Роль релігійних цінностей у процесі формування права

У контексті з’ясування основних пріоритетів розвитку права розглядається проблема ролі релігійних цінностей як основи розвитку права. Показано взаємодію релігії і права в умовах мінливої динаміки демократизації українського суспільства, обгрунтовано пріоритетні моральні принципи для побудови фундаменту, на якому грунтується і завдяки якому розвивається право. Ключові слова: релігійні цінності, цінності права, мораль.В контексте определения основных приоритетов развития права рассматривается проблема роли религиозных ценностей как базиса развития права. Показано взаимодействие религии и права в условиях изменчивой динамики демократизации украинского общества, обоснованы приоритетные моральные принципы для строительства фундамента, на котором основывается и благодаря которому развивается право. Ключевые слова: религиозные ценности, ценности права, мораль.It is reviewed the issue of rule of religious values as a basis and grounds for law evolution in the context of definition of its main priorities. It is shown the correlation between the religion and the law in circumstances of possible dynamic of Ukrainian society democratization. It is обосновано the priority moral principles for developing pivot as a ground of law evolution. Key words: «religion values», «values of law», «moral»

«Національна згода» як об’єкт філософської рефлексії

У статті розглядається концепт «національної згоди» як певний різновид комунікації між владою та громадськістю. Виділяються основні типи соціальної згоди: «згода» як легітимізація влади з боку населення, «згода» як певний різновид ідентичності («національна згода»), «згода» як консенсус стосовно проведення тієї чи іншої політики.The author reviews a concept of «national consent» as a variety of communication between power and community. The basic types of social consent are determined: consent as legitimization of power on the part of society, consent as a definite variety of identity («national consent»), consent as a consensus in politics

An unprecedented phosphinine with significant P(π)-donor properties

A hitherto unprecedented electronic situation has been observed for a substituted, pyridyl-functionalized phosphinine. In contrast to previous studies, this compound shows considerable π-donor properties as the result of the rather strong +M effect of the CH3S-substituent, changing the electronic properties of this low-coordinate and aromatic phosphorus heterocycle substantially

The Role of Culture in Business Transaction:Implications for Success in Trans-Geographical Settings

Non-oxidative dehydroaromatization of methane (MDA) is a promising catalytic process for direct valorization of natural gas to liquid hydrocarbons. The application of this reaction in practical technology is hindered by a lack of understanding about the mechanism and nature of the active sites in benchmark zeolite-based Mo/ZSM-5 catalysts, which precludes the solution of problems such as rapid catalyst deactivation. By applying spectroscopy and microscopy, it is shown that the active centers in Mo/ZSM-5 are partially reduced single-atom Mo sites stabilized by the zeolite framework. By combining a pulse reaction technique with isotope labeling of methane, MDA is shown to be governed by a hydrocarbon pool mechanism in which benzene is derived from secondary reactions of confined polyaromatic carbon species with the initial products of methane activation

