Chemistry Commons^™

Flavin-N5 Covalent Intermediate In A Nonredox Dehalogenation Reaction Catalyzed By An Atypical Flavoenzyme, Yumin Dai, Karina Kizjakina, Ashley C. Campbell, David A. Korasick, John J. Tanner, Pablo Sobrado

Chemistry Faculty Research & Creative Works

The flavin-dependent enzyme 2-haloacrylate hydratase (2-HAH) catalyzes the conversion of 2-chloroacrylate, a major component in the manufacture of acrylic polymers, to pyruvate. The enzyme was expressed in Escherichia coli, purified, and characterized. 2-HAH was shown to be monomeric in solution and contained a non-covalent, yet tightly bound, flavin adenine dinucleotide (FAD). Although the catalyzed reaction was redox-neutral, 2-HAH was active only in the reduced state. A covalent flavin-substrate intermediate, consistent with the flavin-acrylate iminium ion, was trapped with cyanoborohydride and characterized by mass spectrometry. Small-angle X-ray scattering was consistent with 2-HAH belonging to the succinate dehydrogenase/fumarate reductase family of flavoproteins. …

Ab Initio Structural Studies Of Cyclobutylmethyl Cations: Effect Of Fluoroalkyl Groups On The Relative Stability Of The Carbocations, Prakash Reddy, Golam Rasul, G. K. Surya Prakash

Chemistry Faculty Research & Creative Works

Ab initio calculations at MP2/cc-pVTZ level show that the trifluoromethyl group has a strong destabilizing effect on the nonclassical, σ-bridged cyclobutylmethyl cations. The GIAO-MP2 derived ¹³C NMR chemical shifts indicate substantial charge delocalization from the neighboring cyclobutyl ring for carbocations with an α-fluorolkyl group as compared to the 1-cyclobutylethyl cation, and this enhanced charge delocalization in case of the α-(trifluoromethyl)cyclobutylmethyl cation would lead to the ring-opening rearrangement to form the relatively more stable nonclassical primary cyclobutylmethyl cation, in which the carbocation center is farthest from the strongly electron-withdrawing trifluoromethyl group.

Identification Of Aspergillus Fumigatus Udp-Galactopyranose Mutase Inhibitors, Julia S.Martin Del Campo, Meital Eckshtain-Levi, Nancy J. Vogelaar, Pablo Sobrado

Chemistry Faculty Research & Creative Works

Aspergillus fumigatus is an opportunistic human pathogen responsible for deadly, invasive infections in immunocompromised patients. The A. fumigatus cell wall is a complex network of polysaccharides among them galactofuran, which is absent in humans. UDP-galactopyranose mutase (UGM) catalyzes the conversion of UDP-galactofuranose (UDP-Galf) to UDP-galactopyranose (UDP-Galp) and is an important virulence factor. UGM is a flavin-dependent enzyme that requires the reduced flavin for activity; flavin reduction is achieved by reaction with NADPH. The aim of this work was to discover inhibitors of UGM by targeting the NADPH binding site using an ADP-TAMRA probe in a high-throughput screening assay. The flavonoids …

Air-Oxidation Of Phenolic Resin Aerogels: Backbone Reorganization, Formation Of Ring-Fused Pyrylium Cations, And The Effect On Microporous Carbons With Enhanced Surface Areas, Hojat Majedi Far, Suraj Donthula, Tahereh Taghvaee, Adnan Malik Saeed, Zachary Garr, Chariklia Sotiriou-Leventis, Nicholas Leventis

Chemistry Faculty Research & Creative Works

This paper is a thorough investigation of the chemical transformations during pyrolytic conversion of phenolic resins to carbons, and reports that all carbons obtained from main-stream phenolic resins including phloroglucinol-formaldehyde (FPOL), phloroglucinol-terephthalaldehyde (TPOL), resorcinol-formaldehyde (RF), and phenol-formaldehyde (PF) contain fused pyrylium rings and charge-compensating phenoxides. Those four phenolic resins were prepared via a fast HCl-catalyzed process as low-density nanostructured solids classified as aerogels, which, owing to their open porosity, allowed air circulation through their bulk. In that regard, the first step of this study was the air-oxidation of those phenolic resin aerogels at 240 °C. In FPOL and TPOL aerogels, …

Investigation Of The Ozone Formation Reaction Pathway: Comparisons Of Full Configuration Interaction Quantum Monte Carlo And Fixed-Node Diffusion Monte Carlo With Contracted And Uncontracted Mrci, Andrew D. Powell, Nikesh S. Dattani, Rene F. K. Spada, Francisco B. C. Machado, Hans Lischka, Richard Dawes

Chemistry Faculty Research & Creative Works

The association/dissociation reaction path for ozone (O₂ + O ↔ O₃) is notoriously difficult to describe accurately using ab initio electronic structure theory, due to the importance of both strong and dynamic electron correlations. Experimentally, spectroscopic studies of the highest lying recorded vibrational states combined with the observed negative temperature dependence of the kinetics of oxygen isotope exchange reactions confirm that the reaction is barrierless, consistent with the latest potential energy surfaces. Previously reported potentials based on Davidson-corrected internally contracted multireference configuration interaction (MRCI) suffer from a spurious reef feature in the entrance channel even when extrapolated …

