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Some of the material in is restricted to members of the community. By logging in, you may be able to gain additional access to certain collections or items. If you have questions about access or logging in, please use the form on the Contact Page.
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...
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...
The complex formation of UO(, 2)('+2), Ca('+2) and Th('+4) with halates, acetate and haloacetates has been studied by means of solvent extraction. The stability constants have been determined for UO(, Ca('+2) and Th('+4) with...
The actinide elements are playing larger roles in modern life, finding uses in nuclear energy, remote power sources, medical uses as radiotherapy isotopes, as well as in geological applications in nuclear tools. However, due to their...
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...
Spin-crossover (SCO) is one of the most recognized spin-state switching phenomena as an example of molecular bistability. The ability to convert between high spin and low spin electronic configurations in a transition metal center under...
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...
In the 2018 Nuclear Posture Review, it has been emphasized that the continued production of nuclear materials is and will continue to be an essential part of American interest and policy. Necessarily, the cleanup and environmental...
Spin crossover (SCO) is a phenomenon of magnetic switching in transition metal complexes that can exist in two different electronic configurations, depending on the splitting of d-orbitals by the surrounding ligand field. About 90% of...
The focus of this dissertation is to study the magnetic properties of several novel transition metal complexes, with particular emphasis on using SQUID magnetometry alongside electron paramagnetic resonance (EPR) and spectral simulations...
Crystalline intermetallic phases grown by metal flux synthesis are discussed in terms of structure-property relationships. Flux growth is employed as the primary synthesis methods across different systems from single element fluxes like...
Metal flux synthesis is a useful technique for the discovery of novel intermetallic phases. The molten state enhances diffusion rates which improves rates of reaction. Reactions can proceed at lower temperatures, allowing for the...
Synthesis, characterization, and reactivity of group 6 metal (molybdenum and tungsten) complexes with porphyrin ligands
Description:
The structures, physical properties, and reaction chemistry of molybdenum (V) and tungsten (V) porphyrin complexes are investigated. The four, five-coordinate nitrido molybdenum (V) and tungsten (V) complexes MoN(TMP), MoN(TPP), MoN(TTP)... Quadruply bonded (W(TPP)) $\sb2$ and its reaction derivative WN(TPP) also have been synthesized. Diamagnetic tungsten dimer (W(TPP)) $\sb2$ shows the very similar spectroscopic patterns to those of (Mo(TPP)) $\sb2$. Temperature dependent...
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...
Understanding the chemical and biological innovation and evolution of the global ocean is pivotal in understanding the processes involved in the evolution and proliferation of early life on Earth and potentially habitable exoplanets....
Flux synthesis is a useful method for the exploration and development of new tetrelide Zintl phases. Reactions of heavy divalent metals (A = Ca, Sr, Ba, Eu, Yb) with tetrels (Tt = Si, Ge, Sn) in Mg/Al flux mixtures produce charge...
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...
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...
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-).
PREPARATION AND CHARACTERIZATION OF METAL ION COMPLEXES OF (N,N)-DIMETHYLETHYLENEDIAMINE N-OXIDE, BETA-AMINOETHYL TRIMETHYLAMMONIUM PERCHLORATE AND GAMMA-AMINOPROPYL TRIMETHYLAMMONIUM PERCHLORATE
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...
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...
The substitution of the Group VIIB dimetal decacarbonyls with trifluorophosphine
Description:
Substitution of CO with PF$\sb3$ in the Group VIIB dimetal decacarbonyls has been studied under thermal and photolytic conditions. Substitution via photolysis is faster and results in the production of a greater number of isomers. Under...
Models for proton-coupled electron transfer based on ruthenium polypyridyl complexes
Description:
A family of ruthenium (II) complexes have been synthesized such that oxidation of the metal is coupled to an acid-base reaction at a remote site of a coordinated ligand. Proton-coupled electron transfer was evaluated based on cyclic...
Mechanistic studies of the group 6 metal carbonyl trifluorophosphines
Description:
The M(CO)$\sb{\rm 6-x}$(PF$\sb3$)$\sb{\rm x}$ complexes where M is Cr, Mo and W and x is 0 to 6 are known. The reactivity of both isomeric forms of the complexes x = 2 and 3 with $\sp{13}$CO and PF$\sb3$ were studied under purely thermal... isomer in large relative yields are discussed. These reactions were studied with packed column gas chromatography and infrared spectroscopy.
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...
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 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...
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...
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