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Articles 61 - 90 of 121

Full-Text Articles in Chemistry

Structure Modeling And Property Calculations Of Amorphous Materials, Ilia Ponomarev May 2019

Structure Modeling And Property Calculations Of Amorphous Materials, Ilia Ponomarev

Chemistry & Biochemistry Dissertations - Archive

The demand in discovery of novel materials for a seemingly infinite list of applications is growing year by year. Even though it’s not uncommon to find the application for the material after its discovery upon experimentally studying its properties, it can be essential to be able to build the material to satisfy the specific need. This kind of targeted development for a specific application requires deep understanding of the “synthesis => structure => properties” sequence, and this is why insights into the mechanisms of the synthesis, structure formation and structure vs. properties relations are highly desired. Structural insights can be …


Interactions Of (My) 6 (M = Zn, Cd; Y = O, S, Se) Quantum Dots With N-Bases, Mariusz Michalczyk, Wiktor Zierkiewicz, Steve Scheiner Apr 2019

Interactions Of (My) 6 (M = Zn, Cd; Y = O, S, Se) Quantum Dots With N-Bases, Mariusz Michalczyk, Wiktor Zierkiewicz, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

(MY)6 clusters, with M = Zn and Cd and Y = O, S, Se, form double-layer drum-like structures containing M–Y covalent bonds. The positive regions near the M atoms attract the N atom of both NH3 and NMe3 so as to form a noncovalent M···N bond. This bond is quite strong, with interaction energies exceeding 35 kcal/mol. The bond strength diminishes with reduced electronegativity of the Y atom (O > S > Se) and is stronger for M = Zn than for Cd. Trimethylation of the base enhances the bond strength. The interaction is dominated by the electrostatic component …


Palladium-Catalyzed Direct Α‑C(Sp3) Heteroarylation Of Ketones Under Microwave Irradiation, Andrew Quillen, Quynh Nguyen, Matthew Neiser, Kara Lindsay, Alexander Rosen, Stephen Ramirez, Stefana Costan, Oscar Rodriguez, Diego Rivera, Abdurrahman Atesin, Tülay A. Ateşin Apr 2019

Palladium-Catalyzed Direct Α‑C(Sp3) Heteroarylation Of Ketones Under Microwave Irradiation, Andrew Quillen, Quynh Nguyen, Matthew Neiser, Kara Lindsay, Alexander Rosen, Stephen Ramirez, Stefana Costan, Oscar Rodriguez, Diego Rivera, Abdurrahman Atesin, Tülay A. Ateşin

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

Heteroaryl compounds are valuable building blocks in medicinal chemistry and chemical industry. A palladium-catalyzed direct α-C(sp3) heteroarylation of ketones under microwave irradiation is developed and reported in this study. Under optimized conditions, twenty-eight (28) heteroarylated ketones were prepared in this study to demonstrate the substrate scope of this reaction. The ground-state optimized structure of Pd(0) active catalyst with 2-dicyclohexylphosphino-2′,4′,6′-triisopropylbiphenyl (XPhos) in toluene, and the products of its reaction with 3-bromopyridine and acetophenone were studied using all-atom density functional theory. This study provided insightful information for palladium catalytic system design to generate heteroaryl compounds.


A Theoretical Investigation On The Activation Of Small Molecules By A Disilenide: A Dft Prediction, Cem Burak Yildiz, Akin Azi̇zoğlu Jan 2019

A Theoretical Investigation On The Activation Of Small Molecules By A Disilenide: A Dft Prediction, Cem Burak Yildiz, Akin Azi̇zoğlu

Turkish Journal of Chemistry

Herein, we proposed several mechanistic scenarios for activation of small molecules (NH$_{3}$, CO$_{2}$, CS$_{2}$, H$_{2}$, CH$_{4}$, N$_{2}$, and N$_{2}$O) by a disilicon analogue of a vinyl anion (1H) using density functional theory (DFT) calculations. The DFT results established that all the possible reactions to yield a variety of potential products have an exergonic nature except for the activation of N$_{2}$ with the obtained overall energy of $\Delta $G = 33.6 kcal mol$^{-1}$. Moreover, the highest exergonic character was $\Delta $G = $-$95.8 kcal mol$^{-1}$ for N$_{2}$O. Therefore, the findings reveal that 1H can be considered a suitable candidate for activation …


