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Aqueous Ln(III) Luminescence Agents Derived from a Tasty Precursor

Description: The synthesis, aqueous stability and photophysical properties are reported for a novel tetradentate ligand derived from maltol, a commonly used flavor enhancer. In aqueous solution, this chelate forms stable complexes with Ln(III) cations, and sensitized emission was observed from Eu(III), Yb(III), and Nd(III). A comparison with recently reported and structurally analogous ligands reveals a slightly higher basicity but lower complex stability with Eu(III) [pEu = 14.7 (1)]. A very poor metal centered quantum yield with Eu(III) was observed ({Phi}{sub tot} = 0.04%), which can be rationalized by the similar energy of the ligand triplet state and the Eu(III) {sup 5}D{sub 0} emissive level. Instead, sensitized emission from the Yb(III) and Nd(III) cations was observed, which emit in the Near Infra-Red (NIR).
Date: June 2, 2008
Creator: Jocher, C.J.; Moore, E.G.; Pierce, J.D. & Raymond, K.N.
Partner: UNT Libraries Government Documents Department

Complexation of Lactate with Nd(III) and Eu(III) at Variable Temperatures: Studies by Potentiometry, Microcalorimetry, Optical Absorption and Luminescence Spectroscopy

Description: Complexation of neodymium(III) and europium(III) with lactate was studied at variable temperatures by potentiometry, absorption spectrophotometry, luminescence spectroscopy and microcalorimetry. Stability constants of three successive lactate complexes (ML{sup 2+}, ML{sup 2+} and ML{sub 3}(aq), where M stands for Nd and Eu, and L stands for lactate) at 10, 25, 40, 55 and 70 C were determined. The enthalpies of complexation at 25 C were determined by microcalorimetry. Thermodynamic data show that the complexation of trivalent lanthanides (Nd{sup 3+} and Eu{sup 3+}) with lactate is exothermic, and the complexation becomes weaker at higher temperatures. Results from optical absorption and luminescence spectroscopy suggest that the complexes are inner-sphere chelate complexes in which the protonated {alpha}-hydroxyl group of lactate participates in the complexation.
Date: October 1, 2010
Creator: Tian, Guoxin; Martin, Leigh R. & Rao, Linfeng
Partner: UNT Libraries Government Documents Department

Me-3,2-HOPO Complexes of Near Infra-Red (NIR) Emitting Lanthanides: Efficient Sensitization of Yb(III) and Nd(III) in Aqueous Solution

Description: The synthesis, X-ray structure, solution stability, and photophysical properties of several trivalent lanthanide complexes of Yb(III) and Nd(III) using both tetradentate and octadentate ligand design strategies and incorporating the 1-methyl-3-hydroxy-pyridin-2-one (Me-3,2-HOPO) chelate group are reported. Both the Yb(III) and Nd(III) complexes have emission bands in the Near Infra-Red (NIR) region, and this luminescence is retained in aqueous solution ({Phi}{sub tot}{sup Yb} {approx} 0.09-0.22%). Furthermore, the complexes demonstrate very high stability (pYb {approx} 18.8-21.9) in aqueous solution, making them good candidates for further development as probes for NIR imaging. Analysis of the low temperature (77 K) photophysical measurements for a model Gd(III) complex were used to gain an insight into the electronic structure, and were found to agree well with corresponding TD-DFT calculations at the B3LYP/6-311G{sup ++}(d,p) level of theory for a simplified model monovalent sodium complex.
Date: November 10, 2009
Creator: Moore, Evan G.; Xu, Jide; Dodani, Sheel; Jocher, Christoph; D'Aleo, Anthony; Seitz, Michael et al.
Partner: UNT Libraries Government Documents Department

High-Relaxivity MRI Contrast Agents: Where Coordination Chemistry Meets Medical Imaging

Description: The desire to improve and expand the scope of clinical magnetic resonance imaging (MRI) has prompted the search for contrast agents of higher efficiency. The development of better agents requires consideration of the fundamental coordination chemistry of the gadolinium(III) ion and the parameters that affect its efficacy as a proton relaxation agent. In optimizing each parameter, other practical issues such as solubility and in vivo toxicity must also be addressed, making the attainment of safe, high-relaxivity agents a challenging goal. Here we present recent advances in the field, with an emphasis on the hydroxypyridinone family of Gd{sup III} chelates.
Date: January 15, 2008
Creator: Werner, Eric J.; Datta, Ankona; Jocher, Christoph J. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