Chemical reactivity of cation-exchanged zeolites

Zeolites modified with metal cations have been extensively studied during the last two decades because of their wide application in different technologically important fields such as catalysis, adsorption and gas separation. Contrary to the well-understood mechanisms of chemical reactions catalyzed by Brønsted acid sites in the hydrogen forms of zeolites, the nature of chemical reactivity, and related, the structure of the metal-containing ions in cation-exchanged zeolites remains the subject of intense debate. In this thesis, the chemical properties of zeolites modified with hard Lewis acids such as alkaline- and alkali-earth cations (Chapters 2 – 4) and with soft Lewis acids such as Zn-, Cd- and Ga-cations (Chapters 5 – 9) are discussed. Special attention is paid to the mechanism of chemical transformations promoted by such exchangeable species and, accordingly, their role in these processes. Low-silica zeolites modified with alkaline- and alkali-earth cations are rather inert materials. However, it has been experimentally found that they can efficiently promote photo-oxidation of unsaturated hydrocarbons with molecular oxygen. The details of this reactivity are not clear. Chapter 2 reports DFT calculations on the initial charge-transfer step for alkene photo-oxidation in zeolite Y modified with alkali-earth cations (Mg, Ca, and Sr). The photo-oxidation of 2,3-dimethyl-2-butene (DMB) with O2 has been used as a model reaction. It is predicted that the electrostatic field of the zeolite cavity plays only a minor role for the stabilization of the charge-transfer state, while the relative orientation and the distance between the adsorbed alkene and oxygen molecules are the critical factors. A high density and specific location of the exchangeable cations in the zeolite matrix determines a specific confinement of the adsorbed reagents in a suitable "pre-transition state" configuration. The optimum configuration of co-adsorbed DMB and O2 molecules is identified for CaY zeolite. A significantly lower activity of SrY and MgY in the photooxidation of 2,3-dimethyl-2-butene-2 in comparison with that of CaY is predicted. Another interesting property of low-silica zeolites modified with alkaline cations is their ability to promote N2O4 disproportionation under very mild conditions. Chapter 3 presents periodic DFT calculations on N2O4 disproportionation in Na-, K-, and Rb-exchanged lowsilica zeolite X. The disproportionation reaction results in rather polar NO+···NO3 – species, which are effectively stabilized by the cage of cation-exchanged zeolite. NO+ binds to the basic framework oxygens, and NO3 – anion coordinates to the exchangeable cations. Although the binding energy of NO+ ion to the zeolite is influenced by the basicity of the framework, the theoretical results show that the overall disproportionation reaction is mainly controlled by the interactions between the negatively charged nitro group and the extra-framework cations. The role of the interaction between the nitrosonium cation and basic sites of the zeolite is only of minor importance. The function of the microporous matrix is to facilitate the charge separation in a fashion similar to that of a polar solvent. It is concluded that steric properties of the zeolite cage, the cooperative effect of the extraframework cations as well as their mobility induced by adsorption are essential to form the optimum configuration of the active site for N2O4 disproportionation. Chapter 4 reports a combined infrared spectroscopic and computational study of light alkane adsorption to alkali-earth exchanged zeolite Y. Although these materials do not catalyze C–H or C–C bond cleavage, they can be successfully used as model adsorbents to investigate the factors influencing structural and electronic properties of the resulting adsorption complexes. The experimental IR spectra of the C–H stretching vibrations of the adsorbed hydrocarbons differ strongly for MgY and CaY zeolites. On the basis of ab initio MP2 and DFT calculations it is found that different geometries of the light alkane adsorption complexes are realized depending on the cation in the adsorption site. Topological analysis of the electron density distribution function in the framework of quantum theory of atoms in molecules is applied to investigate the bonding of the adsorption complexes. It is found that numerous van der Waals bonds between the H atoms of the alkane and basic oxygens of the zeolite are formed, when a hydrocarbon coordinates to Mg2+ ions. These intermolecular contacts significantly contribute to the overall adsorption energy, whereas they play only an indirect role in the adsorption of light alkanes on CaY. On the other hand, in the case of CaY the stabilization of alkanes in the electrostatic field of the partially shielded Ca2+ cation dominates the adsorption energy. It is concluded that the dominance of a particular type of intermolecular interactions is dependent on the properties of the adsorption site. The type of intermolecular interactions determines the final conformation of light alkanes adsorbed to the cation-exchanged zeolite Y. From the results in Chapters 2 – 4 an interesting effect is noted: although the smaller exchangeable cations are expected to bind molecules stronger and exhibit higher reactivity as compared to their larger counterparts because of the increased hardness of such cations, the calculations indicate that the properties of the metal ions stabilized in the zeolite matrix do not follow these trends. Indeed, when stabilized at zeolitic cation site, the larger ions are significantly coordinatively unsaturated. This leads to an enhancement of the adsorption properties of the larger cations in spite of their expected lower Lewis acidity. Molecular and dissociative adsorption of light alkanes on the more reactive high-silica zeolite ZSM-5 modified with zinc and cadmium is investigated in Chapter 5. Adsorption of ethane on coordinatively unsaturated soft Lewis acid sites (Zn2+ and Cd2+) in ZSM-5 zeolite results in stronger changes of the geometry and charge parameters of the adsorbed molecules as compared to the case of adsorption on MgY and CaY. It is found that the degree of the effective shielding of the exchangeable cations by the surrounding oxygen ions is an important factor that influences the perturbations of molecularly adsorbed ethane. The C2H6 binding energy does not apparently depend on the type of the cation (Zn or Cd), whereas the nature of the charge compensation of the cations is important. On the other hand, heterolytic