Investigation Of Solvation And Solvent Coordination Effects In Iron Porphyrin Nitrosyls By Infrared Spectroelectrochemistry And Dft Calculations, Md. Hafizur Rahman, Michael D. Ryan Jan 2019

Investigation Of Solvation And Solvent Coordination Effects In Iron Porphyrin Nitrosyls By Infrared Spectroelectrochemistry And Dft Calculations, Md. Hafizur Rahman, Michael D. Ryan

Chemistry Faculty Research and Publications

Visible and infrared spectroelectrochemistry of Fe(OEPone)(NO) (H2OEPone = octaethylporphinone) were examined in methylene chloride and THF. The visible spectra of Fe(OEPone)(NO) were similar in both solvents. Unlike other ferrous porphyrin nitrosyls, a six-coordinate complex was formed with THF as a ligand. This led to two nitrosyl bands in the infrared spectrum. The absorbance of these bands depended on the concentration of THF in the solution. Solvation and coordination effects on the carbonyl and nitrosyl bands were observed for both the nitrosyl and reduced-nitrosyl complexes. DFT calculations were carried out to interpret the spectral changes.


Dft-Assisted Design And Evaluation Of Bifunctional Amine/Pyridine-Oxazoline Metal Catalysts For Additions Of Ketones To Unactivated Alkenes And Alkynes, Eric Greve, Jacob D. Porter, Chris Dockendorff Oct 2018

Dft-Assisted Design And Evaluation Of Bifunctional Amine/Pyridine-Oxazoline Metal Catalysts For Additions Of Ketones To Unactivated Alkenes And Alkynes, Eric Greve, Jacob D. Porter, Chris Dockendorff

Chemistry Faculty Research and Publications

Bifunctional catalyst systems for the direct addition of ­ketones to unactivated alkenes/alkynes were designed and modeled by density functional theory (DFT). The designed catalysts possess bidentate ligands suitable for binding of pi-acidic group 10 metals capable of activating alkenes/alkynes, and a tethered organocatalyst amine to ­activate the ketone via formation of a nucleophilic enamine intermediate. The structures of the designed catalysts before and after C–C bond formation were optimized using DFT, and reaction steps involving group 10 metals were predicted to be significantly exergonic. A novel oxazoline precatalyst with a tethered amine separated by a meta-substituted benzene spacer was synthesized …


Dft-Assisted Design And Evaluation Of Bifunctional Copper(I) Catalysts For The Direct Intermolecular Addition Of Aldehydes And Ketones To Alkynes, Jacob D. Porter, Eric Greve, Abdulmohsen Alsafran, Adam R. Benoit, Sergey V. Lindeman, Chris Dockendorff Sep 2018

Dft-Assisted Design And Evaluation Of Bifunctional Copper(I) Catalysts For The Direct Intermolecular Addition Of Aldehydes And Ketones To Alkynes, Jacob D. Porter, Eric Greve, Abdulmohsen Alsafran, Adam R. Benoit, Sergey V. Lindeman, Chris Dockendorff

Chemistry Faculty Research and Publications

Bifunctional catalysts containing discrete metal pi-acid and amine sites were designed and investigated for the direct intermolecular addition of aldehydes and ketones to unactivated alkynes. Copper(I)-based catalysts were prioritized based on intramolecular (Conia-ene type) reactions, and complexes were designed with tridentate ligands and potentially hemilabile heterocyclic spacers. The structures of the designed catalysts were computed using density functional theory (DFT), and the relative energies of putative catalytic intermediates were estimated and used to prioritize catalyst designs. Novel bifunctional precatalysts containing a thiazole spacer were synthesized via a 9-step sequence and combined with transition metals before screening for the direct addition …


