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Isozymes and In Vivo Activity of Triosephosphate Isomerase

Description: The distribution of isozymes of triosephosphate isomerase was normal in all human tissues examined. This finding argues against the existence of tissue-specific isozymes. Normal distributions of isozymes were also found in patients with cri-du-chat syndrome. Thus it is unlikely that a gene for triosephosphate isomerase is located on the short arm of chromosome five in man. When triosephosphate isomerases from a wide range of species were examined by starch gel electrophoresis, definite evolutionary patterns were found. Kinetic studies were conducted on human triosephosphate isomerase under conditions simulating the intracellular environment of the erythrocyte. Calculations using the kinetic parameters obtained indicate that even in triosephosphate isomerase deficiency disease, enough enzyme activity remains that the rate of glycolysis should not become inhibited.
Date: May 1974
Creator: Snapka, Robert Morris

Ketene Carbodiimide Cycloadditions

Description: It was proposed to study the cycloaddition of ketenes and carbodiimides in some detail. The first objective was to investigate the general applicability of the reaction as a tool for the synthetic organic chemist in the preparation of a new class of substituted β-lactams; i.e., imino-β-lactams. It was proposed for this part of the research problem to look for the intermediate, either directly or indirectly, by trapping experiments. It was further proposed to study substituent effects in the ketene and carbodiimide and also Investigate the effect of solvent polarity on the reaction rate. From these data, it was hoped that the mechanism of the cycloaddition reaction could be elucidated.
Date: August 1970
Creator: Dorsey, Edwin Darrell

Ketene Reactions: I. The Addition of Acid Chlorides to Dimethylketene ; II. The Cycloaddition of Ketenes to Carbonyl Compounds

Description: Part I describes the addition of several acid chlorides to dimethylketene. The resulting 3-ketoacid chlorides were isolated and characterized. Part II describes the cycloaddition of several aldoketenes to chloral. The ketenes were generated in situ by dehydrohalogenation and dehalogenation of appropriately substituted acyl halides.
Date: December 1970
Creator: Smith, Larry

Kinetic Investigation of Atomic Hydrogen with Sulfur-Containing Species

Description: The reactions of atomic hydrogen with methanethiol and that of atomic hydrogen with carbon disulfide were studied experimentally using flash-photolysis resonance-fluorescence techniques. Rate constants were determined over a range of temperatures and pressures, and through analysis and comparison to theoretical work details of the reactions were ascertained.
Date: December 2014
Creator: Kerr, Katherine Elaine

Kinetic Investigation of the Gas Phase Atomic Sulfur and Nitrogen Dioxide Reaction

Description: The kinetics of the reaction of atomic sulfur and nitrogen dioxide have been investigated over the temperature range 298 to 650 K and pressures from 14 - 405 mbar using the laser flash photolysis - resonance fluorescence technique. The overall bimolecular rate expression k (T) = (1.88 ± 0.49) x10-11 exp-(4.14 ± 0.10 kJ mol-1)/RT cm3 molecule-1 s-1 is derived. Ab initio calculations were performed at the CCSD(T)/CBS level of theory and a potential energy surface has been derived. RRKM theory calculations were performed on the system. It is found that an initially formed SNO2 is vibrationally excited and the rate of collisional stabilization is slower than the rate of dissociation to SO + NO products by a factor of 100 - 1000, under the experimental conditions.
Date: May 2011
Creator: Thompson, Kristopher Michael

Kinetic studies and computational modeling of atomic chlorine reactions in the gas phase.

Description: The gas phase reactions of atomic chlorine with hydrogen sulfide, ammonia, benzene, and ethylene are investigated using the laser flash photolysis / resonance fluorescence experimental technique. In addition, the kinetics of the reverse processes for the latter two elementary reactions are also studied experimentally. The absolute rate constants for these processes are measured over a wide range of conditions, and the results offer new accurate information about the reactivity and thermochemistry of these systems. The temperature dependences of these reactions are interpreted via the Arrhenius equation, which yields significantly negative activation energies for the reaction of the chlorine atom and hydrogen sulfide as well as for that between the phenyl radical and hydrogen chloride. Positive activation energies which are smaller than the overall endothermicity are measured for the reactions between atomic chlorine with ammonia and ethylene, which suggests that the reverse processes for these reactions also possess negative activation energies. The enthalpies of formation of the phenyl and β-chlorovinyl are assessed via the third-law method. The stability and reactivity of each reaction system is further rationalized based on potential energy surfaces, computed with high-level ab initio quantum mechanical methods and refined through the inclusion of effects which arise from the special theory of relativity. Large amounts of spin-contamination are found to result in inaccurate computed thermochemistry for the phenyl and ethyl radicals. A reformulation of the computational approach to incorporate spin-restricted reference wavefunctions yields computed thermochemistry in good accord with experiment. The computed potential energy surfaces rationalize the observed negative temperature dependences in terms of a chemical activation mechanism, and the possibility that an energized adduct may contribute to product formation is investigated via RRKM theory.
Date: August 2009
Creator: Alecu, Ionut M.

