Synthesis and properties of some 4H-1, 3, 4 benzothiadiazines /|nby Darko J. Vukov. -- 260 St. Catharines, Ont. : [s. n.],

The work herein has been divided into five sections. In the first section, a new method of converting N-aroyl- hydrazines to hydrazidic halides is described. The second section deals with the products of reaction of hydrazidic halides with thioacetate ion in acetonitrile at room temperature. A number of new acetylthiohydrazides has been isolated together with corresponding hyclrazidic sulphides. Examination of x-ray data for bis-[~ -(2,6- dibromophenylhydrazono) - benZYl] sulphide revealpd the symmetrical structure as the most probable. In the third section, which consists of the three subsections, the synthesis of the 4H-l,3,4 benzothiadiazine ring system has been extended to 4H-l,3,4 benzothiadiazines with substituents in the 5 and 6-positions. Extension of synthesis also involves 4H-l,3,4 benzothiadiazines with mora than one substituent. Nuclear magnetic resonance spectra of 5 and 6 substituted 4H-l,3,4 benzothiadiazines have been ,. recorded. The section ends with a discussion of the mass spectra of some 4H-l.3,4 benzothiadiazines. In the fourth section, which is divided into two sub- -sections, preparation of 7-nitro substituted 4H-l,3,4 benzothiadiazine from N-thiobenzoyl hydrazine and2,4-dinitro -fluorobenzene is found to be satisfactory. Thiohydrazides react with acetic anhydride, in some cases, to give products identical with acetylthiohydrazides obtained from the hydrazidic halides with thioacetate ion at room temperature. In most of the cases thiohydrazides are found to give anomalous products on reaction with acetic anhydride and mechanisms for their formation are discussed. In the fifth section, which forms three subsections, the 4H-l,3,4 benzothiadiazine ring system with a halogen substituent in the 7-position undergoes electrophilic attack preferentially in 5-posi tion. \fuen the 5-posi tion is occupied by a halogen atom, electrophilic substitution occurs at the 7-position of 4H-l,3,4 benzothiadiazine ring system. Substitution at the 4-nitrogen atom in 4H w l,3,4 benzo- -thiadiazine is extremely slow, probably due to delocalisa- -tion of the nitrogen lone pair in the system. Oxidation of 4H-l,3,4 benzothiadiazines occurs at the sulphur atom under relatively mild conditions. t The Appendix deals with the reaction of N-benzoyl-N - -(2,5-dibromophenyl)hydrazine with p-nitrothiophenol~ The proposed p-nitrothiophenoxy - intermediate may undergo benzothiadiazine formation in a proton exchange system.

The role of water in determining structure and function of macromolecules and macromolecular assemblies /

The interaction of biological molecules with water is an important determinant of structural properties both in molecular assemblies, and in conformation of individual macromolecules. By observing the effects of manipulating the activity of water (which can be accomplished by limiting its concentration or by adding additional solutes, "osmotic stress"), one can learn something about intrinsic physical properties of biological molecules as well as measure an energetic contribution of closely associated water molecules to overall equilibria in biological reactions. Here two such studies are reported. The first of these examines several species of lysolipid which, while present in relatively low concentrations in biomembranes, have been shown to affect many cellular processes involving membrane-protein or membrane-membrane interactions. Monolayer elastic constants were determined by combining X-ray diffraction and the osmotic stress technique. Spontaneous radii of curvature of lysophosphatidylcholines were determined to be positive and in the range +30A to +70A, while lysophosphatidylethanolamines proved to be essentially flat. Neither lysolipid significantly affected the bending modulus of the monolayer in which it was incorporated. The second study examines the role of water in theprocess of polymerization of actin into filaments. Water activity was manipulated by adding osmolytes and the effect on the equilibrium dissociation constant (measured as the criticalmonomer concentration) was determined. As water activity was decreased, the critical concentration was reduced for Ca-actin but not for Mg-actin, suggesting that 10-12 fewer water molecules are associated with Ca-actin in the polymerized state. Thisunexpectedly small amount of water is discussed in the context of the common structural motif of a nucleotide binding cleft.