Conformational Analysis Of A Taddol-Based Phosphoramidite P,N Ligand In A Palladium(Ii) Η3-Π-Allyl Complex, Tülay A. Ateşin, Abdurrahman Atesin, Oscar Rodriguez, Diego Rivera, Lohany Y. Garcia Sep 2018

Conformational Analysis Of A Taddol-Based Phosphoramidite P,N Ligand In A Palladium(Ii) Η3-Π-Allyl Complex, Tülay A. Ateşin, Abdurrahman Atesin, Oscar Rodriguez, Diego Rivera, Lohany Y. Garcia

School of Integrative Biological & Chemical Sciences (Formerly Dept. of Chemistry)

Highlights

  • Two lowest energy conformers differ in allyl conformation, conformer with exo allyl having lower energy.
  • Lowest energy conformer has “chair” conformation of 7-membered ring and “edge-on/face-on/face-on/edge-on” array of pH groups.
  • Next lowest energy conformer with exo allyl has alternating “edge-on/face-on” arrangement and “twist” 7-membered ring.
  • Changes in “chair/twist” conformations with different substrates is possible due to 2.4 kcal/mol energy difference.
  • These results explain stereochemical outcome of the reaction, and will guide design of new catalysts.

Abstract

The most stable conformations of a TADDOL-based phosphoramidite P,N ligand coordinated to a palladium(II) η3-π-allyl fragment have been investigated using …


Regium Bonds Between Mn Clusters (M=Cu,Ag,Au And N=2-6) And Nucleophiles Nh3 And Hcn, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner Aug 2018

Regium Bonds Between Mn Clusters (M=Cu,Ag,Au And N=2-6) And Nucleophiles Nh3 And Hcn, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The most stable geometries of the coinagemetal (or regium) atom (Cu, Ag, Au) clusters Mn for n up to 6 are all planar, and adopt the lowest possible spin multiplicity. Clusters with even numbers of M atoms are thus singlets, while those with odd n are open-shell doublets. Examination of the molecular electrostatic potential (MEP) of each cluster provides strong indications of the most likely site of attack by an approaching nucleophile, generally one of two positions. A nucleophile (NH3 or HCN) most favorably approaches one particular M atom of each cluster, rather than a bond midpoint or face. In …


Nmr Spectroscopic Properties Of Nucleotides, And A New Method Of Numeric Calculation Of Raman Intensities For Organic Molecules, William R. Ehrhardt Aug 2018

Nmr Spectroscopic Properties Of Nucleotides, And A New Method Of Numeric Calculation Of Raman Intensities For Organic Molecules, William R. Ehrhardt

Graduate Theses/Dissertations

General and accurate computational methodologies are currently lacking for large chemical systems. This is primarily due to the computational expense required to perform calculations on systems with one hundred or more atoms. Calculated spectroscopic properties could aid in the process of elucidating structural features of large biologically relevant molecules if accurate and inexpensive methods are developed. Towards this end the first steps were taken to design a general methodology for predicting NMR chemical shifts of large nucleic acid systems. It was found that HF and semi-empirical methods were not sufficient for optimization of nucleobases, and therefore larger nucleotide or nucleic …


Comparison Between Tetrel Bonded Complexes Stabilized By Σ And Π Hole Interactions, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner Jun 2018

Comparison Between Tetrel Bonded Complexes Stabilized By Σ And Π Hole Interactions, Wiktor Zierkiewicz, Mariusz Michalczyk, Steve Scheiner

Chemistry and Biochemistry Faculty Publications

The σ-hole tetrel bonds formed by a tetravalent molecule are compared with those involving a π-hole above the tetrel atom in a trivalent bonding situation. The former are modeled by TH4, TH3F, and TH2F2 (T = Si, Ge, Sn) and the latter by TH2=CH2, THF=CH2, and TF2=CH2, all paired with NH3 as Lewis base. The latter π-bonded complexes are considerably more strongly bound, despite the near equivalence of the σ and π-hole intensities. The larger binding energies of the π-dimers are attributed to greater electrostatic attraction and orbital interaction. Each progressive replacement of H by F increases the strength of …


