Nitric Oxide Disproportionation Mediated by a Rh Complex with an Asymmetric Pincer Ligand: Spectroscopic Detection of a Dinitrosyl Intermediate

The disproportionation of nitric oxide was studied by FTIR with two different Rh(I)PCN complexes as mediators (PCN 1-((diethylamino)methyl)-3-((di-tertbutylphosphino)methyl)-benzene). As had already been reported for a PCP analogue, reaction yielded a Rh(PCN)(NO)(NO₂) complex along with gaseous N₂O in both cases. However, when [Rh(PCN)(NO)]⋅ was used as a reactant, FTIR monitoring allowed for the detection of signals of a reaction intermediate, coherent with the expected but seldom reported dinitrosyl species Rh(PCN)(NO)(NO). DFT studies on this species revealed that pincer hemilability of the amino arm is involved in its stabilization, therefore accounting for the differences observed in reactivity between PCN and PCP.     

Metastable Dissociation of Anions Formed by Electron Attachment

A comprehensive analysis of metastable dissociation of 2,4‐dinitrotoluene (DNT) parent anions formed by attachment of electrons of controlled energy is presented. We characterize the energy dependence and kinetic energy release of the reaction which competes with autodetachment. A surprising finding is a highly exothermic metastable reaction triggered by the attachment of thermal electrons which we relate to the well‐known electrostatic ignition hazards of DNT and other explosives. Quantum chemical calculations are performed for dinitrobenzene in order to elucidate the process of NO abstraction.     

Polydimethylsiloxane-LiNbO3 surface acoustic wave micropump devices for fluid control into microchannels

This paper presents prototypical microfluidic devices made by hybrid microchannels based on piezoelectric LiNbO(3) and polydimethylsiloxane. This system enables withdrawing micropumping by acoustic radiation in microchannels. The withdrawing configuration, integrated on chip, is here quantitatively investigated for the first time, and found to be related to the formation and coalescence dynamics of droplets within the microchannel, primed by surface acoustic waves. The growth dynamics of droplets is governed by the water diffusion on LiNbO(3), determining the advancement of the fluid front. Observed velocities are up to 2.6 mm s(-1) for 30 dBm signals applied to the interdigital transducer, corresponding to tens of nl s(-1), and the micropumping dynamics is described by a model taking into account an acoustic power exponentially decaying upon travelling along the microchannel. This straighforward and flexible micropumping approach is particularly promising for the withdrawing of liquids in lab-on-chip devices performing cycling transport of fluids and biochemical reactions.     

Ligand-mediated decarbonylation as an efficient synthetic method to Re(I) and Re(II) dicarbonyl complexes

A novel synthetic method based on a ligand-mediated decarbonylation reaction of complexes of the common fac-[Re(CO)3]+ core efficiently yields Re(I) and Re(II) dicarbonyl species.     

Conus ventricosus venom peptides profiling by HPLC-MS: a new insight in the intraspecific variation

Conus is a genus of predatory marine gastropods that poison the prey with a complex mixture of compounds active on muscle and nerve cells. An individual cone snail's venom contains a mixture of pharmacological agents, mostly short, structurally constrained peptides. This study is focused on the composition of the venom employed by Conus ventricosus Gmelin, 1791, a worm-hunting cone snail living in the Mediterranean Sea. For this purpose, LC coupled to MS techniques has been successfully used to establish qualitative and quantitative differences in conopeptides from minute amounts of venom ducts. We were able to prove variability in the venom conopeptide complement, possibly related to different trophic habits of the species in the Mediterranean Sea. Moreover, the information-rich MS techniques enabled us to identify two novel C. ventricosus peptides, here named Conotoxin-Vn and -Conotoxin-Vn. On the basis of the structural data collected so far, we suggest that Conotoxin-Vn is a conopeptide belonging to the -family that recognizes calcium channels through a specific pharmacophore. Similarly, molecular modeling data suggest that -Conotoxin-Vn should represent a competitive antagonist of neuronal nicotinic acetylcholine receptors (nAChRs).     