Synthesis, Characterisation and Properties of (Ba1-xSrx) (Nd1/2Nb1/2 ) 03 Ceramics for Application as Dielectric Resonators in Microwave Circuits

The (Ba1-x Srx) (Nd1/2, Nb1/2) O3 ceramics have been prepared by the conventional ceramic route for different values of x. Addition of a small amount of CeO2(1 wt%) as a sintering aid increased the density of the samples. The structure and microstructure of the sintered samples are studied by X-ray diffraction and SEM methods. The dielectric properties of the samples are measured in the microwave frequency region as a function of composition. The dielectric constant decreases as x increases. The coefficient of thermal variation of resonant frequency decreases as the Sr content increases and goes to the negative side. The dielectric properties of (Ba1-x Srx) (Nd1/2, Nb1/2) O3 are in the range suitable for application as dielectric resonators in microwave circuits

Synthesis, Characterization and Properties of Ca5A2TiO12 (A=Nb, Ta) Ceramic Dielectric Materials for Applications in Microwave Telecommunication Systems

Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Q5 x f > 30000GHz) and small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator applications in microwave integrated circuits. [DOI: 10. 1 143/JJAP.41.3834]

Structure and energetics of mixed 4He-3He drops

Using a finite-range density functional, we have investigated the energetics and structural features of mixed helium clusters. The possibility of doping the cluster with a molecule of sulfur hexafluoride is also considered. It is seen that the repulsion introduced by the impurity strongly modifies the properties of the smallest drops. Although only a qualitative comparison is possible, the gross features displayed by our calculations are in agreement with recent experimental findings.

Structure and far-infrared edge modes of quantum antidots at zero magnetic field

We have investigated edge modes of different multipolarity sustained by quantum antidots at zero magnetic field. The ground state of the antidot is described within a local-density-functional formalism. Two sum rules, which are exact within this formalism, have been derived and used to evaluate the energy of edge collective modes as a function of the surface density and the size of the antidot.

Electronic structure and magnetic interactions of the spin-chain compounds Ca2CuO3 and Sr2CuO3

The results are presented of a combined periodic and cluster model approach to the electronic structure and magnetic interactions in the spin-chain compounds Ca2CuO3 and Sr2CuO3. An extended t-J model is presented that includes in-chain and interchain hopping and magnetic interaction processes with parameters extracted from ab initio calculations. For both compounds, the in-chain magnetic interaction is found to be around -240 meV, larger than in any of the other cuprates reported in the literature. The interchain magnetic coupling is found to be weakly antiferromagnetic, -1 meV. The effective in-chain hopping parameters are estimated to be ~650 meV for both compounds, whereas the value of the interchain hopping parameter is 30 meV for Sr2CuO3 and 40 meV for Ca2CuO3, in line with the larger interchain distance in the former compound. These effective parameters are shown to be consistent with expressions recently suggested for the Néel temperature and the magnetic moments, and with relations that emerge from the t-J model Hamiltonian. Next, we investigate the physical nature of the band gap. Periodic calculations indicate that an interpretation in terms of a charge-transfer insulator is the most appropriate one, in contrast to the suggestion of a covalent correlated insulator recently reported in the literature.

Investigations On The Preparation And Properties Of Reactively Evaporated Lead Sulphide And Tin Telluride Thin Films

The work reported in this thesis is the preparation, and the structural, electrical and optical properties of reactively evaporated lead sulphide and tin telluride thin films. The three temperature method had been used for the preparation of these semiconductor thin films. In this preparation technique constituent elements are evaporated from separate sources with the substrate kept at a particular temperature. when one of the constituent element is a gas near room temperature, the method is often called reactive evaporation. It has been found for many materials that a stoichiometric interval exists with a limited range of flux and substrate temperature. Usually this technique is used for the preparation of thin films of high melting point compounds or of materials which decompose during evaporation. Tin telluride and lead sulphide are neither high melting point materials nor do they decompose on melting. But even than reactive evaporation offers the possibility of changing the ratios of the flux of the constituent elements within a wide range and studying its effect on the properties of the films

An investigation on the preparation and properties of some transparent conducting oxides and lead selenide thin films”

The investigation of physical properties of matter has progressed so much during the last hundred years. Today physics is divided in to a large distinct group of special branches. These branches are distinguished by the particular area studied, method of investigation and so on. An independent and important branch that has developed is the physics ofthin films.Any object in solid or liquid form with one of its dimensions very much smaller than that of the other two may be called a thin film. It is having only one common property, namely, one of their dimensions is very small, though all their physical properties may be different. Thin layers of oil, floating on the surface of water, with their fascinating colours, have attracted men’s curiosity from time immemorial. The earliest application of thin films was the protective coatings in the form of paints. A thin layer of tin has been used from ancient times to protect copper utensils from corrosion. Indium thin films are used in certain applications on account of their good lubricating property. Relay contacts are coated with thin films of rare earth metals in order to prevent burning due to arcing. Hard coatings are also available using diamond like carbon (i-carbon). The basic properties of thin films are of considerable interest because of their potential applications in various fields of science and technology

