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Simultaneously Bound Guests and Chiral Recognition: A Chiral Self-Assembled Supramolecular Host Encapsulates Hydrophobic Guests

Description: Driven by the hydrophobic effect, a water-soluble, chiral, self-assembled supramolecular host is able to encapsulate hydrophobic organic guests in aqueous solution. Small aromatics can be encapsulated in the supramolecular assembly, and the simultaneous encapsulation of multiple guests is observed in many cases. The molecular host assembly is able to recognize different substitutional isomers of disubstituted benzenes with ortho substitution leading to the encapsulation of two guests, but meta or para substitution leading to the encapsulation of only one guest. The scope of hydrophobic guest encapsulation is further explored with chiral natural product guests. Upon encapsulation of chiral guests into the racemic host, diastereomeric host-guest complexes are formed with observed diastereoselectivities of up to 78:22 in the case of fenchone.
Date: March 6, 2008
Creator: Hastings, Courtney J.; Pluth, Michael D.; Biros, Shannon M.; Bergman, Robert G. & Raymond, Kenneth N.
Partner: UNT Libraries Government Documents Department

WATEQF: A FORTRAN IV Version of WATEQ, a Computer Program for Calculating Chemical Equilibrium of Natural Waters

Description: Abstract: WATEQF is a FORTRAN IV computer program that models the thermodynamic speciation of inorganic ions and complex species in solution for a given water analysis. The original version (WATEQ) was written in 1973 by A. H. Truesdell and B. F. Jones in Programming Language/one (PL/1). With but a few exceptions, the thermochemical data, speciation, activity coefficients, and general calculation procedure of WATEQF is identical to the PL/1 version. This report notes the differences between WATEQF and WATEQ, demonstrates how to set up the input data to execute WATEQF, provides a test case for comparison, and makes available a listing of WATEQF.
Date: September 1976
Creator: Plummer, L. Niel; Jones, Blair F, & Truesdell, Alfred H.
Partner: UNT Libraries Government Documents Department

Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous Solution

Description: Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/Tb{sup III} complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in Tb{sup III} complexes that display both large luminescence quantum yield ({phi}) values and strong circularly polarized luminescence (CPL) activities. Both Tb{sup III} complexes are highly emissive, with {phi} values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H{sub 2}O and D{sub 2}O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H{sub 2}O molecule directly bound to the Tb{sup III} ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported Tb{sup III} complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb.
Date: March 15, 2010
Creator: Samuel, Amanda; Lunkley, Jamie; Muller, Gilles & Raymond, Kenneth
Partner: UNT Libraries Government Documents Department

Complexation of NpO2+ with N-methyl-iminodiacetic Acid: in Comparison with Iminodiacetic and Dipicolinic Acids

Description: Complexation of Np(V) with N-methyl-iminodiacetic acid (MIDA) in 1 M NaClO{sub 4} solution was studied with multiple techniques including potentiometry, spectrophotometry, and microcalorimetry. The 1:2 complex, NpO{sub 2}(MIDA){sub 2}{sup 3-} was identified for the first time in aqueous solution. The correlation between its optical absorption properties and symmetry was discussed, in comparison with Np(V) complexes with two structurally related nitrilo-dicarboxylic acids, iminodiacetic acid (IDA) and dipicolinic acid (DPA). The order of the binding strength (DPA > MIDA > IDA) is explained by the difference in the structural and electronic properties of the ligands. In general, the nitrilo-dicarboxylates form stronger complexes with Np(V) than oxy-dicarboxylates due to a much more favorable enthalpy of complexation.
Date: October 1, 2010
Creator: Tian, Guoxin & Rao, Linfeng
Partner: UNT Libraries Government Documents Department

Lactonization and protonation of gluconic acid: a thermodynamicand kinetic study by potentiometry, nmr and esi-ms

Description: In acidic aqueous solutions, gluconate protonation is coupled with lactonization of gluconic acid. With the decrease of pC{sub H}, two lactones ({delta}/{gamma}) are sequentially formed. The {delta}-lactone forms more readily than the {gamma}-lactone. In 0.1 M gluconate solutions, if pC{sub H} is above 2.5, only the {delta}-lactone is generated. When pC{sub H} is decreased below 2.0, the formation of the {gamma}-lactone is observable although the {delta}-lactone predominates. At I = 0.1 M NaClO{sub 4} and room temperature, the deprotonation constant of the carboxylic group, using the NMR technique, was determined to be log K{sub a} = 3.30 {+-} 0.02; the {delta}-lactonization constant, by the batch potentiometric titrations, was obtained to be log K{sub L} = - (0.54 {+-} 0.04). Using ESI-MS, the rate constants of the {delta}-lactonization and the hydrolysis at pC{sub H} {approx} 5.0 were estimated to be k{sub 1} = 3.2 x 10{sup -5} s{sup -1} and k{sup -1} = 1.1 x 10{sup -4} s{sup -1}, respectively.
Date: January 10, 2007
Creator: Zhang, Z.; Gibson, P.; Clark, S.B.; Tian, G.; Zanonato, P. & Rao, L.
Partner: UNT Libraries Government Documents Department

