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Microwaves have been for their ability to heat water and food rapidly. And thanks to scientific technology and global marketing, the microwave oven was invented and got widely used in 1970's and 1980's. . Microwave radiation has specific...
Study of redox and complexation interactions of neptunium with humic acid and chemical analogs
Description:
The redox and complexation interactions of neptunium with humic acid and chemical analogs are studied in this research by solvent extraction and spectrophotometry. In the redox study, dicarboxylic acids and substituted phenolic compounds are selected as models for humic acids. Np(VI) is found to be reduced to Np(V) by both series of compounds, but phenolic compounds reduce Np(VI) more rapidly under... Np(VI) is reduced rapidly by humic acid to Np(V), which exists as free Np(V) and Np(V)-humate complex. In the subsequent study of complexation between Np(V) and humic acid, Np(V) is found to form a single type of complex with humic acid...
KINETIC STUDIES OF NEPTUNIUM(VI) REDUCTION REACTIONS WITH KOJIC ACID AND TROPOLONE
Description:
For safe disposal of nuclear wastes, it is necessary to improve our understanding on the long-term behavior of long-lived actinides in the environment. With respect to the problems of potential migration of radionuclides from a nuclear... From results on the kinetic studies of these reactions, the NpO(, 2)('++) is reduced to the NpO(, 2)('+) in a one-electron transfer process with no structural change of the dioxo neptunium species. The rates for both reactions are directly... The activation parameters for the Np(VI) reduction with kojic acid and tropolone have the same values within the uncertainties: i.e., (DELTA)H('(NOT=)) = 82.7 (+OR-) 3.4 KJ/mol, (DELTA)S('(NOT=)) = 34 (+OR-) 12 J/mol/deg for kojic acid...
Out of interest in better exploring the nature of actinide bonding, investigations have been undertaken which confront the problem of the unusual character of covalency as it occurs in the 5f elements by utilizing multiple analytical...
The search for alternative nuclear fuels, materials suitable for nuclear waste repositories, and new superconducting materials has been underway for decades. We have explored metal flux and mixed-metal flux synthesis and supercritical...
Contained in this dissertation is an analysis of the fundamental chemistry of the f-block elements with oxygen donor ligands in ionic liquids. This work focuses heavily on the structures of the crystalline phases that form when...
Spectroscopic studies of lanthanide complexes with organic ligands
Description:
The effect of concentration of Eu(III) on its lumnescence decay constant and complexation of trivalent lanthanides with aromatic (mellitic, pyromellitic, hemimellitic, trimellitic, trimesic, phthalic, isophthalic, terephthalic and... At constant ionic strength (0.1 M NaClO$\sb4$), Eu(III) luminescence decay constant increases as its concentration decreases from 0.2 M to 10$\sp{-5}$ M while the Eu(III) $\rm\sp7F\sb0\to$ $\sp5D\sb0$ excitation spectra were unchanged. Both luminescence spectra and decay constants indicate that mellitate, pyromellitate, hemimellitate, trimellitate, trimesate and terephthalate form ML complex while phthalate, isophthalate, benzoate and the aliphatic dicarboxylates form... The oscillator strengths of Nd(III) and Ho(III) complexes with carboxylates in the hypersensitive trantion ranges were calculated and the relationships between stability constant, oscillator strength and ligand basicity were examined. Luminescence and NMR studies show that Eu(III) forms ML, ML$\sb2$, and ML$\sb3$ complexes with ethylenediamine in DMSO. The quenching effect of N-H on Eu(III) and Tb(III) luminescence is linearly proportional to the number of N-H groups... It was found that formation of Eu(III) complexes causes shift of the maxima of Eu(III) $\rm\sp7F\sb0\to$ $\sp5D\sb0$ excitation spectra towards lower frequency. The magnitude of the shift linearly correlates with the total ligand...
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...
This dissertation seeks to determine fundamental differences between lanthanides and actinides, as well as how their bonding influences ligand selectivity, for possible actinide separations from nuclear waste. The f-elements are...
THE KINETICS OF THORIUM-POLYELECTROLYTE INTERACTION (SPECTRUM)
Description:
The rate constants for thorium dissociation from humic acid, PMA (polymaleic acid) and PMVEMA (poly -methylvinylether/maleic acid ) were measured in the pH range of 4.20 to 5.94. The rate of thorium dissociation from these... The dissociation of thorium from these polyelectrolytes occurred by several first order pathways. These pathways fit into two categories based on their dependence on pH, temperature and the amount of time thorium was in contact with the... The second category of dissociation pathways was interpreted as dissociation of thorium from binding sites located within the coiled structure of the polyelectrolyte. This type of bound thorium formed very slowly and had small...
