The synthesis of nanomaterials has received considerable attention in the past few decades owing to the enhanced physical and chemical properties of the particles upon approaching dimensions on the order of the Bohr radius. Several routes have been established for the synthesis of colloidal nanoparticles, where selection of reducing agent and stabilizer along with manipulation of reaction conditions dictate the outcome of the synthetic efficacy. In this work, a number of tactics have been examined in the synthesis of gold nanoparticles, which as a whole can serve as a guideline for the photochemical preparation of various aqueous metal colloids. Aqueous gold nanoparticles have been synthesized with a variety of photoinitiators such as alpha-hydroxy ketones and alpha-amino ketones through the unimolecular photorelease of free radicals with reducing character. A water-soluble benzoin operated as an excellent precursor and subsequent stabilizer of colloidal gold by its photoproducts. A second technique has operated via an intermolecular pathway for the generation of reducing ketyl radicals from hydrogen atom abstraction involving aromatic ketones with a number of hydrogen donors. Selecting ketones with low-lying triplet states and reactive hydrogen donors led to the facile formation of AuNP in micellar media. Other syntheses of gold nanoparticles have focused on the reactivity of the metal salt itself, such that photolysis of the coordination complex in the vicinity of hydrogen donors has also resulted in efficient gold nanoparticle synthesis. These approaches have been optimized by manipulation of reagent concentrations and photolysis conditions to yield stable colloids with control over particle diameter as well as morphology. With these strategies in place, the growth of nanoparticles and their surface reactivity were investigated through various methods. In particular, seed-mediated growth and kinetics were established to resolve an autocatalytic mechanism for particle formation. In addition, a novel photochemical seed-mediated growth technique was established for size selective synthesis. Gold nanoparticles were also derivatized with a series of functional groups to evaluate ligand-nanoparticle interactions, leading the way to possible applications for the materials as optical sensors. Additionally, the photo-releasing synthetic approach has been applied to the design of gold on inorganic supports for heterogeneous catalysis, where preliminary research has revealed their catalytic activity.

$\rm \{\lbrack (TMS)NCH\sb2CH\sb2\rbrack\sb2N(TMS)\}\sb2V\sb2(\mu$-Cl)$\sb2$ was prepared by reaction of $\rm VCl\sb3(THF)\sb3$ with the corresponding amide, and then reacted with sulfur to yield what it is thought to be $\rm\{\lbrack (TMS)NCH\sb2CH\sb2\rbrack\sb2N(TMS)\}\sb2V\sb2(\mu$-S)$\sb2.$ X-ray crystallographic analysis was not possible due to the poor quality of the crystals. However reaction of $\rm\lbrack (Me\sb3Si)\sb2N\rbrack\sb2VCI(THF)$ with S$\sb8$ yielded crystals of $\rm\{\lbrack (Me\sb3Si\sb2N\rbrack\sb2V\}\sb2(\mu$-S)$\sb2\}.$ On the other hand reaction of $\rm VCl\sb2(TMEDA)\sb2$ with S$\sb8$ led to the formation of $\rm VCl\sb3(TMEDA)(THF)$ and $\rm V\sb3S\sb7Cl(TMEDA)\sb3$ which precipitated as a black powder. Reaction of $\rm V\sb3S\sb7Cl(TMEDA)\sb3$ with mercaptopyridine led to the formation of $\rm\lbrack V\sb3(\mu\sb3$-Cl)-($\mu$-$\rm S\sb2)\sb3\rbrack (Psy)\sb3Li(THF)\sb4$ meanwhile the reaction of $\rm Me\sb3Si\sb2NLi$ yielded a high valent tetrameric structure $\rm \{\lbrack (TMS)\sb2N\rbrack VS\sb3Li(THF)\sb2Li\}\sb4$ complex. Alternative sources of sulfur atoms such as diphenyl disulfide was also used. In that particular case the reaction yielded a dimer which the X-ray structure confirmed as $\rm (TMEDA)\sb2V\sb2Cl\sb2(\mu$-SPh)$\sb2(\mu$-Cl). Ab initio and extended Huckel calculations were carried out on several clusters in order to understand the electronic structures of the complexes and the interactions between the metal centers. Calculations on a vanadium-sulfur cubane cluster revealed the presence of an intricate "web" of molecular orbitals showing electronic communication between all four metallic centers.

