-1) suggesting the formation of amidonium ions. These results showed that the urea groups represented the weakest part of the coatings due to their tendency to protonation.     

Oxidation of sulfides including DBT using a new vanadyl complex of a non‐innocent o‐aminophenol benzoxazole based ligand

Reaction of a non‐innocent o‐aminophenol benzoxazole based ligand HL^BAP with VOCl₃ afforded a vanadyl complex, VOL^BIS (SQ), in which SQ is a 2,4‐di‐tert‐butylsemiquinone produced from hydrolysis of HL^BAP. The crystal structure of VOL^BIS (SQ) exhibits an octahedral geometry with the VO²⁺ center coordinated by two nitrogen and one oxygen atoms of L^BAP and two oxygen atoms of SQ. Electrochemical studies showed quasi‐reversible metal‐centered reduction and ligand‐centered oxidation of complex. The magnetic moment of VOL^BIS (SQ) is consistent with the spin‐only value expected for S = 1/2 system. The neutral species of VOL^BIS (SQ) is EPR active, which is consistent with a paramagnetic electronic ground state (S = 1/2). This result is in accordance with the vanadyl (IV) moiety surrounded by tridentate iminobenzosemiquinonate anion radical (HL^BIS)^?‐ and benzosemiquinone ligand (SQ)^?. The theoretical calculations confirm the experimental results. Furthermore, we present the optimal conditions for maximum efficiency of sulfide oxidation for oxidative desulfurization with hydrogen peroxide and 6 times reusability of catalyst for sulfoxidation of dibenzothiophene.     

On isomorphisms of algebras of smooth functions

We show that for any smooth Hausdorff manifolds and , which are not necessarily second-countable, paracompact or connected, any isomorphism from the algebra of smooth (real or complex) functions on to the algebra of smooth functions on is given by composition with a unique diffeomorphism from to . An analogous result holds true for isomorphisms of algebras of smooth functions with compact support.

     

Acoustic wave transmission through piezoelectric structured materials

This paper deals with the transmission of acoustic waves through multilayered piezoelectric materials. It is modeled in an octet formalism via the hybrid matrix of the structure. The theoretical evolution with the angle and frequency of the transmission coefficients of ultrasonic plane waves propagating through a partially depoled PZT plate is compared to finite element calculations showing that both methods are in very good agreement. The model is then used to study a periodic stack of 0.65PMN-0.35PT/0.90PMN-0.10PT layers. The transmission spectra are interpreted in terms of a dispersive behavior of the critical angles of longitudinal and transverse waves, and band gap structures are analysed. Transmission measurements confirm the theoretical calculations and deliver an experimental validation of the model.     

Influence of substituents on the anharmonicity of nus(OH) vibration in phenol derivatives explored by experimental and theoretical approach

Very good reproducibility of the first five vibrational transitions of phenol in the gas phase by the MP2/ 6-31G potential for O-H bond stretching was found. The vibrational levels were calculated by a program for variational solving of the time-independent Schr?dinger equation in one dimension. Relative intensities of particular transitions were determined on the basis of the function of the dipole moment. The substituent effects on the nu(s)(OH) transitions and on the intensity of these transitions, as well as on the structure of eleven phenols, was analyzed as a function of the pK(a) values.     

Functoriality of the Bimodule Associated to a Hilsum–Skandalis Map

We extend the functoriality of the Connes convolution algebra to the category of Hilsum–Skandalis maps between separated smooth étale groupoids. Thereby we establish that Morita equivalent separated smooth étale groupoids have Morita equivalent convolution algebras, analogously to the results of Muhly, Renault and Williams, and others, on the C^*algebras of Morita equivalent groupoids.     

75As N.Q.R. and 19F N.M.R. study of solid AsF3

The temperature dependence of the ⁷⁵As pure quadrupole resonance frequency in AsF₃ has been studied from 77 K to a temperature very close to the melting point. It is found that the effective electric field gradient at the As site does not shift much from the gas-phase value and that the temperature dependence of the ⁷⁵As N.Q.R. frequency seems to follow the Bayer-Kushida model. The occurrence of a line-width transition in the ¹⁹F N.M.R. spectrum between 200 and 150 K demonstrates the presence of low-frequency, large-amplitude molecular motions which are too slow to average out the ⁷⁵As quadrupole coupling.