ABSTRACT AXIAL LIGAND SUBSTITUTION REACTION KINETICS OF PYRIMIDINE-2-THIONATO BRIDGED BINUCLEAR PLATINUM(III) COMPLEXES G&ouml / y, Aytun&ccedil / M. S. Department of Chemistry Supervisor: Prof. Dr. H&uuml / seyin iS&ccedil / i Co-supervisor: Assoc. Prof.Dr. Seniz &Ouml / zalp Yaman September 2007, 89 pages The kinetics of the ligand substitution reactions, which is represented by the equation, [Pt2(C4H3N2S)4X2] + 2Y- Pt2(C4H3N2S)4Y2 + 2X- where X- = Cl-, Br-, I- and Y- = Cl-, Br-, I- are studied in acetonitrile in the presence of excess Y- ion concentrations, under constant ionic strength. All reactions are reversible. The rate of the above reaction is dependent on binuclear complex and entering ligand concentrations. Thus general rate equation can be written as Rate = k [Y-]a[Pt2(C4H3N2S)4X2]b The reaction rates are first order with respect to the substrate complex (b=1). The experimentally determined values of the order of the reaction with repect to entering ligand, &ldquo / a&rdquo / , are 0.96&plusmn / 0.057 (X=I-, Y=Cl-), -0.49&plusmn / 0.037 (X=Cl-, Y=I-), 0.28&plusmn / 0.023 (X=I-, Y=Br-), 0.48&plusmn / 0.044 (X=Br-, Y=I-), 0.53&plusmn / 0.042 (X=Br-, Y=Cl-), and -0.21&plusmn / 0.014 (X=Cl-, Y=Br-). The rate constants are 12.1&plusmn / 2.05 M-1s-1 (X=I-, Y=Cl-), (5.7&plusmn / 1.6)x10-3 M1/2s-1 (X=Cl-, Y=I-), 0.3&plusmn / 0.27 M-0.3s-1 (X=I-, Y=Br-), 0.53&plusmn / 0.11 M-1/2s-1 (X=Br-, Y=I-), 1.74&plusmn / 0.16 M-1/2s-1 (X=Br-, Y=Cl-), and 1.71&plusmn / 0.37x10-2 M0.2s-1 (X=Cl-, Y=Br-). To obtain information about the energetics of the reactions, the temperature dependence of the rate constants is determined and the activation parameters &amp / #916 / H* and &amp / #916 / S* are calculated. The values &amp / #916 / S* are negative and, in the range of -81 and -236 J K-1 mol-1. These results support an associative-interchange, Ia, mechanism. All data obtained in this work are used to propose a mechanism which will be consistent with the experimentally determined rate law.

In this work , metal functional polymers, namely Cr-PS-b-P2VP, Co-PS-b-P2VP, Au-PS-b-P2VP, Fe-PS-b-P2VP and Mo-PS-b-P2VP were prepared by thermal reaction of hexacarbonylchromium, Cr(CO)6, octacarbonyldicobalt,Co2(CO)8, hydrogentetrachloroaurate(III), H(AuCl4).4H2O, trichloroiron(III), FeCl3.6H2O, molybdenum(VI)oxide, MoO3 and PS-b-P2VP. TEM images indicated formation of AuIII, Cr and Co nanoparticles. On the other hand, crystalline structures were detected for Fe-PS-b-P2VP and Mo-PS-b-P2VP. Samples involving nanoparticles were further characterized by FTIR, UV-Vis and direct pyrolysis mass spectroscopy techniques. FTIR analysis indicated dissapearance of characteristic carbonyl peaks of Cr(CO)6 and Co2(CO)8 for Cr-PS-b-P2VP and Co-PS-b-P2VP samples. The appearance of a peak at about 467 cm-1 supported the formation of metal-nitrogen bond. Pyrolysis mass spectrometry analysis showed an increase in the thermal stability of P2VP chains involving coordinated pyridine units. The thermal stability of these chains increased in the order Co&lt / Cr &lt / Au3+ indicating stronger coordination in the same order.