Abstract of Paper Presented at the Symposium on Metal ChelateChemistry at Brooklyn Polytechnic Institute on April 26, 1952

Description: The essential structural element which differentiates metal chelate compounds from metal coordination compounds, or metal complexes in general, is the existence of some linkage between two or more of the donor atoms in the first coordination sphere of the metal. It is the purpose of the present discussion to examine the influences that this structural factor may have upon the physical and chemical properties of chelate compounds. Examples of well known, simple coordination compounds involving a variety of donor atoms (Oxygen, nitrogen), as well as a variety of electrostatic situations are shown in the following formula. Below each one are listed a few corresponding chelate structures.
Date: April 1, 1952
Creator: Calvin, Melvin
Partner: UNT Libraries Government Documents Department


Description: The formation constants of the RChOH/sup -/ species, formed by interaction of individual rare-earth nitrilotriacetate species and KOH at 25 deg C and an ionic strength of 0.1 were determined by the potentiometric method, i.e., computed from the pH values of equilibrium mixtures containing varying proportions of rare-earth complex and base. The relations of these constants to the ion-exchange separation of rare earths at high pH were discussed. (auth)
Date: April 13, 1962
Creator: Gupta, A.K. & Powell, J.E.
Partner: UNT Libraries Government Documents Department

Failure of cooling tower LOB-CT-1

Description: Following the loss of cooling tower LOB-CT-1, an investigation was conducted to determine the cause and to develop precautions to prevent future cooling tower losses. This cooling tower, located in the office-building basement of the Clinton P. Anderson Los Alamos Meson Physics Facility (LAMPF), was shut down on October 29, 1973. Excessive use of chelate chemical was ludged to be the major factor involved in the high corrosion rates observed. A number of precautions are listed which should prevent further surprise'' corrosion problems. The precautions include precalculation of chemical additions, visual inspection, corrosion coupons, corrosion meters, and chemical analyses of operating conditions. (auth)
Date: March 1, 1974
Creator: Midkiff, W.S.
Partner: UNT Libraries Government Documents Department

High Relaxivity Gadolinium Hydroxypyridonate-Viral Capsid Conjugates: Nano-sized MRI Contrast Agents

Description: High relaxivity macromolecular contrast agents based on the conjugation of gadolinium chelates to the interior and exterior surfaces of MS2 viral capsids are assessed. The proton nuclear magnetic relaxation dispersion (NMRD) profiles of the conjugates show up to a five-fold increase in relaxivity, leading to a peak relaxivity (per Gd{sup 3+} ion) of 41.6 mM{sup -1}s{sup -1} at 30 MHz for the internally modified capsids. Modification of the exterior was achieved through conjugation to flexible lysines, while internal modification was accomplished by conjugation to relatively rigid tyrosines. Higher relaxivities were obtained for the internally modified capsids, showing that (1) there is facile diffusion of water to the interior of capsids and (2) the rigidity of the linker attaching the complex to the macromolecule is important for obtaining high relaxivity enhancements. The viral capsid conjugated gadolinium hydroxypyridonate complexes appear to possess two inner-sphere water molecules (q = 2) and the NMRD fittings highlight the differences in the local motion for the internal ({tau}{sub RI} = 440 ps) and external ({tau}{sub RI} = 310 ps) conjugates. These results indicate that there are significant advantages of using the internal surface of the capsids for contrast agent attachment, leaving the exterior surface available for the installation of tissue targeting groups.
Date: August 29, 2007
Creator: Meux, Susan C.; Datta, Ankona; Hooker, Jacob M.; Botta, Mauro; Francis, Matthew B.; Aime, Silvio et al.
Partner: UNT Libraries Government Documents Department

Reactivity of Five-Coordinate Intermediates Derived from (Chelate) Tetracarbonylmetal (0) Complexes