Pressure-induced core packing and interfacial dehydration in nonionic C12E6 micelle in aqueous solution

A spherical micelle of C12E6 is simulated at different pressures, from 0.001 to 3 kbar, by molecular dynamics. On increasing the pressure the alkyl tails of the surfactants pack tightly and stretch. At 3 kbar we observe dynamical slowing down of the oil core of the micelle. At that pressure the core is characterized by a high oil density, rho oil approximately 0.85 g/cm(3), regular density oscillation, and low chain entropy. Pressure affects the interfacial region as well. Dehydration, induced by the collapse of the hydrophilic head groups, is observed in the inner part of the interface. Such dehydration resembles temperature dehydration but differs in details. Our results support the interpretation of recent experiments on micellar solutions at high pressure.     

Synthesis and characterization of epoxy-modified cement slurries--kinetic data at hardened slurries/HCl interfaces

In this study, two new epoxy-modified oilwell cement slurries were synthesized. All characterization measurements were performed and compared in relation to a standard cement slurry, which was synthesized using only cement and water. The XRD patterns, as well as TG/DTG and DSC analyses have suggested that portlandite (Ca(OH)2) and carbonate phases were not present in detectable amounts in the new cement slurries. The isothermal kinetic data of the interaction of HCl with the epoxy-modified cement were obtained using the batch mode from 25 to 55 degrees C. The kinetic data were best fitted to the second-order and the Avrami kinetic models, since differences between experimental and calculated values were lower for these models. The intraparticle diffusion model has pointed out that the new slurries present positive values for the parameter "C," which is related to higher boundary layer resistance to HCl diffusion into the internal parts of the slurries, in relation to the standard slurry. The characterization and the HCl interaction kinetic studies have suggested that the new cement slurries present good potential, from the chemical viewpoint, to be used in oilwell operations.     

Electrokinetics in nanochannels: part II. Mobility dependence on ion density and ionic current measurements

In the first of this two-paper series, a new model was developed for calculating the electric potential field in a long, thin nanochannel with overlapped electric double layers. The model takes into account the dependence of ion mobility on local ion densities and pH. This model is used here to study and demonstrate the effect of ion density and pH on ionic current measurements. A comparison is shown of predictions based on each of three boundary conditions, as studied in Part I. The model developed in Part I is validated by comparing simulations with measurements of ionic current as a function of sodium borate concentration. Results show that predictions based on extended Debye-Hückel theory for ion mobility significantly improve the accuracy of simulations, but that these do not predict exact scaling behavior. A simple bulk conductivity measurement used as input parameter for the simulations, in place of the predicted bulk conductivity (K(0)), guarantees agreement with data in the thin EDL region. Results also indicate that the charge regulation boundary condition, complemented with an adequate bulk electrolyte model, provides better agreement with experimental trends than the specified zeta potential or specified surface net charge boundary conditions. Further, it is shown that currents due to advection (by electroosmotic flow) are in all cases studied less than 25% of the total current in the system.     

Direct palladium-catalyzed C-3 arylation of free (NH)-indoles with aryl bromides under ligandless conditions

A new method for the efficient, practical, and highly regioselective direct palladium-catalyzed C-3 arylation of free (NH)-indole and its electron-rich 1-unsubstituted derivatives under ligandless conditions is described. The reactions, which are run outside a glovebox without purification of solvent and reagents, involve treatment of free (NH)-indoles with activated, unactivated, and deactivated aryl bromides in refluxing toluene in the presence of K2CO3 as the base and a catalyst system consisting of a combination of Pd(OAc)2 and benzyl(tributyl)ammonium chloride. The experimental results are consistent with a catalytic cycle based on an electrophilic palladation pathway at the 3-position of 1-indolyl potassium salts.