dissociative adsorption is mainly controlled by the basicity of the proton-accepting oxygen-site (O-site) and the steric properties of the dissociation products, which determine their stability. As a result, no apparent correlation between the perturbations of the adsorbed molecules and their heterolytic dissociation is observed. Chapters 6 to 8 report cluster DFT calculations of the various potential reaction paths of catalytic dehydrogenation of light alkanes over zinc- and gallium-exchanged high-silica zeolites. The mechanism of the catalytic reaction and the most probable active site are identified. In addition, an attempt is made to understand the factors, which determine the catalytic activity of different intrazeolite cationic species as well as the preference for a particular reaction path. The theoretical results form a basis for interpreting the experimental catalytic data. Catalytic dehydrogenation of ethane over various zinc species in Zn/ZSM-5 zeolite is investigated in Chapter 6. It is shown that isolated Zn2+ stabilized at the cation sites with distantly placed anionic [AlO2]– framework units are the most probable active species. A novel mechanism of ethane dehydrogenation is proposed. It involves decomposition of the products of dissociative ethane adsorption (Z–Zn2+-C2H5 –···H+Z–) via one-step desorption of ethylene and hydrogen. This path is strongly favored for the isolated Zn2+ sites as compared to the conventional mechanism involving consecutive desorption of the dehydrogenation products. Similar to the initial heterolytic C-H bond cleavage, the basicity of the O-sites is a determinative factor for the particular reaction mechanism. In the case of Ga-exchanged ZSM-5 zeolite (Chapter 7), univalent gallium cations are the most probable active sites for reduced catalysts. Hydrogenated extra-framework species decompose rapidly toward Ga+ cations during the catalytic reaction. Initial oxidative addition of C2H6 to Ga+, which has been observed experimentally before, is shown to proceed via an indirect route involving heterolytic C-H cleavage over the Lewis acid-base pair formed by the Ga+ cation and a framework oxygen anion. The direct route is strongly disfavored due to the electronic properties of univalent gallium. C2H4 and H2 desorption in one step closes the catalytic cycle. Although this reaction is reminiscent to that proposed for Zn/ZSM-5, it strongly differs in nature and is controlled by the properties of the Ga site. It has been observed experimentally that the catalytic activity of ZSM-5 zeolite predominantly containing Ga+ ions can be remarkably enhanced after selective oxidation with N2O. The higher activity of the resulting material has been attributed to formation of extra-framework GaO+ ions. However, a detailed investigation of various possible reaction paths over isolated gallyl ions in ZSM-5 zeolite (Chapter 8) shows that ethane interacts with these species stoichiometrically, because of the extremely low stability of these sites. Indeed, the unfavorable tridentate coordination of gallium along with the high basicity of the extra-framework terminal oxygen ion in GaO+ leads to a rapid heterolytic dissociation of C2H6 molecules. The resulting products are very stable, and the closure of the catalytic cycle is not likely to occur. It is concluded that the isolated gallyl ions cannot be considered as catalytically active sites for light alkane dehydrogenation. The very low stability of GaO+ species, on the other hand, can cause their oligomerization in the zeolite micropores, resulting in formation of various multinuclear cationic gallium-oxide clusters (Chapter 9). Periodic DFT calculations show that formation of cyclic Ga2O2 2+ dimers is strongly favored independently of the aluminum distribution in the high-silica zeolite. Moreover, oligomers with a higher degree of aggregation can be in principle formed in oxidized Ga-exchanged zeolites. The zeolite lattice plays the role of a chelating ligand which stabilizes the (GaO)n cationic cluster. Parallels between conventional coordination chemistry and chemistry of high-silica zeolites modified with gallium are drawn. It is shown that the location and stability of such cationic clusters is mainly controlled by the favorable geometrical environment of the Ga3+ ions, while the effect of the direct interaction with the framework anionic sites which compensates for the positive charge of the extra-framework species is less important. In spite of higher stability, binuclear sites are shown to be active for alkane activation. The lower basicity of the extra-framework oxygen ions provides a path for the closure of the catalytic cycle. However, these sites still tend to reduce upon light alkane dehydrogenation via water desorption, resulting in formation of less reactive reduced Ga-species. The mechanistic insight provided by the quantum-chemical calculations suggests that the reduction path can be suppressed by addition of water to the hydrocarbon feed. This would lead to an increased steady-state concentration of reactive oxygenated Ga-species in the catalyst. The experimental catalytic tests (Chapter 9) indeed show significant enhancement of the dehydrogenation activity of Ga+ sites in ZSM-5 upon water co-feeding. Continuous addition of water is required to maintain a high steady-state concentration of the reactive oxygenated extra-framework species in the zeolite and leads to high and stable activity of the catalyst. Thus, it is shown that the reactivity of low-silica zeolites modified with rather inert alkaline- and alkali-earth cations derives mainly from the properties of the confined space of the zeolite cages. The high density and the specific arrangement of the exchangeable cations in the microporous matrix lead to optimum configuration of the adsorbed reagents and consequently to their chemical activation. On the other hand, the active sites in highsilica zeolites modified with softer Zn, Cd, and Ga cations are rather local and usually directly involved in catalytic transformations of the reagents. The chemical reactivity of these system derives from the properties of the Lewis acid-base conjugate pair, which in turn are controlled by the topology of the zeolite cation site accommodating the extraframework species as well as by the type of charge compensation and the nature of the cation. Both the Lewis acidity of the extra-framework cationic species and the properties of the conjugate basic sites are important for their activity. An optimum must be found in the Lewis acid-base properties of the zeolite active site to achieve a high catalytic activity