Theoretical study of magnetism, structure and chemical order in transition-metal alloy clusters

Research on transition-metal nanoalloy clusters composed of a few atoms is fascinating by their unusual properties due to the interplay among the structure, chemical order and magnetism. Such nanoalloy clusters, can be used to construct nanometer devices for technological applications by manipulating their remarkable magnetic, chemical and optical properties. Determining the nanoscopic features exhibited by the magnetic alloy clusters signifies the need for a systematic global and local exploration of their potential-energy surface in order to identify all the relevant energetically low-lying magnetic isomers. In this thesis the sampling of the potential-energy surface has been performed by employing the state-of-the-art spin-polarized density-functional theory in combination with graph theory and the basin-hopping global optimization techniques. This combination is vital for a quantitative analysis of the quantum mechanical energetics. The first approach, i.e., spin-polarized density-functional theory together with the graph theory method, is applied to study the Fe$_m$Rh$_n$ and Co$_m$Pd$_n$ clusters having $N = m+n \leq 8$ atoms. We carried out a thorough and systematic sampling of the potential-energy surface by taking into account all possible initial cluster topologies, all different distributions of the two kinds of atoms within the cluster, the entire concentration range between the pure limits, and different initial magnetic configurations such as ferro- and anti-ferromagnetic coupling. The remarkable magnetic properties shown by FeRh and CoPd nanoclusters are attributed to the extremely reduced coordination number together with the charge transfer from 3$d$ to 4$d$ elements. The second approach, i.e., spin-polarized density-functional theory together with the basin-hopping method is applied to study the small Fe$_6$, Fe$_3$Rh$_3$ and Rh$_6$ and the larger Fe$_{13}$, Fe$_6$Rh$_7$ and Rh$_{13}$ clusters as illustrative benchmark systems. This method is able to identify the true ground-state structures of Fe$_6$ and Fe$_3$Rh$_3$ which were not obtained by using the first approach. However, both approaches predict a similar cluster for the ground-state of Rh$_6$. Moreover, the computational time taken by this approach is found to be significantly lower than the first approach. The ground-state structure of Fe$_{13}$ cluster is found to be an icosahedral structure, whereas Rh$_{13}$ and Fe$_6$Rh$_7$ isomers relax into cage-like and layered-like structures, respectively. All the clusters display a remarkable variety of structural and magnetic behaviors. It is observed that the isomers having similar shape with small distortion with respect to each other can exhibit quite different magnetic moments. This has been interpreted as a probable artifact of spin-rotational symmetry breaking introduced by the spin-polarized GGA. The possibility of combining the spin-polarized density-functional theory with some other global optimization techniques such as minima-hopping method could be the next step in this direction. This combination is expected to be an ideal sampling approach having the advantage of avoiding efficiently the search over irrelevant regions of the potential energy surface.

Synthesis, structure and reactivity of novel CuI, CuII and CuIII complexes containing triaza and hexaaza macrocyclic ligands