Zeolites are microporous hydrated aluminosilicate crystals containing alkali and/or alkali earth metal cations in their frameworks. Due to their molecular size pores, they can separate molecules according to their size and shape. Zeolites are mostly used in ion exchange, adsorption processes and catalytic applications. The hydrophilic/hydrophobic character of zeolites also makes them favorable materials for adsorption based separations. Recently the potential of zeolite/ceramic composite membranes have been shown in the separation of liquid and gas mixtures. Self-supported zeolite membranes with asymmetric structure can be an alternative to the composite zeolite membranes. Because asymmetric structure may eliminate the problems originated from the differences in thermal expansion coefficients of zeolites and ceramics. In this study tubular zeolite A membranes were prepared on binderless zeolite A supports. The supports were perepared by hydrothermal conversion of amorphous aluminosilicate tubes into zeolite A. The amorphous aluminosilicate powder, which was obtained by filtering the homogenous hydrogel with a composition of 2.5Na2O:1Al2O3:1.7SiO2:150H2O, was mixed with an organic binder (HEC-Hydroxyethyl Cellulose) and water to obtain the paste. The paste was then extruded through a home-made extruder into bars and tubes. These extrudates were dried at room temperature for 24 hours, calcined at 600oC for 2 hours to remove organic binder and finally synthesized at 80oC for 72 hours in hydrothermal conditions to convert amorphous aluminosilicate to zeolite. The effect of composition of the synthesis solution on the crystallinity and morphology of zeolite A tubes and bars were investigated. The crystallization field of zeolite A bars has been established and shown on a ternary phase diagram. Tubes were mechanically stable, typically had a crystallinity over 90% and a macroporosity of 35%. The tubes were composed of highly intergrown crystals of zeolite A. The average particle size was 3.5 &micro / m. The asymmetric membranes were synthesized by growing zeolite A films on binderless zeolite A supports with a geometry of disk, bar and tube. Continuous zeolite A films can only be obtained when the supports were saturated with water prior to synthesis. The film thicknesses were approximately 5 &micro / m on disks and approximately 10 &micro / m on tubes. A method was proposed to prepare self-supported tubular zeolite A membranes in this study.

Zirconium tungstate (ZrW2O8) is a ceramic that shows large isotropic negative thermal expansion over a wide range of temperature. This unique property makes it an interesting candidate for applications where thermal expansion mismatch between components constitutes a problem. ZrW2O8 is typically produced by solid-state reaction between zirconium oxide and tungsten oxide at 1200oC. In some studies, ZrW2O8 precursors have been produced from relatively expensive zirconium and tungsten sources. While the origin of negative thermal expansion has been the main focus in the majority of publications, production of particles with controlled size, distribution and morphology has not been studied extensively. Electrospinning is a simple technique for producing micron/nano sized fibers from polymer solutions. The method can also be used for producing ceramic or polymer/ceramic composite fibers by electrospinning of a mixture of ceramic precursors or ceramic nanoparticles with suitable polymers. Ceramic precursors could be synthesized either by sol-gel or chemical precipitation routes before mixing them with polymer solutions and a final burnout step would be needed, in case the fiber is desired to be composed of the ceramic phase. Electrospinning technique has not been employed to the production of ZrW2O8 ceramic fibers. In this study a novel precursor for ZrW2O8 from relatively cheaper and abundant starting chemicals, namely zirconium acetate and tungstic acid were used. Experimental details of development of the precursor are presented with a discussion on the effects of solution parameters on the phase purity of the fired product. Besides the solution parameters investigated (i.e. solubility of tungstic acid, adjustment of the stoichiometry, final pH of the solution, ageing time), evolution of the heat treatment protocol was used in the production of phase pure ZrW2O8. Second, the suitability of the developed precursor for producing ZrW2O8 in fiber form was investigated. Preliminary studies involved the adjustment of the viscosity of precursor solution for electrospinning with poly (vinyl alcohol) (PVA). Optimum PVA concentration leading to bead-free nanofiber mats and a method to increase the fiber production rate were reported. The characterization of the products was achieved by SEM and XRD.