Computational Modeling Of Electronically Excited States In Cobalamin-Dependent Reactions., Brady D. Garabato May 2018

Computational Modeling Of Electronically Excited States In Cobalamin-Dependent Reactions., Brady D. Garabato

Electronic Theses and Dissertations

The current understanding of the photolytic properties of Vitamin B12 derivatives or cobalamins are summarized from a computational point of view. The focus is on two non-alkylcobalamins, cyanocobalamin (CNCbl) and hydroxocobalamin (HOCbl), two alkylcobalamins, methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), as well as the stable cob(II)alamin radical. Photolysis of alkylcobalamins involves low-lying singlet excited states where photo-dissociation of the Co-C bond forms singlet-born alkyl/cob(II)alamin radical pairs (RPs). Potential energy surfaces (PESs) of low-lying excited states as functions of both axial bonds provide the most reliable tool for analysis of photochemical and photophysical properties. Due to the size limitations associated with the …


Computational Study Of Lawesson’S Reagent Mediated Fluorenone Dimerization Forming 9,9’-Bifluorenylidene, Andrew Jourdan Eckelmann May 2018

Computational Study Of Lawesson’S Reagent Mediated Fluorenone Dimerization Forming 9,9’-Bifluorenylidene, Andrew Jourdan Eckelmann

Graduate Theses/Dissertations

The ambition of this work is to start a path to the a priori rational design of high yield production for electron acceptors with finely tuned band gaps, from the comfort of an armchair. To this end, organic photovoltaics offer a cheap and sustainable means of manufacture using readily available materials and avoids the toxicity of some of the heavy metals used in first and second-generation solar cells such as cadmium. The microwave assisted Lawesson’s reagent mediated one-pot one-step solventless synthesis takes less than 3 minutes and results in an 84% yield of 9,9’-bifluorenylidene from two equivalents of fluorenone. While …


Characterization Of Polymers Containing Ferrocene And Imidazole With Density Functional Theory, Eric Mullins Apr 2018

Characterization Of Polymers Containing Ferrocene And Imidazole With Density Functional Theory, Eric Mullins

Electronic Theses & Dissertations

Electrochemical and UV-Vis studies on these polymers in the presence of aqueous solutions containing metal ions have revealed significant modifications in the electrochemical properties and absorption spectra. These modifications in electrochemical properties could be attributed to the ability of the imidazole to coordinate with metal ions, increasing its electron deficiency and enhancing oxidization of the nearby ferrocene moiety if it is in close proximity with imidazole. However, the mechanism of interaction between the imidazole and metal ions, as well as the equilibrium geometry of the resulting polymer-metal ion complex is unknown.

In this thesis, density functional theory (DFT) was used …


Progress Toward Synthetically Simplified Natural Anticancer Peptide, David W. Kastner, Steven L. Castle Mar 2018

Progress Toward Synthetically Simplified Natural Anticancer Peptide, David W. Kastner, Steven L. Castle

Library/Life Sciences Undergraduate Poster Competition 2018

Yaku’amide A was isolated in late 2010 from the deep-sea sponge Ceratopsion sp. and exhibits potent inhibitory activity against 39 human cancer cell lines via a potentially novel mode of action. However, the total synthesis requires many steps and produces low yields. In this study, we determined two simpler YA analogues that may retain its anticancer properties and can be synthesized in larger quantities. The analogues replace dehydroisoleucine with either dehydroethylnorvaline or dehydrovaline.