Description: The reactivity of the [(Phen)Cr(CO)_3] intermediate with phosphines and phosphites (L) has been investigated through ligand-competition studies. This intermediate possesses virtually no ability to discriminate among L. The agreement between reactivity data for the thermal and photochemically-generated intermediates indicates that the same intermediate is produced via each process. Pulsed laser flash photolysis of (n^2-NP)M(CO)_4 (I) (M = Cr, Mo; NP = 1-diethylamino-2-diphenylphosphinoethane) in the absence and presence of P (OPr-i)_3 (L) in 1,2-dichloroethane and chlorobenzene induces unimolecular ring-opening to afford [(n^1-NP)M(CO)_4] (II), in which the bidentate ligand is coordinated through P. Reaction of this intermediate takes place through competitive ring-reclosure and attack at (II) by L to afford (I) and cis-(n^1-NP) (L)M(CO)_4.
Date: December 1983
Creator: Mansour, Saber E. (Saber El-Sayed)
Partner: UNT Libraries

Kinetics and Mechanisms of Ligand Exchange Reactions of Chelate Complexes

Description: Certain ligand substitution reactions proceed to a complete displacement of the chelate ligand. Certain reactions proceed through a mechanism involving an initial fission of the tungsten-sulfur bond to afford a coordinatively-unsaturated intermediate which is rapidly attacked by chlorobenzene. The resulting solvated intermediate establishes an equilibrium which involves desolvation-solvation. Although main group organometallic chemistry has received a great deal of attention, this discussion will be centered in organotransition metal chemistry, in particular, metal carbonyls.
Date: May 1989
Creator: Cortés, José E. (José Enrique)
Partner: UNT Libraries

Contaminant Organic Complexes: Their Structure and Energetics in Surface Decontamination

Description: The Department of Energy has a goal of decontaminating an estimated 180,000 metric tons of metal wastes in various surplus facilities. Uranium (U) and other radioactive actinides and lanthanides are embedded within the mixed oxide structures of the passivity layers of corroded iron and steel. These toxic metals can be dissolved out of the surface layers by a naturally occurring bacterial siderophore called Desferrioxamine B (DFB). DFB is a trihydroxamate ligand with one amine and three hydroxamate groups, which chelates with metals through hydroxamate coordination. Complexation of DFB with U can be utilized in decontamination strategy of the passivity layers. Therefore, we have been studying reactions of uranyl U(VI) with zerovalent iron (Fe0) followed by dissolution by DFB. The objectives were to determine the structure and speciation of solution and solid phases of U and to assess the effectiveness of DVB in U dissolution.
Date: July 12, 2005
Creator: Traina, Samuel & Sharma, Shankar
Partner: UNT Libraries Government Documents Department

Phytosiderophore Effects on Subsurface Actinide Contaminants: Potential for Phytostabilization and Phytoextraction

Description: This project seeks to determine the potential of phytosiderophore-producing plants for phytostabilization and phytoextraction of actinides and some metal soil contaminants. Phytosiderophores are secreted by graminaceous plants such as barley and wheat for the solubilization, mobilization and uptake of Fe and other essential nutrients from soils. The ability for these phytosiderophores to chelate and absorb actinides using the same uptake system as for Fe is hereby investigated though characterization of actinide-phytosiderophore complexes (independently of plants), and characterization of plant uptake of such complexes.
Date: June 1, 2003
Creator: Ruggiero, Christy
Partner: UNT Libraries Government Documents Department

A Comparison of Methods Used to Evaluate Intakes of Transuranics Influenced by Chelation Therapy

Description: A comparison of methods is used to evaluate the intake of transuranics influenced by chelation therapy. The purpose of this paper is to introduce the mechanistic method by using it to validate Hall's method and Jech's method. This is accomplished by using the mechanistic method to generate a known set of data suitable for benchmarking all three methods.
Date: May 14, 2002
Creator: La Bone, T.
Partner: UNT Libraries Government Documents Department

The Chelate Process I

Description: The chelate process for the extraction and decontamination of plutonium has been investigated. The process is designed as an alternate process for ihe Hanford type operation. The basic chemical factors have been studied and two flowsheeis have been developed and tested for recovery of plutonium. An over-all yield of plutonium in excess of 99% is reported for one flowsheet using benzene as the organic solvent and 98.5% when toluene was substituted for benzene. The general factors involved in establishing all details of the flowsheets are thoroughly discussed and decontamination studies are indicated to complete the study in the present equipment. (auth)
Date: December 12, 1946
Creator: Thomas, J. R. & Crandall, H. W.
Partner: UNT Libraries Government Documents Department