Lithium tetraborate (Li2B4O7) has aroused interest of scientists since 1960s by the courtesy of the thermoluminescence (TL) property it possesses. Over and above, it found widespread use in surface acoustic wave apparatuses, in sensor sector and in laser technology due to its non linear optical characteristics. For the uses in thermoluminescence dosimetry lithium tetraborate is activated by addition of a variety of metals as dopants. This study comprises the synthesis of lithium tetraborate by two methods (high temperature solid state synthesis and water/solution assisted synthesis) as well as doping and characterization of the material. Lithium tetraborate is readily commercially available in TL dosimetry / hence, the main aim is to specify practical production conditions to pioneer domestic production. In high temperature synthesis, the initial heating was performed at 400oC for 3 hours. Then the samples were heated at 750oC for two hours, intermittently mixed to enhance diffusion and exposed to the same temperature for another two hours. In water/solution assisted synthesis, stoichiometric quantities of reactants were mixed in water by heating and agitating in order to achieve homogenous mixing and good dispersion of the material. The remnant of water was removed from the system by 3 hours initial heating at 150oC. The synthesis stage is followed by doping step where the metals Cu, Ag and In in different proportions were doped in lithium tetraborate by solid state and solution assisted synthesis techniques. Powder X-ray diffraction method was employed for the characterization of the material. The thermal properties of doped and un-doped materials were studied by DTA (Differential Thermal Analyses). Besides, FT-IR (Fourier Transform Infra red) spectrometry analyses were performed in order to detect differences in the bond structure caused by doping The XRD patterns obtained showed that lithium tetraborate production was successful by both high temperature solid state synthesis and solution assisted synthesis Moreover, it was inferred from the XRD results that addition of dopants did not have a sound effect on the crystal structure. Furthermore, the DTA results displayed that addition of different dopants to the structure of lithium tetraborate did not cause any noticeable difference. The extensive TL measurements showed that the TL response of the material produced is affected by production and doping methods.

In this study, differences in glow curves of Mn doped LTB powder samples synthesized with solid and wet synthesis methods and doped by using solid and wet doping techniques were investigated. Firstly, LTB was synthesized by using wet synthesis method which mainly comprises dissolution of reactants in water as solvent. Second way to produce LTB which was used in this study was solid synthesis method. In solid synthesis method, reactants were mixed in powder form. In the second part of the study, LTB produced by two different methods were doped with Mn and additionally Ag, Mg or P by using two different doping techniques. In order to see structural differences between differently synthesized and differently doped LTB samples which contained different amount of dopant powder X-Ray Diffraction (XRD) method was employed. Besides, FTIR (Fourier Transform Infrared) spectroscopy analyses were performed in order to detect differences in the bond structure caused by doping. Additionally, Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES) was used to determine the actual amount of dopant in LTB. Also morphological structures of samples were compared by using Scanning Electron Microscopy (SEM). Thermoluminescence measurements were performed with (TLD) Thermoluminescence Dosimeter equipment. XRD and FTIR analysis showed that syntheses of products were done in well success. Addition of dopants did not cause any changes in structural or bonding properties of LTB. It was possible to observe that, synthesis and doping methods and dopant concentration effect the thermoluminescence glow curves of doped LTB.