PREPARATION AND CHARACTERIZATION OF METAL ION COMPLEXES OF (N,N)-DIMETHYLETHYLENEDIAMINE N-OXIDE, BETA-AMINOETHYL TRIMETHYLAMMONIUM PERCHLORATE AND GAMMA-AMINOPROPYL TRIMETHYLAMMONIUM PERCHLORATE
SYNTHESIS, CHARACTERIZATION, AND REACTIONS OF EARLY TRANSITION-METAL COMPLEXES WITH PORPHYRINS AND OTHER TETRAAZA-MACROCYCLIC LIGANDS
Description:
The chemistry of early transition elements (Ti, V, Mo, W) with the macrocyclic ligands C(, 22)H(, 24)N(, 4) and H(, 2)TPP (tetraphenylporphyrin) has been demonstrated to be more versatile than the exhaustively studied macrocyclic complexes... New (mu)-oxo bridged heterobinuclear dimer complexes have been obtained from the reaction of titanyl and vanadyl species with other metal complexes. The V=O group of VO(C(, 22)N(, 4)) reacts with highly oxophilic Lewis acids such as... Mo(CO)(, 6) reacts with H(, 2)TPP to yield a molybdenum-molybdenum quadruply bonded dimer complex. This discovery, in essence, corrects a fifteen year old literature report, which originally reported the synthesis of Mo(O)(OH)(TPP). The... W(V) porphyrin complexes react with H(, 2)O(, 2) yielding an unusual tungsten (VI) porphyrin complex having oxo and peroxo groups in cis coordination positions. Furthermore these groups are eclipsed with respect to the porphyrin nitrogen... Ti(C(, 4))Cl(, 2) reacts with NaC(, 5)H(, 5) yielding a new type of sandwich complex Ti(C(, 4))(C(, 5)). It consists of a minicycle (C(, 5)('1-)) and the tetraazo macrocyclic C(, 4)('2-).
THERMODYNAMICS OF CALCIUM, MAGNESIUM AND LANTHANIDE COMPLEXATION WITH ADENOSINE PHOSPHATES
Description:
Complexation of calcium and magnesium with adenosine mono, di and tri phosphates has been studied at 25(DEGREES)C and 0.1 M ionic strength. Stability constants for the complexes with unprotonated as well as the monoprotonated forms of... Complexation of lanthanide ions with adenosine mono and tri phosphates has been studied at 0.1 M ionic strength (NaClO(, 4)). The stability constants for unprotonated and monoprotonated complexes have been determined by potentiometry and... Complexation of sodium ions with adenosine triphosphate has been studied to evaluate its effect on the metal complexation study. The corrections are estimated for the observed complexation constants and the thermodynamic parameters. The studies show that the adenosine phosphates are bound to the alkaline earth cations mainly through the phosphate chain. The interaction of the base (adenine) is either not present or is negligible. The complexation of lanthanide ions...
FACTORS INFLUENCING METAL-CARBON BOND REACTIVITY WITH EMPHASIS ON ALUMINUM ALKYLS
Description:
The objective of this dissertation was to test the hypothesis that constrained ligand environments can influence the stability of aluminum-carbon bonds. The synthesis and characterization of a variety of organo-aluminum complexes of...
Spectroscopic studies of neptunium(V) complexation
Description:
The complexation of Np(V) with aliphatic (oxalic, malonic, succinic, glutaric, and maleic) and aromatic (phthalic, pyromellitic, hemimellitic, trimellitic, and mellitic) polycarboxylic acids was studied by spectrophotometry at 1 M ionic... In polycarboxylate systems, the stability constant decreased in the order hemimellitate $>$ mellitate $>$ pyromellitate $>$ trimellitate, phthalate. With the exception of hemimellitate, this trend follows the order of decreasing basicity... The unexpected strength of hemimellitate complexation was attributed to an increase in electron density at the binding site from the non-chelating carboxylate group through induction. The complexation of phthalate, trimellitate and hemimellitate and mellitate were studied as a function of pH. Trimellitate and mellitate were found to form MHL as well as ML complexes while for phthalate and hemimellitate only ML species... The stability constants of the cation-cation complexes Np(V)-U(VI) and Np(V)-Np(V), measured at 6 M ionic strength (HClO$\sb4$) and 25$\sp\circ$C, were found to be 2.45 $\pm$ 0.05 and 1.41 $\pm$ 0.14, respectively. The change in enthalpy...
The fundamental chemistry of the f-elements is relatively underexplored compared to any other block of elements on the periodic table. The synthesis, structure determination, and characterization of new f-element compounds may lead to...
The rapid synthesis of x-ray pure yttrium barium(2) copper(3) oxygen(7)
Description:
This paper describes a variation of the oxalate procedure that has significant advantages. The oxalate approach is often used to produce rare earth 123 superconductors and related ceramics. A moderately high concentration of acetone... When oxalic acid or oxalate ions are added to a yttrium-barium-copper aqueous solution, significant amounts of the metal (typically 10-40% of either Cu or Ba depending upon the pH) are left in solution. Such losses result in poor quality...