Kinetic Studies and Vibrational Spectra of Disubstituted Metal Carbonyls

Description: The oxidative elimination reactions of (5-X-phen)Mo(C0)₄ (X = H, CH₃, Cl, NO₂; phen = o-phenanthroline) and (3,4,7,8-(CH₃)₄-phen)Mo(CO)₄ with mercuric chloride in acetone have been investigated. In these reactions, a carbon monoxide group is replaced by two univalent ligands, accompanied by the corresponding increase in coordination number and formal oxidation state of the central metal atom, to give products of the type, (X-phen)Mo(CO)₃(Cl)HgCl. With the exception of (3,4,7,8-(CH₃)₄-phen), the substituted o-phenanthrolines were selected so as to minimize steric differences from one substrate to another while obtaining the widest range of pKₐ of the ligand.
Date: May 1972
Creator: Jernigan, Robert Thorne

Kinetic Studies of Hydroxyl and Hydrogen Atom Reactions

Description: Gas phase kinetics of the reactions involving hydroxyl radical and hydrogen atom were studied using experimental and ab initio theoretical techniques. The rate constant for the H + H2S reaction has been measured from 298 to 598 K by the laser photolysis/resonance fluorescence (LP-RF) technique. The transition state theory (TST) analysis coupled with the measurements support the suggestion that the reaction shows significant curvature in the Arrhenius plot. The LP-RF technique was also used to measure the rate constant of the H + CH3Br reaction over the temperature range 400-813 K. TST and density functional theory (DFT) calculations show that the dominant reaction channel is Br-abstraction. The reaction H + CF2=CF-CF=CF2 was first studied by flash photolysis/resonance fluorescence (FP-RF) method. The experiments of this work revealed distinctly non-Arrhenius behavior, which was interpreted in terms of a change in mechanism. DFT calculations suggest that the adduct is CF2H-CF•-CF=CF2. At lower temperatures a mixture of this molecule and CF2•-CFH-CF=CF2 is likely. The theoretical calculations show that H atom migrates in the fluoroethyl radicals through a bridging intermediate, and the barrier height for this process is lower in the less fluorinated ethyl radical. High level computations were also employed in studies of the rate constants of OH + chloroethylenes reactions. VTST calculations indicate that, except the reaction of OH + C2Cl4, these reactions present a complex behavior. For OH + C2Cl4, conventional TST calculation shows a simple positive temperature-dependence behavior.
Date: May 2002
Creator: Hu, Xiaohua

Kinetic Studies of the Reactions of Alkyl and Silyl Hydrides

Description: The Kinetics of the reactions involving alkyl and silyl hydrides were studied by the flash photolysis / resonance fluorescence technique. The reactions of alkyl radicals (R = C₂H₅, i-C₃H₇, t-C₄H₉) with HBr have been studied at room temperature and the rate constants obtained (units are in cm³ s^-1 ) are: k₃.₃ = (7.01 ± 0.15) x 10^-12, k₃.₂ = (1.25 ± 0.06) x 10^-11, k₃.₁ = (2.67 ± 0.13) x 10^-11 These results, combined with previously determined reverse rate constants and other kinetic information, yield bond dissociation enthalpies (units in kJ mol^-1) at 298 K : primary C-H in C₂H₅-H (423.6 ± 2), secondary C-H in i-C₃H₇-H (409.9 ± 2), tertiary C-H in t-C₄H₉-H (405.1 ± 2). These rate constants and bond energies are in good agreement with previous results.
Date: August 1996
Creator: Yuan, Jessie (Jessie Win-Jae)

Kinetic Studies on C‐h Bond Activation in the Reaction of Triosmium Clusters with Diphosphine and Amidine Ligands

