O conceito moderno de sociedade civil: do jusnaturalismo à economia política

Hegel’s Philosophy of Right presents civil society as the intermediate moment between family and State and as the privileged place of a peculiar kind of sociability connected with the subject of rights (person). The present paper explores how the three moments of Hegel’s civil society (the system of needs, the administration of justice and the police) were conceived in the second half of the eighteenth-century by the then new science of political economy. At the period, the term civil society was starting to be employed in a different way from the tradicional (where civil society is sinonimous to State), meaning a sphere organized around non-political principles demanding new conceptual tools.Partindo da teoria da eticidade de Hegel, onde a sociedade civil é apresentada como o momento intermediário entre a família e local privilegiado da sociabilidade própria ao sujeito de direitos (pessoa), o presente artigo explora o modo como os três momentos da sociedade civil (sistema de satisfação de carências, administração da justiça e polícia) foram teorizados ao longo da segunda metade do século XVIII pela então nascente economia política, compreendida aqui como um desdobramento da moderna teoria do direito natural. Paralelamente, investiga-se o modo como, nesse mesmo período, o termo sociedade civil começa a ser empregado por economistas com um significado diferente do tradicional e até então vigente (onde sociedade civil é sinônimo de Estado), designando uma esfera organizada a redor de princípios não políticos e cuja análise exige um novo aparato conceitual

Silylium Ion/Phosphane Lewis Pairs

The reactivity of a series of silylium ion/phosphane Lewis pairs was studied. Triarylsilylium borates <b>4</b>[B­(C₆F₅)₄] form frustrated Lewis pairs (FLPs) of moderate stability with sterically hindered phosphanes <b>2</b>. Some of these FLPs are able to cleave dihydrogen under ambient conditions. The combination of bulky trialkylphosphanes with triarylsilylium ions can be used to sequester CO₂ in the form of silylacylphosphonium ions <b>12</b>. The ability to activate molecular hydrogen by reaction of silylium ion/phosphane Lewis pairs is dominated by thermodynamic and steric factors. For a given silylium ion increasing proton affinity and increasing steric hindrance of the phosphane proved to be beneficial. Nevertheless, excessive steric hindrance leads to a breakdown of the dihydrogen-splitting activity of a silylium/phosphane Lewis pair

Correlation Between Charge Recombination and Lateral Hole-Hopping Kinetics in a Series of <i>cis</i>-Ru(phen′)(dcb)(NCS)₂ Dye-Sensitized Solar Cells

Four complexes of the general form <i>cis</i>-Ru­(phen′)­(dcb)­(NCS)₂, where dcb is 4,4′-(CO₂H)₂-2,2′-bipyridine and phen′ is 1,10-phenanthroline (phen), 4,7-(C₆H₅)₂-phen (Ph₂-phen), 4,7-(CH₃)₂-phen (Me₂-phen), or 3,4,7,8-(CH₃)₄-phen (Me₄-phen), were anchored to mesoporous TiO₂ thin films for applications as sensitizers in dye-sensitized solar cells (DSSCs). The compounds displayed metal based reductions <i>E</i>^o(Ru^III/II) = 1.01 ± 0.05 V vs NHE and were potent reductants competent of excited-state electron transfer to TiO₂ with yields ϕ_inj ≥ 0.75 in acetonitrile electrolytes. Average charge recombination rate constants, <i>k</i>_cr, abstracted from nanosecond transient absorption measurements, and the apparent diffusion coefficients for lateral hole-hopping, abstracted from chronabsorptometry measurements, showed the same sensitizer dependency: Ru­(Me₄-phen) > Ru­(Ph₂-phen) > Ru­(Me₂-phen) ≈ Ru­(phen). When used in operational solar cells, Ru­(Ph₂-phen) was most optimal with an efficiency of (6.6 ± 0.5)% in ionic liquids under 1 sun illumination. The superior performance of Ru­(Ph₂-phen) was traced to a higher injection yield and more efficient regeneration due to an unusually small sensitivity of <i>k</i>_cr to the number of injected electrons