Adsorption Of Tnt, Dnan, Nto, Fox7, And Nq Onto Cellulose, Chitin, And Cellulose Triacetate. Insights From Density Functional Theory Calculations, Guido Todde, Sanjiv K. Jha, Gopinath Subramanian, Manoj K. Shula Feb 2018

Adsorption Of Tnt, Dnan, Nto, Fox7, And Nq Onto Cellulose, Chitin, And Cellulose Triacetate. Insights From Density Functional Theory Calculations, Guido Todde, Sanjiv K. Jha, Gopinath Subramanian, Manoj K. Shula

Faculty Publications

Insensitive munitions (IM) compounds such as DNAN (2,4-dinitroanisole), NTO (3-nitro-1,2,4-triazol-5-one), NQ (nitroguanidine), and FOX7 (1,1-diamino-2,2-dinitroethene) reduce the risk of accidental explosions due to shock and high temperature exposure. These compounds are being used as replacements for sensitive munition compounds such as TNT (2,4,6-trinitromethylbenzene) and RDX (1,3,5-hexahydro-1,3,5-trinitro-1,3,5-triazine). NTO and NQ in IM compounds are more soluble than TNT or RDX, hence they can easily spread in the environment and get dissolved if exposed to precipitation. DNAN solubility is comparable to TNT solubility. Cellulosic biomass, due to its abundance in the environment and its chemical structure, has a high probability of adsorbing …


Catalyst Design And Mechanism Study With Computational Method For Small Molecule Activation, Muqiong Liu Jan 2018

Catalyst Design And Mechanism Study With Computational Method For Small Molecule Activation, Muqiong Liu

Electronic Theses and Dissertations

Computational chemistry is a branch of modern chemistry that utilizes the computers to solve chemical problems. The fundamental of computational chemistry is Schrödinger equation. To solve the equation, researchers developed many methods based on BornOppenheimer Approximation, such as Hartree-Fock method and DFT method, etc. Computational chemistry is now widely used on reaction mechanism study and new chemical designing. In the first project described in Chapter 3, we designed phosphine oxide modified Ag3, Au3 and Cu3 nanocluster catalysts with DFT method. We found that these catalysts were able to catalyze the activation of H2 by cleaving the H-H bond asymmetrically. The …


Physicochemical, Spectroscopic Properties, And Diffusion Mechanisms Of Small Hydrocarbon Molecules In Mof-74-Mg/Zn: A Quantum Chemical Investigation, Gemechis Degaga Jan 2018

Physicochemical, Spectroscopic Properties, And Diffusion Mechanisms Of Small Hydrocarbon Molecules In Mof-74-Mg/Zn: A Quantum Chemical Investigation, Gemechis Degaga

Dissertations, Master's Theses and Master's Reports

In petroleum refining industries, the fracturing process allows for the cracking of long-chain hydrocarbons into a mixture of small olefin and paraffin molecules that are then separated via the energetically and monetarily demanding cryogenic distillation process. In an attempt to mitigate both energetic and capital consumptions, selective sorption of light hydrocarbons by tunable sorbents, such as metal-organic frameworks (MOFs), appears to be the most promising alternative for a more efficient gas separation process. MOFs are novel porous materials assembled from inorganic bricks connected by organic linkers. From a crystal engineering stand point, MOFs are advantageous in creating a range …


Structure And Property Calculations Of Amorphous Ceramics And Glasses Using Density Functional Theory Calculations And Empirical Potential Molecular Dynamic Simulations, Atreyi Dasmahapatra Dec 2017

Structure And Property Calculations Of Amorphous Ceramics And Glasses Using Density Functional Theory Calculations And Empirical Potential Molecular Dynamic Simulations, Atreyi Dasmahapatra

Chemistry & Biochemistry Dissertations - Archive

The work in this thesis involves modeling amorphous ceramics and glasses using the tools of DFT and classical MD. Systems investigated include: metal-silicate glasses (in particular HfO2- SiO2), composite coatings (comprising of Zr-Si-B-C-N), and the refractory materials amorphous silicon nitride (a-Si3N4) and amorphous silicon boron nitride (a-SiBN). Modeling techniques include traditional “melt-and-quench” simulations combined with simulated annealing. Structures are further investigated for their physical and chemical properties. A brief overview of each chapter is given below: Hafnia-silica glasses (HfO2-SiO2) find applications in microelectronics and optical waveguides. I did a computational study of the thermochemistry of these compounds exploring enthalpy of …