Description: The reaction of 1-(diphenylphosphino)-2-(diphenylphosphito)benzene (PP*) and Os3(CO)10(ACN) has been investigated. A combined experimental and computational study on the isomerization of 1,2-Os3(CO)10[μ-1,2-Ph2P(C6H4)P(OPh)2] (A) and 1,1-Os3(CO)10[μ-1,2-Ph2P(C6H4)P(OPh)2] (B) and reversible ortho-metalation exhibited by the triosmium cluster B are reported. The subsequent conversion of cluster B to the hydrido cluster HOs3(CO)9[μ-1,2-PhP(C6H4-η1)C6H4P(OPh)2] (E) and the benzyne-substituted cluster HOs3(CO)8(µ3-C6H4)[μ-1,2-PhP(C6H4)P(OPh)2] (N) has been established. All of these new clusters have been isolated and fully characterized in solution by IR and NMR spectroscopy; in addition, X-ray diffraction analyses have been performed on the clusters A, B, J, and N. The ortho-metalation reaction that gives cluster E is shown to be reversible, and the mechanism has been probed using selectively deuterated PP* isotopomers. Kinetic and thermodynamic isotope data, in conjunction with DFT calculations, are presented that support the existence of an intermediate unsaturated cluster in the ortho-metalation reaction. Due to interest in the coordination chemistry of formamidines, the non-symmetric amidine ligands PhNC(Me)NHPri, PhNC(Et)NHPri, and (2,4,6-Me3C6H2)NC(Me)NHPri, have been synthesized, and their reaction with Os3(CO)10(MeCN)2 has been investigated. Of the twelve new clusters prepared in section, seven have been structurally characterized by X-ray crystallography.
Date: December 2014
Creator: Yang, Li

Kinetic Study of Ligand Exchange in mu-(2,2,8,8-Tetramethyl-3,7- Dithianonane)-Decacarbonylditungsten(0)

Description: The substitution reaction of (DTN)W2 (CO)10 with P(OCH(CH3 )2 )3 is a stepwise reaction. The kinetics of step 1 follow the equation: -d[substrate] /dt = kld [substrate] + k la [substrate] [ligand]. Thus the mechanism of step 1 is expected to be a competition between dissociative and associative pathways. The kinetics of step 2 follow the equation: -d[(DTN)W(CO)5]/dt = k2dk3[(DTN)W(CO)5][ligand]/k-2[DTN] + k3[ligand] The plot of kobsd versus [ligand] thus is a hyperbolic curve and the plot of 1/kobsd versus 1/[L] exhibits linear behavior. A mechanism for step 2 in which (DTN)W(CO)5 dissociates to an intermediate, W(CO) 5 , and in which DTN and P(OCH(CH3 )2 )3 compete to associate with W(CO) 5 is favored. The dissociative rate constant of the first step, kld' is about 1.2 times of that of the second step, k2d. The dissociation of (DTN)W(CO) 5 from (DTN)W2 (CO) 1 0 is favored over the dissociation of DTN from (DTN)W(CO) 5 due to a combination of the steric, stoichiometric, charge repulsion and entropy effects of the reaction.
Date: May 1982
Creator: Yang, Sang-Nin

Kinetics and Mechanism Study of Diphenylketene Cycloadditions

Description: From a review of the published work in the field of cycloadditions, it is evident that further research is needed to establish the mechanism of ketene cycloadditions. This work was initiated with the intent of obtaining kinetic data which will contribute to the elucidation of the mechanism of ketene cycloadditions.
Date: August 1967
Creator: O'Neal, Hubert Ronald

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)