Controlling Multicompartment Morphologies Using Solvent Conditions and Chemical Modification

The solution self-assembly of amphiphilic diblock copolymers into spheres, cylinders, and vesicles (polymersomes) has been intensely studied over the past two decades, and their morphological behavior is well understood. Linear ABC triblock terpolymers with two insoluble blocks A/B, on the other hand, display a richer and more complex morphological spectrum that has been recently explored by synthetic block length variations. Here, we describe facile postpolymerization routes to tailor ABC triblock terpolymer solution morphologies by altering block solubility (solvent mixtures), blending with homopolymers, and block-selective chemical reactions. The feasibility of these processes is demonstrated on polystyrene-<i>block</i>-polybutadiene-<i>block</i>-poly­(methyl methacrylate) (SBM) that assembles to patchy spherical micelles, which can be modified to evolve into double and triple helices or patchy and striped vesicles. These results demonstrate that postpolymerization treatments give access to a broad range of morphologies from single triblock terpolymers without the need for multiple polymer syntheses

Uranium(VI) Chemistry in Strong Alkaline Solution: Speciation and Oxygen Exchange Mechanism

The mechanism by which oxygen bound in UO₂ ²⁺ exchanges with that from water under strong alkaline conditions remains a subject of controversy. Two recent NMR studies independently revealed that the key intermediate species is a binuclear uranyl­(VI) hydroxide, presumably of the stoichiometry [(UO₂(OH)₄ ^2–)­(UO₂(OH)₅ ^3–)]. The presence of UO₂(OH)₅ ^3– in highly alkaline solution was postulated in earlier experimental studies, yet the species has been little characterized. Quantum-chemical calculations (DFT and MP2) show that hydrolysis of UO₂(OH)₄ ^2– yields UO₃(OH)₃ ^3– preferentially over UO₂(OH)₅ ^3–. X-ray absorption spectroscopy was used to study the uranium­(VI) speciation in a highly alkaline solution supporting the existence of a species with three U–O bonds, as expected for UO₃(OH)₃ ^3–. Therefore, we explored the oxygen exchange pathway through the binuclear adduct [(UO₂(OH)₄ ^2–)­(UO₃(OH)₃ ^3–)] by quantum-chemical calculations. Assuming that the rate-dominating step is proton transfer between the oxygen atoms, the activation Gibbs energy for the intramolecular proton transfer within [(UO₂(OH)₄ ^2–)­(UO₃(OH)₃ ^3–)] at the B3LYP level was estimated to be 64.7 kJ mol^–1. This value is in good agreement with the activation energy for “yl”–oxygen exchange in [(UO₂(OH)₄ ^2–)­(UO₂(OH)₅ ^3–)] obtained from experiment by Szabó and Grenthe (<i>Inorg. Chem.</i> <b>2010</b>, <i>49</i>, 4928–4933), which is 60.8 ± 2.4 kJ mol^–1. Both the presence of UO₃(OH)₃ ^3– and the scenario of an “yl”–oxygen exchange through a binuclear species in strong alkaline solution are supported by the present study

Spectroscopic Identification of Binary and Ternary Surface Complexes of Np(V) on Gibbsite

For the first time, detailed molecular information on the Np­(V) sorption species on amorphous Al­(OH)₃ and crystalline gibbsite was obtained by <i>in situ</i> time-resolved Attenuated Total Reflection Fourier-Transform Infrared (ATR FT-IR) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The results consistently demonstrate the formation of mononuclear inner sphere complexes of the NpO₂⁺ ion irrespective of the prevailing atmospheric condition. The impact of the presence of atmospheric equivalent added carbonate on the speciation in solution and on the surfaces becomes evident from vibrational data. While the 1:1 aqueous carbonato species (NpO₂CO₃^–) was found to become predominant in the circumneutral pH range, it is most likely that this species is sorbed onto the gibbsite surface as a ternary inner sphere surface complex where the NpO₂⁺ moiety is directly coordinated to the functional groups of the gibbsite’s surface. These findings are corroborated by results obtained from EXAFS spectroscopy providing further evidence for a bidentate coordination of the Np­(V) ion on amorphous Al­(OH)₃. The identification of the Np­(V) surface species on gibbsite constitutes a basic finding for a comprehensive description of the dissemination of neptunium in groundwater systems