El treball de tesi s'emmarca dins del camp de la bioinorgànica, disciplina que estudia les propietats estructurals i de reactivitat dels centres actius dels enzims, servint-se de models síntètics de baix pes molecular per tal d'intentar reproduïr la reactivitat presentada per l'enzim i conèixer els mecanismes de reacció a nivell molecular que tenen lloc en els processos biològics.1 Més concretament el treball posa especial èmfasi en els processos d'activació d'oxigen molecular que tenen lloc en les metaloproteïnes de Coure del Tipus 3, com són l'hemocianina i la tirosinasa, ambdues presentant un complex dinuclear de Cu(I)) en el centre actiu de la forma reduïda, capaç d'activar l'O2 cap a espècies de tipus peròxid.2 Un altre camp d'interès ha estat l'estudi dels processos d'activació d'enllaços C-H no activats en hidrocarburs, tant per la seva importàcia a nivell industrial com per comprendre els mecanismes intrínsecs d'aquesta activació a través de metalls de trancisió.3,4 Durant el treball de tesi presentat s'ha desenvolupat la síntesi de nous complexes de Coure(I), Coure(II) y Cu(III) utilitzant lligands macrocíclics de tipus triaza i hexaaza, i s'han estudiat la seves propietats estructurals així com la seva reactivitat. La reacció dels lligands triazacíclics H32m, H2Me33m i H33m amb sals de coure(II) dóna lloc a una reacció de desproporció de Cu(II) per obtenir-se en quantitats equimolars un complex organometàl·lic de Cu(III) i un complex de Cu(I). La caracterizació estructural exhaustiva dels complexes del tipus aryl-Cu(III) evidencia la formació d'un enllaç organometàl·lic entre l'àtom de Cu(III) i el carboni més próxim de l'anell aromàtic del lligand. Aquesta reacció, a més de representar una nova forma de desproporció en la química del Cu, suposa l'activació d'un enllaç C-H aromàtic a temperatura ambient que, mitjançant l'estudi cinètic d'aquesta desproporció per espectroscòpia UV-Vis, dels càlcul de l'efecte cinètic isotòpic utilitzant el lligand deuterat en el C-H de l'anell, juntament amb el recolzament teòrics dels càlculs DFT per a la optimització de geometries d'intermedis de reacció, ens permeten proposar un mecanisme de reacció pel nostre sistema, on l'activació de l'enllaç C-H aromàtic transcorre per la formació d'un enllaç de tipus agòstic C-H ? Cu(II),5 seguit de la desprotonació del C-H aromàtic per acció d'una base i posterior transferència electrònica per obtenir el complex organometàlic de Cu(III) i el complex de de Cu(I). En quant a la reactivitat d'aquests complexes organometàl·lics aryl-Cu(III) s'ha observat que una base en medi aquós causa la inestabilitat d'aquests compostos, evolucionant cap a la inserció d'un àtom d'oxigen sobre la posició activada de l'anell aromàtic, per a donar lloc a un complex dinuclear de Cu(II) amb dos grups fenoxo actuant de pont entre els àtoms metàl·lics. La reacció transcorre per un intermedi colorejat, caracteritzat com el complex ayl-Cu(III) monodesprotonat en una de les seves amines benzíliques, els quals s'observen igualment en la reacció dels correponents complexos de Cu(I) amb oxigen molecular (O2). És en els nostres sistemes en els quals es descriu per primera vegada la participació d'intermedis organometàl·lics Cu(III)-C en processos d'hidroxilació aromàtica, tals com el desenvolupat per l'enzim tirosinasa o per alguns dels seus models químics de síntesi.6,7,8 S'han estudiat les propietats magnètiques dels quatre bis(fenoxo)complexes de Cu(II) descrits, obtenint-se uns acoplaments de tipus antiferromagnètic o ferromagnètic de diversa magnitud, depenent del solapament orbitalari a l'enllaç Cu-O, a través del qual es produeix el superintercanvi. Nous complexos de Cu(I) sintetitzats amb lligands hexaazamacrocíclics han estat estudiats, i posant especial èmfasi a la seva reactivitat respecta a l'activació d'oxigen molecular (O2). S'ha observat una reactivitat diferenciada segons la concentració de complex de Cu(I) utilitzada, de manera que a altes concentracions s'obté un carbonato complex tetranuclear de Cu(II) per fixació de CO2 atmosfèric, mentre que a baixes concentracions s'observa la hidroxilació aromàtica intramolecular d'un dels anells benzílics del lligand, reacció que presumiblement transcorre per atac electrofílic d'un peroxo complex intermedi sobre el sistema ? de l'anell.6 Els resultats obtinguts en aquest treball ens mostren la facilitat per activar enllaços C-H aromàtics per metalls de transició de la primera sèrie (Cu, Ni) quan aquests estan suficientment pròxims a l'enllaç C-H, en unes condicions de reacció molt suaus (1atm., temperatura ambient). Els nous complexos organometàl·lics Aryl-Cu(III) són el producte d'una nova reacció de desproporció de Cu(II), així com un posició aromàtica activada que podria ser el punt de partida per l'estudi de funcionalització selectiva d'aquests grups aromàtics.

Hydrogen-bonded interpolymer complexes. Formation, structure and applications

Noncovalent interactions play key roles in many natural processes leading to the self-assembly of molecules with the formation of supramolecular structures. One of the most important forces responsible for self-assembly is hydrogen bonding, which also plays an important role in the self-assembly of synthetic polymers in aqueous solutions. Proton-accepting polymers can associate with proton-donating polymers via hydrogen bonding in aqueous solutions and form polymer-polymer or interpolymer complexes. There has been an increased interest among researchers in hydrogen-bonded interpolymer complexes since the first pioneering papers were published in the early 1960s. Several hundred research papers have been published on various aspects of complex formation reactions in solutions and interfaces, properties of interpolymer complexes and their potential applications. This book focuses on the latest developments in the area of interpolymer complexation via hydrogen bonding. It represents a collection of original and review articles written by recognized experts from Germany, Greece, Kazakhstan, Poland, Romania, Russia, UK, Ukraine, and the USA. It highlights many important applications of interpolymer complexes, including the stabilization of colloidal systems, pharmaceuticals, and nanomaterials.