Computational approach to chemical reactivity of metal organic frameworks of MOFs

This chapter presents an introductory overview of important theoretical concepts and practical tools essential for computational modeling of chemical reactivity of metal organic frameworks using quantum chemical calculations. Besides the description of the basic concepts underlying different quantum chemical methods and their applicability for modeling extended molecular systems, the power of state-of-the-art computational quantum chemical techniques is illustrated by relevant examples from recent studies

Activation of light alkanes over zinc species stabilized in ZSM-5 zeolite : a comprehensive DFT study

The mechanism of alkane dehydrogenation over Zn/ZSM-5 zeolite was studied by means of density functional theory using the cluster modeling approach. Three types of active sites were considered: Zn2+ ions stabilized in conventional ion-exchange sites (ZnZs), Zn2+ ions stabilized in cation sites with distantly placed aluminum ions (ZnZd), or as binuclear [ZnOZn]2+ cations (ZnOZn). A comparison of the computed energetics of various reaction paths for ethane indicates that the catalytic reaction proceeds most easily over the ZnZd sites. The enhanced Lewis acidity of these sites facilitates the subsequent heterolytic C-H bond cleavage. The most favorable proton-accepting sites are not those of the framework ring to which Zn2+ is attached, but O sites of a neighboring ring. Although the reactivity of isolated Zn2+ ions strongly depends on the distribution of framework aluminum in ZSM-5 zeolite, the adsorption of alkane molecules is only slightly influenced by this factor. After the heterolytic C-H bond cleavage step, the zinc-alkyl group and acidic proton recombine via a cyclic transition state resulting in a one-step formation of an alkene and H2. This process is both thermodynamically and kinetically preferred for isolated Zn2+ sites over the consecutive mechanism. The activation barrier for the one-step elimination reaction strongly depends on the relative position of the reacting zinc-alkyl and framework attached H+ ions. Despite initial heterolytic C-H bond dissociation being strongly favored on the [ZnOZn]2+ cations, the activation energy for the subsequent decomposition of the resulting products is high

Molecular recognition in cation exchanged zeolites

The concepts of confinement- and molecular recognition-driven chemical reactivity of cation-exchanged zeolites is illustrated by our recent results from periodic and cluster density functional theory (DFT) calculations. The reactivity of alkali-earth- and alkaline-exchanged low-silica zeolites for selective photo-oxidation of alkenes with molecular oxygen and for N2O4 disproportionation is shown to be mainly due to the specific arrangement and the size of the cations in the zeolite cage. An attempt is made to separate the effects of basicity of the framework, the Lewis acidity of the extra-framework cations and the electrostatic field in the zeolite cage as well as its geometrical properties for the respective reactions. The importance of the favorable adsorption fashion of the reagents controlled by noncovalent interactions with the microporous matrix is shown. The role of the weak interactions with the zeolite walls and the factors, which determine the preference for a particular adsorption mode, are discussed by the example of light alkanes adsorption to Mg- and Ca-exchanged faujasites. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 201