Carbene Complexes of Stannocenes

Several stannocene carbene complexes, <b>3a</b>–<b>3g</b>, were synthesized and examined in solution by NMR spectroscopy and in the solid state by single-crystal X-ray diffraction. In this new class of metallocene carbene complexes, coordination of the carbene to the tin atom was found to be comparably weak and mostly due to attractive dispersion forces, as indicated by density functional theory calculations. Furthermore, coordination of the N-heterocyclic carbenes results in a weakening of the Sn–Cp bonds, making these complexes very reactive and short-lived at room temperature

Cyclic Silylated Onium Ions of Group 15 Elements

Five- and six-membered cyclic silylated onium ions of group 15 elements <b>I</b> were synthesized by intramolecular cyclization of transient silylium ions <b>II</b>. Silylium ions <b>II</b> were prepared by the hydride transfer reaction from silanes <b>III</b> using trityl cation as hydride acceptor. It was found that smaller ring systems could not be obtained by this approach. In these cases tritylphosphonium ions <b>IV</b> were isolated instead. Cations <b>I</b> and <b>IV</b> were isolated in the form of their tetrakispentafluorphenyl borates and characterized by multinuclear NMR spectroscopy and, in two cases, by X-ray diffraction analysis. Cyclic onium ions <b>I</b> showed no reactivity similar to that of isoelectronic intramolecular borane/phosphane frustrated Lewis pairs (FLPs). The results of DFT computations at the M05-2X level suggest that the strength of the newly formed Si–E linkage is the major reason for inertness of <b>I</b>[B­(C₆F₅)₄] versus molecular hydrogen

Hidden Structural Features of Multicompartment Micelles Revealed by Cryogenic Transmission Electron Tomography

The demand for ever more complex nanostructures in materials and soft matter nanoscience also requires sophisticated characterization tools for reliable visualization and interpretation of internal morphological features. Here, we address both aspects and present synthetic concepts for the compartmentalization of nanoparticle peripheries as well as their <i>in situ</i> tomographic characterization. We first form negatively charged spherical multicompartment micelles from ampholytic triblock terpolymers in aqueous media, followed by interpolyelectrolyte complex (IPEC) formation of the anionic corona with bis-hydrophilic cationic/neutral diblock copolymers. At a 1:1 stoichiometric ratio of anionic and cationic charges, the so-formed IPECs are charge neutral and thus phase separate from solution (water). The high chain density of the ionic grafts provides steric stabilization through the neutral PEO corona of the grafted diblock copolymer and suppresses collapse of the IPEC; instead, the dense grafting results in defined nanodomains oriented perpendicular to the micellar core. We analyze the 3D arrangements of the complex and purely organic compartments, <i>in situ</i>, by means of cryogenic transmission electron microscopy (cryo-TEM) and tomography (cryo-ET). We study the effect of block lengths of the cationic and nonionic block on IPEC morphology, and while 2D cryo-TEM projections suggest similar morphologies, cryo-ET and computational 3D reconstruction reveal otherwise hidden structural features, <i>e.g.</i>, planar IPEC brushes emanating from the micellar core

Enzymatic Synthesis and Surface Deposition of Tin Dioxide using Silicatein-α

Nanostructured tin dioxide was synthesized by making use of the catalytic activity of silicatein-α. TEM, HRTEM, and XRD revealed the formation of cassiterite SnO₂. Surface bound silicatein retains its biocatalytic activity. This was demonstrated by immobilizing silicatein on glass surfaces using a histidine-tag chelating anchor. The subsequent deposition of SnO₂ on glass was monitored by quartz crystal microbalance (QCM) measurements and scanning electron microscopy (SEM). This new aspect of silicatein activity toward the formation of metal oxides other than SiO₂, TiO₂, and BaTiO₃ opens up new vistas in composite material synthesis