A new approach to prepare inorganic membranes has been developed. Those inorganic membranes are used in cation exchange, gas separation and in ultrafiltration processes. Clay and zeolite materials are used in the preparation of the inorganic membranes. First organic polymers are intercalated in kaolinite in order to improve the flexibility and to reduce cracks in the membranes. Sepiolite which is a natural hydrated magnesium silicate mineral with an interesting fibrous and porous morphology gives crack free membranes. The thickness of those unsupported membranes was 100-150$\mu$m. The main objective of this work was to prepare membranes with high percentages of microporosity in order to ensure a high selectivity in gas separation. For this purpose, zeolite was incorporated in the membrane together with sepiolite. The new inorganic membranes were tested and characterized using BET by adsorption-desorption of nitrogen to determine the microporosity, average pore diameter and pore size distribution. The porosity of these membranes were found to give a high surface area dominated by micropores. The membranes showed a good mechanical and thermal resistance. The liquid phase operation with microporous zeolitic materials is affected by the low diffusion rates of the liquids through the micropores. In cation exchange we have the diffusion through preferential pathways. Nevertheless, gas separation tests showed that although zeolitic membranes contained some connecting-through large pores, the relative fast diffusion of gaseous molecules through the zeolite micropores prevented their search for preferential diffusion pathways as in the case of liquid diffusing molecules.

Herein is reported a comparative study of the behaviour of four types of smectite clay minerals, mainly two poor iron bearing ones, SHCa-1 (hectorite from San Bernadino, California), SWy-1 (montmorillonite from Wyoming) and two ferruginous nontronites NG-1 (from Hohen Hagen, Germany) and SWa-1 (Grant County, Washington). The iron (III) exchange has been found to follow the cation exchange capacity (CEC) of the clays. This exchange has also been found to have no effect on the stability and the structure of the iron poor clay minerals while it has a slight effect on the crystallinity of the ferruginous clays and on their thermal stability. The intercalation has been found to be dependent on the expansibility of the clays, increasing from the nontronites (dioctahedral iron rich clays), to the montmorillonite (dioctahedral iron less rich clay) to hectorite (trioctahedral iron poor clay). This intercalation treatment has been found to have a slight effect on both the structure of the iron poor clays and their thermal stability. In contrast, the ferruginous ones undergo a dramatic change in both their structure and their thermal stability. The transition temperature to hematite occurred at 350°C as shown by an exotherm on the DSC curve of all the pillared materials. Furthermore the importance of iron oxyhydroxide and oxide phases formed were also found in both procedures to be dependent on the initial structural iron contents of the clays. We found that SH-modified SCa-3 and in SWa-1 have higher affinity for the metal ions than the SH-modified SWy-1 and in SHCa-1, because the pH of their solution is less acidic than those of SH-SWy-1 and SH-SHCa-1. All the adsorption isotherms followed the Langmuir model and the adsorbents could be easily regenerated by leaching out the metal with 0.1N HCl. Moreover, the adsorption study has shown a considerably higher affinity of the SH-clays towards Cd2+, Zn2+, than the iron modified clays (intercalated and pillared at 350°C and 600°C), the Na-clays, and the pure hematite. The competitive adsorption of the divalent metal cations showed a strong affinity of all the SH-clays for Cu2+ than for the Zn2+ and Cd2+, due to the low pH of the mixture solution which is equal to that of the Cu solution. (Abstract shortened by UMI.)