Recently, the use of block copolymers in preparation of nanocomposites has received great attention as they form well-defined micelles. In this work, the synthesis of different metal functional copolymers, nano structural metal composites and investigation of their reaction mechanism and thermal characteristics by pyrolysis mass spectroscopy have been aimed. Namely, polyisoprene-block-poly2vinylpyridine, (PI-b-P2VP) and poly2vinylpyridine-block-polymetylmethacrylate, (PMMA-b-P2VP) were used as block copolymers and the thermal reaction of these copolymers with two different transition metal complexes Cr(CO)6 and HAuCl4.3H2O were investigated which mostly lead to the coordination of metal through nitrogen atom of the pyridine ring which then degrates to form nano particles. The samples were further characterized by TEM, ATR-FT-IR, UV-Vis and Direct-Pyrolysis Mass Spectroscopy techniques. TEM images proved the formation of nanoparticles and the results showed that synthesized Au nanoparticles have 2 to 3 fold larger size than Cr nanoparticles. ATR-FT-IR spectrum of metal functional copolymers showed that the disappearance of characteristic peaks of pyridine stretching and bending mode when metal coordinates to the pyridine nitrogen. Furthermore, the spectrum indicated the appearance of a new absorption peak at around 740 cm-1 which may be a clue for the coordination of gold(III) ion to the pyridine nitrogen. Different from chromium case, in the spectrum of Au3+-(PMMA-b-P2VP), CO stretching frequency of PMMA which may appear at around 1720&ndash / 1718 cm-1 decreased in intensity while a new absorption peak appeared at around 1600 cm-1. This results reveals that electron deficient gold (III) ion prefers the coordination from both donor atoms namely carbonyl oxygen PMMA and pyridine nitrogen of P2VP in order to compensate its electron deficiency. In the UV-Vis spectrum of copolymers, Cr-functional copolymers showed a sharp absorption peak appeared at around 290 nm is attributed to a MLCT transition from chromium atom to * orbital of pyridine group. Furthermore, Au-functional copolymers showed a completely new absorption band at around 320 nm which can be associated again with a LMCT transition since gold is electron deficient and more willing to accept electrons from the ligand. Pyrolysis mass spectrometry analysis showed that poly2vinylpyridine blocks for each copolymers were affected similarly but polyisoprene block was not affected much from the coordination of metal compared to poly(methyl methacrylate) block in copolymers. For (PI-b-P2VP), Au3+ coordination to copolymer resulted in the higher thermal stability compared to Cr coordination. For (PMMA-b-P2VP), different from Cr, Au3+ coordination to P2VP nitrogen atom was extensive and PMMA based products changed drastically due to the coordination of electron deficient Au3+ to PMMA carbonyl group.

The use of microporous materials with ordered porous structures as the hosts to stabilize metal nanoclusters has attracted particular interest in the catalysis because the pore size restriction could confine the growth of nanoclusters and lead to an increase in the percentage of catalytically active surface atoms. In this dissertation we report the preparation, characterization and the investigation of the catalytic performance of zeolite framework stabilized ruthenium(0) nanoclusters in the hydrolysis of sodium borohydride and the hydrogenation of aromatics. The zeolite framework stabilized ruthenium(0) nanoclusters were prepared by borohydride reduction of ruthenium(III)-exchanged zeolite-Y in aqueous solution at room temperature and isolated as black powders. Their characterization by using ICP-OES, XRD, TEM, ZC-TEM, HR-TEM, TEM-EDX, SEM, XPS, DR-UV-vis, far-IR, mid-IR, Raman spectroscopy, N2 adsorption-desorption technique and (P(C6H11)3)/(PC6H11O3) poisoning experiments reveal the formation of ruthenium(0) nanoclusters within the zeolite cages as well as on the external surface of zeolite without causing alteration in the framework lattice or loss in the crystallinity. The catalytic performance of zeolite framework stabilized ruthenium(0) nanoclusters depending on the various parameters was tested in the hydrolysis of sodium borohydride and the hydrogenation of aromatics. The important results obtained from these experiments can be listed as follows: (i) the zeolite framework stabilized ruthenium(0) nanoclusters provide a record total turnover number (103200 mol H2/mol Ru) and turnover frequency (33000 mol H2/mol Ru&bull / h) in the hydrolysis of sodium borohydride at room temperature, (ii) they also catalyze the same reaction in the basic medium (in 5 wt % NaOH solution) at room temperature with the unprecedented catalytic activity (4000 mol H2/mol Ru&bull / h) and lifetime (27200 mol H2/mol Ru), (iii) the isolated and vacuum dried samples of zeolite framework stabilized ruthenium(0) nanoclusters are active catalysts in the hydrogenation of cyclohexene, benzene, toluene and o-xylene in cyclohexane, they provide TOF values of 6150, 5660, 3200, and 1550 mol H2/mol Ru&bull / h, respectively under mild conditions (at 22.0 &plusmn / 0.1 &deg / C, and 40 &plusmn / 1 psig of initial H2 pressure), (iv) more importantly, the zeolite framework stabilized ruthenium(0) nanoclusters are the lowest temperature, most active, most selective (100 % selectivity with complete conversion) and longest lifetime catalyst hitherto known for the hydrogenation of benzene to cyclohexane in the solvent-free system (TTON of 2420 and TOF of 1040 mol benzene/mol Ru&bull / h) under mild conditions (at 22.0 &plusmn / 0.1 &deg / C, and 40 &plusmn / 1 psig of initial H2 pressure), (v) moreover, the resultant ruthenium(0) nanoclusters exhibit high durability throughout their catalytic use against agglomeration and leaching. This significant property makes them reusable catalyst without appreciable loss of their inherent activity.