This dissertation focuses on probing the fundamental chemistry of the actinide series, specifically the structure and bonding in complexes of transuranium elements. The actinides consist of the elements from actinium to lawrencium in the...
THE HEXAVALENT ACTINIDES: SOME NEW DIRECTIONS IN THE STUDY OF REDOX KINETICS AND COMPLEXATION THERMODYNAMICS
Description:
The environmental behavior of the actinide elements will depend on their redox and complexation chemistries. Chapter I of this Dissertation briefly reviews actinide solution chemistry on the fundamental and applied (i.e. environmental)... Solvent extraction by thenoyltrifluoracetone was found suitable for investigation of tracer-level actinide redox reactions. This technique was employed in the study of reactions of Np(VI) with water-soluble carboxylates, phenols, and... Chapter III describes the development and characteristics of a coated-wire electrode specific for actinyl cations. The electrode was found to respond rapidly and reproducibly to 10('-5) - 10('-2) M U(VI) with a slope almost twice that... The results of an investigation of the thermodynamics of Pu(VI) complexation by bicarbonate at pH 8 are presented in Chapter IV. From the previously determined 1:1 stability constant and from calorimetric data, the stability constant for...
Molecular photophysics and metal coordination chemistry are the two fundamental pillars that support the development of fluorescent cation indicators. In this article, we describe how Zn(II)-coordination alters various ligand-centered...
Spectroscopy and electrochemistry of uranium complexes in aluminum chloride-1-ethyl-3-methylimidazolium chloride
Description:
The redox chemistry of UCl$\sb4$ was investigated in the solvent AlCl$\sb3$-1-ethyl-3-methylimidazolium chloride (AlCl$\sb3$-EMIC), a room temperature ionic liquid. In basic solutions (
Distinguishing Förster resonance energy transfer and solvent-mediated charge-transfer relaxation dynamics in a zinc(II) indicator: a femtosecond time-resolved transient absorption spectroscopic study
A bifluorophoric molecule (1) capable of intramolecular Förster Resonance Energy Transfer (FRET) is reported. The emission intensity of the FRET acceptor in 1 depends on the molar absorptivity of the donor, which is a function of zinc(II...
This PhD thesis is devoted to investigation of inorganic materials with low-dimensional structures. Such materials attract significant fundamental and applied interest due to the potential to achieve highly anisotropic properties, which...
In this work, various transition and main group metals were heated in a low temperature molten sulfur/iodine flux to produce metal sulfides and metal sulfide iodides, in a one-pot synthesis method that eliminates the use of toxic or...
An improved method has been developed for the preparation of 5-iodo-1, 2, 3-triazoles directly from organic azides and terminal alkynes by a reaction mediated by copper(I) and iodinating agents generated in situ. The major methodological...
The design and investigation of bimetallic ruthenium complexes exhibiting proton-coupled intramolecular electron transfer
Description:
The development and investigation of bimetallic systems that undergo proton-coupled intramolecular electron-transfer are reported. Initial studies involved the synthesis of a new family of synthetically versatile ruthenium complexes...
GROUND STATE PROPERTIES OF CESIUM COBALT TRICHLORIDE AND OPTICAL SELECTION RULES FOR EXCITONS AND MAGNONS IN MAGNETIC PHASES OF CESIUM COBALT TRICHLORIDE AND CESIUM NICKEL TRICHLORIDE
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...
N-Alkyl-N, N-di(2-pyridylmethyl)amines are ligands commonly used by supramolecular chemists in molecular recognition and sensing applications. The metal coordination complexes of these ligands, in particular those with 2:1 (ligand:metal)...
The kinetics of rare earth element interactions with synthetic and naturally occurring polyelectrolytes
Description:
This research is an investigation of the kinetics of formation and dissociation of complexes of trivalent lanthanide ions with the polyelectrolytes polyacrylic acid and humic acid. Theories of cation binding to charged polymers have... Ultrafiltration and ion exchange studies indicate that under the conditions of this study, complexation is fast and complete, but slowly changes from the initially labile interactions to a distribution of the cations between labile sites... Decomplexation has been studied using a ligand exchange technique, and the binding sites appear to fall into two classes of interactions based on their dissociation rates. The first category of interactions dissociates rapidly, and...
The periodic table of the elements, derived from numerous attempts in the 1800s to systematically examine the chemistry found in nature, has seen a stark evolution over the last century. The elements of the actinide series are the...
Despite their discovery during the 1940's, there are still many unanswered questions surrounding the elements past uranium, or transuranic elements. In the recent years more evidence is emerging that suggest the bonding and structure of...
The knowledge of actinide chemistry significantly lags behind the rest of the periodic table. Understanding the fundamental behavior of these elements is crucial for actinide separations and nuclear waste storage. Many separation...
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