Kinetics and Mechanisms of Metal Carbonyls

Description: Pulsed laser flash photolysis with both visible and infrared detection has been applied to the study of the displacement of weakly coordinating ligands (Lw) by strongly "trapping" nucleophiles (Ls) containing either an olefinic functionality (Ls = 1-hexene, 1-decene, 1-tetradecene) or nitrogen (Ls = acetonitrile, hydrocinnamonitrile) from the photogenerated 16 electron pentacarbonylchromium (0) intermediate. 5-Chloropent-l-ene (Cl-ol), a potentially bidentate ligand, has been shown to form (ol-Cl) pentacarbonylchromium (0), in which Cl-ol is bonded to Cr via a lone pair on the chlorine, and isomerize to (Cl-ol) pentacarbonylchromium (0), in which Cl-ol is bonded to the olefinic functionality on the submillisecond time scale. This process has been studied in both the infrared and visible region employing both fluorobenzene or n-heptane as the "inert" diluent. Parallel studies employing 1-chlorobutane and 1-hexene were also evaluated and showed great similiarity with the Cl-ol system. The data supported a largely dissociative process with a possibility of a small interchange process involving the H's on the alkyl chain. Studies were also carried out for various Cr(CO)6/arene/Ls systems (arene = various alkyl or halogenated substituted benzenes). The data indicated that for both C6H5R (R=various alkyl chains) or multi-alkyl substituted arenes (i.e. o-xylene, 1,2,3-trimethylbenzene) containing an "unhindered" ring-edge, bonding to the the Cr(CO)5 moiety occurs "edge on" via a partially delocalized center of unsaturation on the ring. The data indicated that both electronic and steric properties of the arenes influence the kinetics, and that an interchange pathway takes place at least, in part, through the alkyl chains on both the arenes and "trapping" nucleophiles. Moreover, halogenated arenes bond through the lone pair on the halogen for both CI- and Br- derivatives but "edge-on" for the fluorinated arenes. Finally, in the case of arene complexes without and "unhindered" ring-edge (i.e., 1,2,3,4,5-pentamethylbenzene) bonding can occur either "edge-on" or through the ring ...
Date: May 1998
Creator: Ladogana, Santino

Kinetics of Reactions of Substituted Group VI B Metal Carbonyls with Phosphites

Description: The problem with which this investigation is concerned is twofold. The initial part of the problem was to prepare a non-sterically demanding bidentate phosphine ligand, 1,2-bis-(Phosphino)ethane, (P-en), and to determine the kinetics of (P-en)Mo(CO)4 with phosphites via spectrophotometric methods in an attempt to determine if steric effects are directing the type of mechanism followed.
Date: August 1972
Creator: Rettenmaier, Albert J.

Kinetics of Sulfur: Experimental Study of the Reaction of Atomic Sulfur with Acetylene and Theoretical Study of the Cn + So Potential Energy Surface

Description: The kinetics of the reaction of atomic sulfur with acetylene (S (3P) + C2H2) were investigated experimentally via the flash photolysis resonance fluorescence method, and the theoretical potential energy surface for the reaction CN + SO was modeled via the density functional and configuration interaction computational methods. Sulfur is of interest in modern chemistry due to its relevance in combustion and atmospheric chemistry, in the Claus process, in soot and diamond-film formation and in astrochemistry. Experimental conditions ranged from 295 – 1015 K and 10 – 400 Torr of argon. Pressure-dependence was shown at all experimental temperatures. The room temperature high-pressure limit second order rate constant was (2.10 ± 0.08) × 10-13 cm3 molecule-1 s-1. The Arrhenius plot of the high-pressure limit rate constants gave an Ea of (11.34 ± 0.03) kJ mol-1 and a pre-exponential factor of (2.14 ± 0.19) × 10-11 cm3 molecule-1 s-1. S (3P) + C2H2 is likely an adduct forming reaction due to pressure-dependence (also supported by a statistical mechanics analysis) which involves intersystem crossing. The potential energy surface for CN + SO was calculated at the B3LYP/6-311G(d) level and refined at the QCISD/6-311G(d) level. The PES was compared to that of the analogous reaction CN + O2. Notable energetically favorable products are NCS + O, CO + NS, and CS + NO. The completed PES will ultimately be modeled at the CCSD(T) level (extrapolated to infinite basis set limit) for theoretical reaction rate analysis (RRKM).
Date: May 2013
Creator: Ayling, Sean A.

Kinetics Studies of Substituted Tungsten Carbonyl Complexes

Description: Thermal reactions and flash photolysis are used to study the olefin bond-migration promoted by tungsten carbonyls. Substitution of piperidine (pip) by 2- allylphenyldiphenylphosphine (adpp) in the cis-(pip)(η^1- adpp)W(CO)-4 complex was investigated, and no olefin bond-migration was observed. This suggests that a vacant coordinated site adjacent to the coordinated olefin is an essential requirement for olefin bond rearrangement. The rates of olefin attack on the photogenerated coordinatively unsaturated species, cis-[(CB)(η^1-ol- P)W(CO)-4] (CB = chlorobenzene, p-ol = Ph-2P(CH-2)-3CH=CH-2; n = 1-4) were measured. Kinetics data obtained both in pure CB and in CB/cyclohexane mixtures support a dissociative mechanism in which the W-CB bond is broken in the transition state. In contrast to results observed in studies of other related systems, no olefin bond-migration is noted. This observation is attributed to P-W coordination at all stages of the reaction, which precludes formation of a reactive intermediate containing a vacant coordination site adjacent to a P-ol bond.
Date: August 1989
Creator: Wang, I-Hsiung, 1950-