Electronic Structure Evaluation Of Competing Pathways In The Gold(Iii)-Catalyzed Ohloff-Rautenstrauch Cyclosimerization Converting Propargylic Acetates To Carene-Like Natural Products, Jeremy M. Hines Aug 2017

Electronic Structure Evaluation Of Competing Pathways In The Gold(Iii)-Catalyzed Ohloff-Rautenstrauch Cyclosimerization Converting Propargylic Acetates To Carene-Like Natural Products, Jeremy M. Hines

Graduate Theses/Dissertations

Propargylic acetates can lead to complex transformations upon exposure to a gold catalyst. Gold catalyzed transformations also allow for simple synthesis of a number of natural products. Gold (III)-cycloisomerization of a 5-acetoxy-1,6-enyne is reported to proceed through two pathways that differ in the order of major events: cyclization followed by ester migration (“cyclization first”) or the reverse (“migration first”). Both pathways could theoretically proceed in either order. This rearrangement is called the Ohloff-Rautenstrauch rearrangement and has high regio- and stereocontrol affording a bicylo[4.1.0]heptane carbon substructure. This rearrangement allows for the synthesis of the carene class of natural products. Computational modeling …


Application Of Dft-Derived Relationships Between Chemical Environment And ²⁹Si Nuclear Magnetic Resonance Spectroscopy To Determine Structure In Silicon Oxycarbide Ceramics, John Paul Nimmo May 2017

Application Of Dft-Derived Relationships Between Chemical Environment And ²⁹Si Nuclear Magnetic Resonance Spectroscopy To Determine Structure In Silicon Oxycarbide Ceramics, John Paul Nimmo

Chemistry & Biochemistry Theses - Archive

Silicon oxycarbide (SiCO) is an amorphous ceramic material widely used in industrial applications, for its useful electronic and biologically-compatible properties.1-3 SiCO is resistant to crystallization, remaining amorphous even above temperatures at which amorphous SiO2 would crystallize. Though silica (SiO2¬) and silicon carbide (SiC) are almost immiscible, it is useful to consider the material as a phase composition of these along with carbon, according to the formula below. The first two terms in braces can be considered as being the “SiCO glass” into which a third term representing excess or “free” carbon is incorporated as graphite-like nano-flakes and bands. SiC_x O_y={y/2 …


Homogeneous Ligand-Centered Hydrogen Evolution And Hydrogen Oxidation : Exploiting Redox Non-Innocence To Drive Catalysis., Andrew Z. Haddad May 2017

Homogeneous Ligand-Centered Hydrogen Evolution And Hydrogen Oxidation : Exploiting Redox Non-Innocence To Drive Catalysis., Andrew Z. Haddad

Electronic Theses and Dissertations

Hydrogen is a promising carbon-free fuel / energy carrier and is an essential building block for many industrial and agricultural processes. Rising energy demands have ignited interest in the development of carbon-free and carbon neutral energy sources. In this context, hydrogen is an attractive candidate—being energy-dense, carbon-free—and easily accessible through a two-electron reduction of water. Accordingly, many electrochemical homogeneous catalyst systems have been studied, with a focus on understanding the mechanism of hydrogen evolution proceeding through metal-hydride intermediates. However, there has been a renaissance in hydrogen evolution reaction (HER) catalyst design, with many groups implicating ligand redox non-innocence as a …


Computational Quantum Chemistry Studies Of The Stabilities Of Radical Intermediates Formed During The Oxidation Of Melatonin, Constance E. Warden Dec 2016

Computational Quantum Chemistry Studies Of The Stabilities Of Radical Intermediates Formed During The Oxidation Of Melatonin, Constance E. Warden

Electronic Theses and Dissertations

Melatonin, a nontoxic natural antioxidant, is of interest as a possible spin trap for use in spectroscopic methods to observe and identify short-lived free radicals, which have been linked to oxidative stress that may result in serious health problems. However, the reaction mechanisms for the oxidation of melatonin to form the product N1-acetyl-N2-formyl-5-methoxykynuramine are still not well understood. Computational quantum chemistry studies have been done on four proposed reaction mechanisms, involving the following major intermediate structures: a dioxetane, an epoxide, a melatonin radical cation, and a spin radical adduct. Molecular geometries were optimized at the …