Among the new hydrogen storage materials, ammonia borane (AB) appears to be the most promising one as it has high hydrogen content, high stability, and being environmentally benign. Dehydrogenation of AB can be achieved via hydrolysis, thermolysis or methanolysis. Methanolysis of AB eliminates some drawbacks of other dehydrogenation reactions of AB. The use of colloidal and supported particles as more active catalyst than their bulky counterparts for the hydrolysis of AB implies that reducing the particle size can cause an increase in the catalytic activity as the fraction of the surface atoms increases by decreasing the particle size. Similarly, transition metal nanoclusters can be utilized as catalyst for the methanolysis of AB as well. For this purpose transition metal nanoclusters need to be stabilized to a certain extent. Actually in the catalytic application of transition metal nanoclusters one of the most important problems is the aggregation of nanoclusters into bulk metal, despite of using the best stabilizers. In this regards, the use of metal nanoclusters as catalysts in systems with confined void spaces such as inside mesoporous and microporous solids appears to be an efficient way of preventing aggregation. In this dissertation we report for the first time the use of intrazeolite rhodium(0) nanoclusters as a catalyst in the methanolysis of ammonia borane. Rhodium(0) nanoclusters could be generated in zeolite-Y by a two-step procedure: (i) incorporation of rhodium(III) cations into the zeolite-Y by ion-exchange, (ii) reduction of rhodium(III) ions within the zeolite cages by sodium borohydride in aqueous solution, followed by filtration and dehydration by heating to 550 &deg / C under 10-4 Torr. Zeolite confined rhodium(0) nanoclusters are stable enough to be isolated as solid materials and characterized by ICP-OES, XRD, SEM, EDX, HRTEM, XPS and N2 adsorption-desorption technique. The zeolite confined rhodium(0) nanoclusters are isolable, bottleable, redispersible and reusable. They are active catalyst in the methanolysis of ammonia-borane even at low temperatures. They provide exceptional catalytic activity with an average value of TOF = 380 h-1 and unprecedented lifetime with 74300 turnovers in the methanolysis of ammonia-borane at 25 &plusmn / 0.1 &deg / C. The work reported here also includes the full experimental details of previously unavailable kinetic data to determine the rate law, and activation parameters (Ea, &amp / #916 / H&amp / #8800 / and &amp / #916 / S&amp / #8800 / ) for the catalytic methanolysis of ammonia-borane.

This thesis analyzes the coming out action of individuals through perception of political identity. Instead of considering coming out as an individual experience, it is discussed as a political action that effects the others around the individual. This political action is examined from the Queer Theory&rsquo / s perspective of subverting the gender norms. The coming out experience of lesbians, gays and bisexuals not only has an impact of their personal environment, but also effects their relation to the LGBT movement. The importance of coming out in LGBT movement is explained through the interviews with lesbians, gays and bisexuals. Where they place themselves politically in their socialization process is analyzed. LGBT movement&rsquo / s historical background is introduced and compared with the movement in Turkey. The issues originate from Turkish society&rsquo / s social structure is indicated through interviews.