A series of V(III) catalysts with different substituted 1,3-dionates $\rm(V(acac)\sb3$ 2.1, V(Cy-$\rm acac)\sb3$ 2.2, V(t-Bu-$\rm acac)\sb3$ 2.3 and V(F-$\rm acac)\sb3$ 2.4 were prepared and characterized and their activities towards olefin polymerization were systematically compared. V(Cy-$\rm acac)\sb3$ 2.2 shows a slightly higher activity than the traditional catalyst $\rm V(acac)\sb3$ 2.1. The catalytically active species is relatively insensitive to modification of both the electronic and steric features of the acac ligand. The preparation of V(II) and V(IV) 1,3-dionate complexes was designed to study the role of the oxidation state of vanadium in terms of polymerization activity. Two unprecedented V(II) complexes (R-$acac)\sb2\rm V(TMEDA)$ (R = H(2.7), t-Bu (2.7c)) have been prepared and reacted with halocarbons to model the reactivation process. The isolation of (t-Bu-$acac)\sb2\rm V(TMEDA)\rbrack\lbrack X\rbrack\ \lbrack X = ZnCl\sb4\sp-$ 2.8, $\rm CuCl\sb2\sp-$ 2.9) indicates that the primary role of reactivating substances, commonly employed in the industrial processes, is to reoxidize V(II) to the trivalent state. Reaction of $\rm VCl\sb3(THF)\sb3$ with two equivalent of $\rm R\sp1(R\sp2)NLi{\cdot}Et\sb2O\ (R\sp1 = Ph,$ Bz; $\rm R\sp2 = Bz)$ gave the paramagnetic and monomeric $\rm\lbrack R\sp1(R\sp2)N\rbrack\sb4V$ (3.1) and (3.2). Reactions of $\rm VCl\sb3(THF)\sb3$ with one equivalent of $\rm R\sp1(R\sp2)NLi\ (R\sp1 = Bz;\ R\sp2 = Ph)$ and $\rm R\sb2NLi$ (R = Bz) formed the paramagnetic, monomeric $\rm\lbrack R\sp1(R\sp2)N\rbrack\sb3VCl$ (3.3) and $\rm\lbrack R\sb2N\rbrack\sb3VCl$ (3.4). Reaction of $\rm VCl\sb3(THF)\sb3$ with an excess of $\rm NaBH\sb4$ gave the paramagnetic and monomeric $\rm V(BH\sb4)\sb2(THF)\sb3$ (4.1), $\rm V(BH\sb4)\sb2(TMEDA)\sb2$ (4.2), and $\rm V(BH\sb4)\sb2(py)\sb4$ (4.3). (Abstract shortened by UMI.)

This work is concerned with the preparation and examination of guanidinate complexes. One method of synthesis of such ligands, as presented in Chapter 2, is the insertion of carbodiimide into a metal-amido group. The direct reactions of $\rm M(NMe\sb2)\sb5$ with either dicyclohexylcarbodiimide (CyN=C=NCy) or diisopropylcarbodiimide $\rm(\sp{i}PrN{=}C{=}N\sp{i}Pr)$ proceeded smoothly at room temperature under nitrogen to yield $\rm\lbrack RNC(NMe\sb2)NR\rbrack M(NMe\sb2)\sb4$ (M = Ta, Nb; R = Cy, $\rm\sp{i}Pr).$ The spectroscopic characterization of these materials is consistent with a symmetrical chelating bidentate guanidinate anion bonded to a pseudo-octahedral metal center. In chapter 3, we prepared $\rm N,N\sp\prime,N\sp{\prime\prime}$-tricyclohexylguanidine and triisopropylguanidine. With this guanidine ligand, we focus on the elimination of amido ligands from homoleptic Ta(V) and Nb(V) dimethylamido complexes. The complex $\rm TaCl(NMe\sb2)\sb3\{\lbrack CH\sb3)\sb2CHN\rbrack\sb2CN(H)CH(CH\sb3)\sb2\}$ was also isolated and crystallographically characterized. In Chapter 4, the direct reaction of Ta and Nb alkyl complexes $\rm M(Me)\sb{x}Cl\sb{y}$ (M = Ta, x = 3, y = 2; M = Nb, x = 2, y = 3) with $\rm N,N\sp\prime,N\sp{\prime\prime}$-tricyclohexylguanidine and $\rm N,N\sp\prime,N\sp{\prime\prime}$-triisopropylguanidine was investigated. The preliminary results of efforts to get a second alkyl elimination are also reported. (Abstract shortened by UMI.)