2010 Water & Aqueous Solutions

Description: Water covers more than two thirds of the surface of the Earth and about the same fraction of water forms the total mass of a human body. Since the early days of our civilization water has also been in the focus of technological developments, starting from converting it to wine to more modern achievements. The meeting will focus on recent advances in experimental, theoretical, and computational understanding of the behavior of the most important and fascinating liquid in a variety of situations and applications. The emphasis will be less on water properties per se than on water as a medium in which fundamental dynamic and reactive processes take place. In the following sessions, speakers will discuss the latest breakthroughs in unraveling these processes at the molecular level: Water in Solutions; Water in Motion I and II; Water in Biology I and II; Water in the Environment I and II; Water in Confined Geometries and Water in Discussion (keynote lecture and poster winners presentations).
Date: August 13, 2010
Creator: Ben-Amotz, Dor
Partner: UNT Libraries Government Documents Department

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

Radiolysis of actinides and technetium in alkaline media

Description: The {gamma}-radiolysis of aerated alkaline aqueous solutions of Np(V), Np(VI), Pu(VI), Tc(IV), Tc(V), and TC(VII) was studied in the absence of additives and in the presence of CO{sub 3}{sup 2-}, NO{sub 3}{sup -}, NO{sub 2}{sup -}, EDTA, formate, and other organic compounds. The radiolytic reduction of Np(V), Np(VI), Pu(VI), and TC(VII) under different experimental conditions was examined in detail. The addition of EDTA, formate, and alcohols was found to considerably increase the radiation-chemical reduction yields. The formation of the Np(V) peroxo complex was observed in the {gamma}-radiolysis of alkaline aqueous solutions of Np (VI) in the presence of nitrate.
Date: July 10, 1996
Creator: Delegard, C. H.
Partner: UNT Libraries Government Documents Department


Description: In this work a technique was described to study the repassivation of bare metal surfaces. The advantage of this approach over other techniques is the ease with which multiple repassivation events can be studied. The repassivation rate of aluminum was found to depend on the anion in solution. Repassivation rates are higher for aluminum in phosphate and sulfate solutions compared to borate. It is possible that borate may interact more strongly than sulfate or phosphate on the bare aluminum surface blocking the diffusion of oxygen or changing the rate of repassivation.
Date: September 1, 1977
Partner: UNT Libraries Government Documents Department

Toward a Molecular-Based Understanding of High-Temperature Solvation Phenomena in Aqueous Electrolyte Solutions

Description: The theoretical treatment of the solvation phenomenon of simple ions in aqueous solutions has been rather difficult, despite the apparent simplicity of the system. Long-range solvent-screened electrostatic interactions, coupled to the large variation (with state conditions) of the dielectric permittivity of water, give rise to a variety of rather complex solvation phenomena including dielectric saturation, electrostriction, and ion association. Notably, ion solvation in high-temperature/pressure aqueous solutions plays a leading role in hydrothermal chemistry, such as in the natural formation of ore deposits, the corrosion in boilers and reactors, and in high-temperature microbiology. Tremendous effort has been invested in the study of hydrothermal solutions to determine their thermodynamic, transport, and spectroscopic properties with the goal of elucidating the solute-solvent and solute-solute interactions over a wide range of state conditions. It is precisely at these conditions where our understanding and predictive capabilities are most precarious, in part, as a result of the coexistence of processes with two rather different length scales, i.e., short-ranged (solvation) and long-ranged (compressibility-driven) phenomena (Chialvo and Cummings 1994a). The latter feature makes hydrothermal systems extremely challenging to model, unless we are able to isolate the (compressibility-driven) propagation of the density perturbation from the (solvation-related) finite-density perturbation phenomena (Chialvo and Cummings 1995a).
Date: October 30, 1999
Creator: Chialvo, A. A.; Cummings, P. T.; Kusalik, P. G. & Simonson, J. M.
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


Description: EARLIER investigations have demonstrated that di-cyandiamide (DCDA), the dimer of cyanamide, can successfully promote the dehydration condensation of: (1) glucose and orthophosphate to give glucose-6-phosphate; (2) adenosine and orthophosphate to give adenosine-5'-monophosphate; (3) orthophosphate to give pyrophosphate; (4) alanine to give alanylalanine and alanylalanylalanine. These reactions were carried out in dilute aqueous solutions in the dark. (It was also demonstrated that the combination of ultra-violet light and dicyandiamide could promote the synthesis of dipeptides. This observation has since been confirmed by other investigators.) These experiments were designed to demonstrate one possible means by which such compounds could have been formed on the prebiotic Earth, thus providing materials needed for the origin of living systems. Dicyandiamide itself could have been, present on the primitive Earth as was demonstrated with the ultra-violet irradiation of cyanide solution.
Date: April 1, 1965
Creator: Steinman, Gary; Kenyon, Dean H. & Calvin, Melvin
Partner: UNT Libraries Government Documents Department