Knowledge Discovery of Nanotube Mechanical Properties With an Informatics-Molecular Dynamics Approach

Description: Carbon nanotubes (CNT) have unparalleled mechanical properties, spanning several orders of magnitude over both length and time scales. Computational and experimental results vary greatly, partly due to the multitude of variables. Coupling physics-based molecular dynamics (MD) with informatics methodologies is proposed to navigate the large problem space. The adaptive intermolecular reactive empirical bond order (AIREBO) is used to model short range, long range and torsional interactions. A powerful approach that has not been used to study CNT mechanical properties is the derivation of descriptors and quantitative structure property relationships (QSPRs). For the study of defected single-walled CNTs (SWCNT), two descriptors were identified as critical: the density of non-sp2 hybridized carbons and the density of methyl groups functionalizing the surface. It is believed that both of these descriptors can be experimentally measured, paving the way for closed-loop computational-experimental development. Informatics can facilitate discovery of hidden knowledge. Further evaluation of the critical descriptors selected for Poisson’s ratio lead to the discovery that Poisson’s ratio has strain-varying nonlinear elastic behavior. CNT effectiveness in composites is based both on intrinsic mechanical properties and interfacial load transfer. In double-walled CNTs, inter-wall bonds are surface defects that decrease the intrinsic properties but also improve load transfer. QSPRs can be used to model these inverse effects and pinpoint the optimal amount of inter-wall bonds.
Date: May 2012
Creator: Borders, Tammie L.

Laser Ablation Inductively Coupled Plasma Mass Spectrometry and Raman Spectroscopy Imaging of Biological Tissues

Description: Laser Ablation Inductively coupled plasma mass spectrometry (LA-ICP-MS) and Raman spectroscopy are both powerful imaging techniques. Their applications are numerous and extremely potential in the field of biology. In order to improve upon LA-ICP-MS an in-house built cold cell was developed and its effectiveness studied by imaging Brassica napus seeds. To further apply LA-ICP-MS and Raman imaging to the field of entomology a prong gilled mayfly (Ephemeroptera: Leptophlebiidae) from the Róbalo River, located on Navarino Island in Chile, was studied. Analysis of both samples showcased LA-ICP-MS and Raman spectroscopy as effective instruments for imaging trace elements and larger molecules in biological samples respectively.
Date: May 2016
Creator: Gorishek, Emma

Layered Double Hydroxides and the Origins of Life on Earth

Description: A brief introduction to the current state of research in the Origins of Life field is given in Part I of this work. Part II covers original research performed by the author and co-workers. Layered Double Hydroxide (LDH) systems are anion-exchanging clays that have the general formula M(II)xM(III)(OH)(2x+2)Y, where M(II) and M(III) are any divalent and trivalent metals, respectively. Y can be nearly any anion, although modern naturally occuring LDH systems incorporate carbonate (CO32-), chloride (Cl-), or sulfate (SO42-) anions. Intercalated cobalticyanide anion shows a small yet observable deviation from local Oh symmetry causing small differences between its oriented and non-oriented infrared spectra. Nitroprusside is shown to intercalate into 2:1 Mg:Al LDH with decomposition to form intercalated ferrocyanide and nitrosyl groups of an unidentified nature. The [Ru(CN)6]4- anion is shown to intercalate into layered double hydroxides in the same manner as other hexacyano anions, such as ferrocyanide and cobalticyanide, with its three-fold rotational axis perpendicular to the hydroxide sheets. The square-planar tetracyano-nickelate(II), -palladate(II), and platinate(II) anions were intercalated into both 2:1 and 3:1 Mg:Al layered double hydroxides (LDH). The basal spacings in the 2:1 hosts are approximately 11 Å, indicating that the anions are inclined approximately 75 degrees relative to the hydroxide layers, while in the 3:1 hosts the square-planar anions have enough space to lie more nearly parallel to the LDH cation layers, giving basal spacings of approximately 8 Å. It has been found that the LDH Mg2Al(OH)6Cl catalyzes the self-addition of cyanide, to give in a one-pot reaction at low concentrations an increased yield of diaminomaleonitrile and in addition, at higher ($0.1M) concentrations, a purple-pink material that adheres to the LDH. We are investigating whether this reaction also occurs with hydrotalcite itself, what is the minimum effective concentration of cyanide, and what can be learned about the products ...
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Date: May 2001
Creator: Brister, Brian