The chemistry of low-valent vanadium was extensively investigated especially in the organometallic field. Apart from cyclopentadienyl and alkoxides (or aryloxides) derivatives, its chemistry is poorly developed. Among the supporting ligands for the stabilization of low-valent vanadium, alkylamides need to be studied in more details. By introducing bulky amides such as $\rm R\sb2N\sp-\ (R = \sp{i}Pr,$ Cy, $\rm SiMe\sb3,\ C\sb6H\sb5,$ 3,5-Me$\sb2$Ph and Ad) in chemistry of vanadium(III) and vanadium(IV), we have opened a new field in the coordination of this early transition metal. Synthetic methodology is focused on the preparation of novel tris(amide) vanadium(III) complexes via transmetallation reaction of $\rm VCl\sb3(THF)\sb3$ with $\rm R\sb2NLi,$ using the stoichiometry ratio 1:3 and the same reaction conditions. Reaction of $\rm VCl\sb3(THF)\sb3$ with $\rm\lbrack(CH\sb3)\sb3Si\rbrack NPhLi$ led to the formation of the corresponding tetrahedral $\rm\{\lbrack(CH\sb3)\sb3Si\rbrack NPh\}\sb3V(THF)$ complex. Conversely, the reaction of $\rm CH\sb3C\lbrack(CH\sb2)N(\sp{i}Pr)Li\rbrack\sb3(TIAME)$ with VCl3(THF)$\sb3$ gave the new dinitrogen complex (TIAME)V-N$\sb2$-V(TIAME) whose structure was determined by X-ray analysis. The reaction of VCl$\sb3$(THF)$\sb3$ with (3,5-Me$\sb2$Ph)AdNLi.Et$\sb2$O (Ad = adamantyl) yielded the homoleptic vanadium(III) complex ((3,5-$\rm Me\sb2Ph)AdN\rbrack\sb3V$ which reacts with chalcogens E (E = S, Se) to yield diamagnetic terminal chalcogenide derivatives. The use of low-valent vanadium in the polymerization of olefins is poorly developed apart from acetylacetonato derivatives and chloride derivatives. The complexes of formula $\rm(R\sb2N)\sb2VCl\sb2$ (R = $\rm\sp{i}$Pr, Cy) provide a unique example of oxidative disproportionation. The formation of dicyclahexyl and diisopropyl derivatives is the result of oxidative coupling of two low-valent vanadium entities. The first to be formed is the bis(amido)V$\rm\sp{IV}Cl\sb2$ followed by the unstable "$\rm V\sp{II}Cl\sb2$". The stability of the novel vanadium(IV) bisamido complexes allowed us to investigate their reactivity towards olefin polymerization.

No description available.

A recent drive to explore the fundamental properties of later actinide elements is culminated by this research which targets the structural chemistry and electronic behavior of berkelium in the solid-state. Experimental evidence collected for materials containing plutonium, americium, curium, and californium have stirred interest in revising models explaining bonding character in the actinides. Covalency in chemical bonding is linked to the differences in crystalline structure which these elements possess upon reaction under identical experimental conditions. Moderate half-lives and dangerous decay energies provide obstacles for actinide research in terms of safety and handling, but production of milligram quantities of these elements at HFIR in ORNL overcomes the major concern of sufficient yield in material. The first four single crystal berkelium materials to exist were developed in solvothermal [Bk(HDPA)₃·nH₂O], flux {Bk[B₆O₈(OH)₅]}, and hydrothermal synthesis reactions [Bk(IO₃)₃ and Bk(IO₃)₄]. In a series of experimental and quantum mechanical techniques, the bonding dynamics of berkelium could be related to its actinide neighbors, curium and californium, as well as its lanthanide isoelectronic analog, terbium. The results support the introduction of hybridized 5f6d bonding orbitals in the trivalent berkelium materials, something which is absent in corresponding curium and terbium compounds, but present in those with californium. Quantum mechanical calculations expose this observation and isotypic structure-types between berkelium and californium, and not curium or terbium, corroborate this finding. However, splitting of the ground state energy by spin-orbit coupling is an order of magnitude smaller in berkelium, like curium, compared to californium. Therefore, conclusions of berkelium’s bonding nature can be resolved to show structural chemistry akin to californium, but electronic behavior similar to curium. The first "formally" tetravalent berkelium material, Bk(IO₃)₄, displayed spectroscopic behavior of trivalent berkelium, a property known as mixed-valency. These bulk-scale experiments expose the unique fundamental chemistry of berkelium, an endeavor that is difficult to achieve when considering the half-lives of and protection against the decay energies of ²⁴⁹Bk and ²⁴⁹Cf, the daughter of ²⁴⁹Bk. Disruption of typical electronic behavior in the earlier actinides was sought by slow evaporation and solid-state characterization experiments. A typical reductant used in nuclear separations to maintain Pu[superscript IV] and Np[superscript IV] and leave U[superscript VI], FHA was used as a complexing ligand in crystallization experiments with U[superscript VI] and Pu[superscript IV]. Crystallization of UO₂(FHA)₂ produced red block crystals, where the atypical red color from yellow-green is a result of distortions in the absorption of this material due to weakening of the O=U=O bond by 6.5° from linear. Pu₂(FHA)₈ crystallizes as a discrete dimeric complex, with inversion symmetry that may be a key to observing the nuclear moment of plutonium using ²³⁹Pu-NMR. Reversing the role of FHA from reductant to ligand provided evidence of strong π donation in actinide complexes that suggest its application in uranium seawater extraction. Finally, collaborative work between CEMRC and INE aims at producing a model that explains actinide solubility data in high ionic strength borate media. Undersaturation experiments with Np[superscript V] represent the final measurements needed to effectively model its solubility and speciation behavior in high ionic strength brine solutions of similar consistency to that of natural geological repositories. Preliminary analysis of Pu[superscript VI] in varying borate solutions expose two different species of plutonium borate, a result of the ability for borate to polymerize in aqueous media. This dissertation is the collective work of three projects in two different topic areas. The work is presented in chronological order of experiment and publication. Chapter four and five review the effects in structure and bonding in UO₂(FHA)₂ and Pu₂(FHA)₈ due to the coordination by FHA. Chapters six and seven expose the fundamental chemistries of berkelium and its qualities in relation with its neighbors in the actinide series. Speciation and solubility data for Np[superscript V] and Pu[superscript VI] borate systems are discussed in chapter eight and nine. Collectively, this work explains unique phenomena in higher valent actinide complexes, the distinct behavior of berkelium in sold-state, and the migration of Np[superscript V] and Pu[superscript VI]. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the Doctor of Philosophy. / Fall Semester 2016. / November 17, 2016. / Includes bibliographical references. / Thomas E. Albrecht-Schmitt, Professor Directing Dissertation; Theo Siegrist, University Representative; Susan Latturner, Committee Member; Michael Shatruk, Committee Member.