The Chelate Process, VI. Process flow involving o-dichlorobenzeneas the solvent for TTA

Description: Comparative studies of a series of halogenated solvents, as carriers for TTA in the chelate process for plutonium extraction, indicate that ortho-dichlorobenzene most nearly satisfies the requirements that are set forth. A complete process design is presented for use with this solvent, and flow data and equipment capacities are given for dissolver solution and for uranium-free fission product solution as alternate feeds to the process. Vertical mixer-settlers are recommended as the contractors, although pulsed columns or packed columns are also believed to be suitable. The size of such units is estimated from the best available rate and equilibrium data, and the effects of several operating variable are considered.
Date: January 1, 1951
Creator: Davis Jr., M.W.; Hicks, T.E. & Vermeulen, T.
Partner: UNT Libraries Government Documents Department

Phytosiderophore Effects on Subsurface Actinide Contaminants: Potential for Phytostabilization and Phytoextraction

Description: This project seeks to understand the influence of phytosiderophore-producing plants (grasses, including crops such as wheat and barley) on the biogeochemistry of actinide and other metal contaminants in the subsurface environment, and to determine the potential of phytosiderophore-producing plants for phytostabilization and phytoextraction of actinides and some metal soil contaminants. Phytosiderophores are secreted by graminaceous plants such as barley and wheat for the solubilization, mobilization and uptake of Fe and other essential nutrients from soils. The ability for these phytosiderophores to chelate and absorb actinides using the same uptake system as for Fe is being investigated though characterization of actinide-phytosiderophore complexes (independently of plants), and characterization of plant uptake of such complexes. We may also show possible harm caused by these plants through increased chelation of actinides that increase in actinide mobilization & migration in the subsurface environment. This information can then be directly applied by either removal of harmful plants, or can be used to develop plant-based soil stabilization/remediation technologies. Such technologies could be the low-cost, low risk solution to many DOE actinide contamination problems.
Date: June 1, 2005
Creator: Ruggiero, Christy
Partner: UNT Libraries Government Documents Department

Use of Yb(III) Centered Near Infra-Red (NIR) Luminescence to Determine the Hydration State of a 3,2-HOPO based MRI-Contrast Agent

Description: It has been more than a decade since the first reports of [Gd(Tren-Me-3,2-HOPO)(H{sub 2}O){sub 2}] as a potential new class of magnetic resonance imaging contrast agent (MRI-CA). The defining feature of these 1-methyl-3-hydroxypyridin-2-one (Me-3,2-HOPO) based compounds has been the use of a hexadentate ligand design, and hence an increase in the number of metal bound water molecules, without sacrificing complex stability compared to the typically octadentate contrast agents used commercially. Since that time, significant advances in the properties of these chelates have been steadily reported, including improvements in relaxivity, incorporation into macromolecular architectures and, recently, the first direct verification of solution structure using the discovery of Eu(III) centered luminescence with the isomeric 1-hydroxypyridin-2-one (1,2-HOPO) chelate as a sensitizing chromophore. Nonetheless, it has remained frustrating that direct measurements of the inner sphere hydration state, q, using luminescence techniques with the parent Me-3,2-HOPO compounds have remained elusive, even when direct laser excitation of weakly absorbing f-f transitions were employed (eg. for Eu(III) complexes). This failing can likely be traced to the presence of a low lying LMCT state which efficiently quenches metal based emission. Instead, estimates of the q and hence solution structure have relied on the fitting of relaxivity data to the Solomon-Bloembergen-Morgan equations or, where sufficiently soluble in aqueous solution, studies on the temperature dependence of the paramagnetic contribution to the water {sup 17}O NMR transverse relaxation rate. Recently, Beeby et al reported on a qualitative equation to determine inner sphere hydration based on the change in lifetimes for Yb(III) in going from H{sub 2}O to D{sub 2}O solution, and we reasoned that the lower energy accepting state of Yb(III) may lie below the LMCT state which quenches Eu(III) emission, and hence may facilitate sensitized emission from Yb(III). This hypothesis was borne out experimentally, and herein we describe for the ...
Date: June 9, 2008
Creator: Moore, Evan G.; Seitz, Michael & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department