Layered Double Hydroxides as Anion- and Cation-Exchanging Materials

Description: Layered double hydroxides (LDH) have been principally known as anion-exchanging, clay-like materials for several decades, and continues to be the main driving force for current and future research. The chemical interactions of LDH, with transition metallocyanides, have been a popular topic of investigation for many years, partly due to the use of powder x-ray diffraction and infrared spectroscopy as the main characterization tools. Each transition metallocyanide has a characteristic infrared stretching frequency that can be easily observed, and their respective sizes can be observed while intercalated within the interlayer of the LDH. The ability of LDH to incorporate metal cations or any ions/molecules/complexes, that have a postive charge, have not been previously investigated, mainly due to the chemical and physical nature of LDH. The possibility of cationic incorporation with LDH would most likely occur by surface adsorption, lattice metal replacement, or by intercalation into the LDH interlayers. Although infrared spectroscopy finds it main use through the identification of the anions incorporated with LDH, it can also be used to study and identify the various active and inactive bending and stretching modes that the metal hydroxide layers have.
Date: May 2007
Creator: Richardson, Mickey Charles

Layered Double Hydroxides: Morphology, Interlayer Anion, and the Origins of Life

Description: The preparation of layered double hydroxides via co-precipitation of a divalent/trivalent metal solution against a base results in 1 mm LDH particles with a disorganized metal lattice. Research was performed to address these morphological issues using techniques such as Ostwald ripening and precipitation via aluminate. Another interesting issue in layered double hydroxide materials is the uptake and orientation of anions into the interlayer. Questions about iron cyanide interlayer anions have been posed. Fourier transform infared spectroscopy and powder x-ray diffraction have been used to investigate these topics. It was found that factors such as orientation, anion charge, and anion structure depended on the divalent/trivalent metal ratio of the hydroxide layer and reactivity time. The cyanide self-addition reaction is an important reaction of classical prebiotic chemistry. This reaction has been shown to give rise to amino acids, purines and pyrimidines. At cyanide concentrations similar to that expected on the early earth, hydrolysis to formamide rather than self-addition occurs. One theory to alleviate this side reaction is the use of minerals or clays that are thought to concentrate and catalyze prebiotics of interest. Layered double hydroxides have been studied as a catalyst for this reaction.
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Date: December 2002
Creator: Halcom-Yarberry, Faith Marie

Layered Double Hydroxides: Synthesis, Characterization, and Interaction of Mg-Al Systems with Intercalated Tetracyanonickelate(II)

Description: The square-planar tetracyanonickelate(II) anion was intercalated into 2:1 and 3:1 Mg-Al layered double hydroxide systems (LDHs). In the 2:1 material, the anion holds itself at an angle of about 30° to the layers, whereas in the 3:1 material it lies more or less parallel to the layers. This is confirmed by orientation effects in the infrared spectra of the intercalated materials and by X-ray diffraction (XRD) data. The measured basal spacings for the intercalated LDH hosts are approximately 11 Å for the 2:1 and approximately 8 Å for the 3:1. The IR of the 2:1 material shows a slight splitting in the ν(CN) peak, which is suppressed in that compound's oriented IR spectrum, indicating that at least some of the intercalated anion's polarization is along the z-axis. This effect is not seen in the 3:1 material. A comparison between chloride LDHs and nitrate LDHs was made with respect to intercalation of tetracyanonickelate(II) anions. Both XRD data and atomic absorption spectroscopy (AAS) data of the LDH tetracyanonickelates confirms that there are no significant differences between the products from the two types of starting materials. The presence of a weak ν(NO) peak in the IR spectra of those samples made from nitrate parents indicates the presence of small amounts of residual [NO3]- in those systems. Small amounts of Cl- present in the chloride-derived samples, while perhaps detectable using AAS, would not be detectable in this manner. An attempted synthesis of Mg-Al LDH carbonates starting from reduced Mg and Al was unsuccessful due to pH constraints on hydroxide solubility in the solvent system used (water). The pH required to precipitate Al(OH)3 in the system was too high to allow precipitation of Mg(OH)2. Consequently, we found it impossible to have both of the required metal hydroxides present simultaneously in the system. An additional synthesis ...
Date: August 2004
Creator: Brister, Fang Wei