Flux synthesis of new complex compounds uses an excess of molten metals or salts as a reaction medium. This solution-based method is a valuable tool in materials synthesis, enabling the solid-state chemist to achieve reactivity at relatively low temperatures compared to traditional solid-state reactions. A growing effort in the field of flux synthetic chemistry is to enable the directed synthesis of materials. This entails being able to predict products that will form, or at least the building blocks that will be incorporated into the products. It is therefore necessary to explore various flux systems in order to develop trends that will better help chemists understand the mechanisms by which compounds and their building blocks form. To this end, two flux mixtures, Ca/Li and Yb/Li, were explored and several new complex compounds were discovered which feature a range of structural and electronic properties. Calcium and ytterbium commonly form solid solutions in compounds due to similarities in their ionic radii and valence. Calcium melts above 800°C, but the addition of lithium lowers this melting point drastically to around 300°C. Unfortunately, there is no phase diagram for mixtures of ytterbium and lithium, so attempts to grow new crystals in this melt was largely speculative on the basis that ytterbium may behave similarly to calcium and produce a low-temperature solution when mixed with sufficient lithium. This is supported by the fact that ytterbium has a similar melting point to calcium, and binary phase diagrams incorporating ytterbium or calcium mixed with other metals feature similar trends. Ca/Li flux is able to dissolve refractory elements such as carbon, as well as salts such as Ca3N2 and CaH2. New carbide and hydride compounds formed from Yb/Li flux suggest similar capabilities, however reactivity with nitride salts is still undetermined. Electropositive fluxes in general are useful solvents for the growth of new complex carbides, nitrides and hydrides. Compounds containing these light elements are extremely important for many industrial applications. Therefore, further exploration into making new complex compounds incorporating them is merited. Several new compounds including Ca12InC13-x, Ca6Te3N2, Ca6(LixFe1-x)Te2N3, Ca8In2SiN4, Ca3SiN3H, and Yb~51In13H27 were synthesized from either Ca/Li or Yb/Li flux mixtures. Their synthesis, structural and electronic properties, as well as potential applications are discussed herein. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2017. / November 09, 2017. / Includes bibliographical references. / Susan Latturner, Professor Directing Dissertation; Theo Siegrist, University Representative; Thomas Albrecht-Schmitt, Committee Member; Igor V. Alabugin, Committee Member.