Computational Studies On Mechanisms And Reactivity Of Mercury And Cobalt Organometallic Reactions, Jack Terrell Fuller Jul 2016

Computational Studies On Mechanisms And Reactivity Of Mercury And Cobalt Organometallic Reactions, Jack Terrell Fuller

Theses and Dissertations

Density Functional Theory (DFT) is a powerful tool for treating large organometallic structures efficiently and accurately. DFT calculations on the Hg-catalyzed oxidation of methane to methyl bisulfate in sulfuric acid suggest the lowest energy pathway involves a closed-shell electrophilic C–H activation mechanism coupled with metal alkyl reductive functionalization and oxidation by SO3. Comparison to Tl, Zn, and Cd suggests that Hg is unique in its ability to catalyze this set of reaction steps. Comparison to K2S2O8 highlights the selectivity of this C–H activation reaction as opposed to radical conditions. In contrast, DFT calculations indicate that CoIII(TFA)3 oxidizes methane through a …


Segmentation And Additive Approach: A Reliable Technique To Study Noncovalent Interactions Of Large Molecules At The Surface Of Single‐Wall Carbon Nanotubes, Ana M. Torres, Steve Scheiner, Ajit K. Roy, Andrés M. Garay-Tapia, John J. Bustamante, Tapas Kar May 2016

Segmentation And Additive Approach: A Reliable Technique To Study Noncovalent Interactions Of Large Molecules At The Surface Of Single‐Wall Carbon Nanotubes, Ana M. Torres, Steve Scheiner, Ajit K. Roy, Andrés M. Garay-Tapia, John J. Bustamante, Tapas Kar

Chemistry and Biochemistry Faculty Publications

This investigation explores a new protocol, named Segmentation and Additive approach (SAA), to study exohedral noncovalent functionalization of single-walled carbon nanotubes (SWNTs) with large molecules, such as polymers, bio-molecules etc, by segmenting the entire system into smaller units to reduce computational cost. A key criterion of the segmentation process is the preservation of the molecular structure responsible for stabilization of the entire system in smaller segments. Noncovalent interaction of linoleic acid (LA, C18H32O2), a fatty acid, at the surface of a (10,0) zigzag nanotubeis considered for test purposes. Three smaller segmented models have been created from the full (10,0)-LA system …


Optimizing Protocols For Carbohydrate Nmr Chemical Shift Computations, Michael Trent Kemp Mar 2016

Optimizing Protocols For Carbohydrate Nmr Chemical Shift Computations, Michael Trent Kemp

USF Tampa Graduate Theses and Dissertations

The spectroscopic analysis of cellulose is experimentally challenging while computationally accessible with recent developments in NMR code. However, prior to using density functional theory to calculate the NMR chemical shifts of cellulose, smaller, sugar-like molecule systems need to be benchmarked against experimental values. The quantum mechanical / molecular mechanical (QM/MM) calculations presented herein utilize six test systems: ethanol, pyridine, pyrrolidine, pyrrole, myo-inositol and scyllo-inositol in conjunction with the reference tetramethylsilane used to scale the calculated isotropic shielding tensors to relative chemical shifts. The effect of solvent on calculated NMR chemical shifts has also been investigated with regard to quantity of …


Density Functional Study Of The Structure And Water Adsorption Activity Of An Al$_{30}$O$_{30}$ Star-Shaped Alumina Nanocage, Mehdi Zamani Jan 2016

Density Functional Study Of The Structure And Water Adsorption Activity Of An Al$_{30}$O$_{30}$ Star-Shaped Alumina Nanocage, Mehdi Zamani

Turkish Journal of Chemistry

Molecular and electronic structures of a novel Al$_{30}$O$_{30}$ star-shaped alumina nanocage (SANC) were studied using the recently developed CAM-B3LYP density functional method. Comparison of the stretching vibrational modes of this compound with the corresponding modes related to an Al$_{20}$O$_{30}$ perfect cage and Al$_{50}$O$_{75}$ tubular alumina nanomaterials showed a shift to lower frequencies, while the bending modes moved to higher frequencies. The highest occupied molecular orbital (HOMO) of the SANC had 65% nonbonding character, whereas the lowest unoccupied molecular orbital (LUMO) was 72% antibonding. The HOMO and LUMO of the SANC arose mostly from Al 3s and 2p atomic orbitals. The …


Experimental And Theoretical Investigation Of The Reaction Between Co$_{2}$ And Carbon Dioxide Binding Organic Liquids, Hi̇lal Tankal, Özge Yüksel Orhan, Erdoğan Alper, Telhat Özdoğan, Hakan Kayi Jan 2016

Experimental And Theoretical Investigation Of The Reaction Between Co$_{2}$ And Carbon Dioxide Binding Organic Liquids, Hi̇lal Tankal, Özge Yüksel Orhan, Erdoğan Alper, Telhat Özdoğan, Hakan Kayi

Turkish Journal of Chemistry

The reaction kinetics of CO$_{2}$ absorption into new carbon dioxide binding organic liquids (CO$_{2}$BOLs) was comprehensively studied to evaluate their potential for CO$_{2}$ removal. A stopped-flow apparatus with conductivity detection was used to determine the CO$_{2}$ absorption kinetics of novel CO$_{2}$BOLs composed of DBN (1,5-diazabicyclo[4.3.0]non-5-ene)/1-propanol and TBD (1,5,7-triazabicyclo[4.4.0]dec-5-ene)/1-butanol. A modified termolecular reaction mechanism for the reaction of CO$_{2}$ with CO$_{2}$BOLs was used to calculate the observed pseudo-first-order rate constant k$_{0}$ (s$^{-1})$ and second-order reaction rate constant k$_{2}$ (m$^{3}$/kmol.s). Experiments were performed by varying organic base (DBN or TBD) weight percentage in alcohol medium for a temperature range of 288-308 K. …


From Dye Sensitized Solar Cells To Organic Field Effect Transistors: A Computational Investigation Into The Structural And Electronic Properties Of Novel Phthalocyanines, Patrick J. Dwyer Dec 2015

From Dye Sensitized Solar Cells To Organic Field Effect Transistors: A Computational Investigation Into The Structural And Electronic Properties Of Novel Phthalocyanines, Patrick J. Dwyer

Seton Hall University Dissertations and Theses (ETDs)

Phthalocyanines (Pc) have gained intense research attention in many diverse application areas due to their highly tunable electronic and structural properties through modification of the molecular periphery and metal center. Throughout this work a series of novel perfluoro-isopropyl substituted MPc have been investigated through theoretical methods. First, the synthetic mechanisms of these Pcs will be explored to gain insight into the experimentally observed Pc product distribution. By examining the electronic structure and formation energies of the various Pc precursors, we explain the product distribution as well as propose the formation of additional Pcs, which were not currently believed to form. …


Computational Studies On Bimetallic Catalysis And X-Ray Absorption Spectroscopy, Sayakkarage R. G. Fernando Jan 2015

Computational Studies On Bimetallic Catalysis And X-Ray Absorption Spectroscopy, Sayakkarage R. G. Fernando

LSU Doctoral Dissertations

Computational studies are very important to gain an insight into reaction mechanisms and in interpreting and understanding complicated experimental observations. This report contains a discussion on computational studies performed on bimetallic catalysis and on X-ray absorption spectroscopy of insulators. The viability of a bimetallic rhodium and cobalt catalysts for industrially important hydroformylation and aldehyde-water shift catalysis (AWS) is discussed. Density functional theory (DFT) studies were used for bimetallic catalysis and time-dependent DFT studies were used for excited state dynamics. These studies were performed using Gaussian 09 package and NWChem. Hydroformylation is experimentally performed in acetone and 30% water/acetone systems and …