Characterization Of The Ornithine Hydroxylation Step In Albachelin Biosynthesis, Kendra Bufkin, Pablo Sobrado

Chemistry Faculty Research & Creative Works

N-Hydroxylating monooxygenases (NMOs) are involved in siderophore biosynthesis. Siderophores are high affinity iron chelators composed of catechol and hydroxamate functional groups that are synthesized and secreted by microorganisms and plants. Recently, a new siderophore named albachelin was isolated from a culture of Amycolatopsis alba growing under iron-limiting conditions. This work focuses on the expression, purification, and characterization of the NMO, abachelin monooxygenase (AMO) from A. alba. This enzyme was purified and characterized in its holo (FAD-bound) and apo (FAD-free) forms. The apo-AMO could be reconstituted by addition of free FAD. The two forms of AMO hydroxylate ornithine, while lysine increases …

Feni2se4–Reduced Graphene Oxide Nanocomposite: Enhancing Bifunctional Electrocatalytic Activity For Oxygen Evolution And Reduction Through Synergistic Effects, Siddesh Umapathi, Jahangir Masud, Abdurazag T. Swesi, Manashi Nath

Chemistry Faculty Research & Creative Works

Water splitting reaction using earth-abundant and environmentally benign catalysts is critical for renewable energy generation and storage. Herein a hybrid composite, FeNi₂Se₄ nanoparticles supported on nitrogen doped reduced graphene oxide (FeNi₂Se₄–NrGO) is reported as an efficient and dependable bifunctional electrocatalyst for oxygen evolution and oxygen reduction reactions (OER and ORR, respectively) under alkaline conditions. While FeNi₂Se₄ nanoparticles themselves show good catalytic activity for water oxidation, the constructed hybrid nanocomposite with NrGO as the supporting matrix show enhanced catalytic activity with a small overpotential of 170 mV @ 10 mA cm …

The Covalent Interaction Between Dihydrogen And Gold: A Rotational Spectroscopic Study Of H₂-Aucl, Daniel A. Obenchain, Derek S. Frank, Garry S. Grubbs, Herbert M. Pickett, Stewart E. Novick

Chemistry Faculty Research & Creative Works

The pure rotational transitions of H₂-AuCl have been measured using a pulsed-jet cavity Fourier transform microwave spectrometer equipped with a laser ablation source. The structure was found to be T-shaped, with the H-H bond interacting with the gold atom. Both ³⁵Cl and ³⁷Cl isotopologues have been measured for both ortho and para states of H2. Rotational constants, quartic centrifugal distortion constants, and nuclear quadrupole coupling constants for gold and chlorine have been determined. The use of the nuclear spin-nuclear spin interaction terms D_aa, D_bb, and D_cc for H₂ were required …

The Role Of Urinary Pteridines As Disease Biomarkers, Casey Burton, Yinfa Ma

Chemistry Faculty Research & Creative Works

Pteridines and their derivatives function as intermediates in the metabolism of several vitamins and cofactors, and their relevance to disease has inspired new efforts to study their roles as disease biomarkers. Recent analytical advances, such as the emergence of sensitive mass spectrometry techniques, new workflows for measuring pteridine derivatives in their native oxidation states and increased multiplexing capacities for the simultaneous determination of many pteridine derivatives, have enabled researchers to explore the roles of urinary pteridines as disease biomarkers at much lower levels with greater accuracy than with previous technologies or methods. As a result, urinary pteridines are being increasingly …

Inelastic Rate Coefficients For Collisions Of C₆Hˉ With H₂ And He, Kyle M. Walker, François Lique, Fabien Dumouchel, Richard Dawes

Chemistry Faculty Research & Creative Works

The recent detection of anions in the interstellar medium has shown that they exist in a variety of astrophysical environments -- circumstellar envelopes, cold dense molecular clouds and star-forming regions. Both radiative and collisional processes contribute to molecular excitation and de-excitation in these regions so that the ‘local thermodynamic equilibrium’ approximation, where collisions cause the gas to behave thermally, is not generally valid. Therefore, along with radiative coefficients, collisional excitation rate coefficients are needed to accurately model the anionic emission from these environments. We focus on the calculation of state-to-state rate coefficients of the C₆H^- molecule in …

Prevention And Reversal Of Selenite-Induced Cataracts By N-Acetylcysteine Amide In Wistar Rats, Yasaswi Maddirala, Shakila Tobwala, Humeyra Karacal, Nuran Ercal

Chemistry Faculty Research & Creative Works

Background: The present study sought to evaluate the efficacy of N-acetylcysteine amide (NACA) eye drops in reversing the cataract formation induced by sodium selenite in male Wistar rat pups.

Methods: Forty male Wistar rat pups were randomly divided into a control group, an N-acetylcysteine amide-only group, a sodium selenite-induced cataract group, and a NACA-treated sodium selenite-induced cataract group. Sodium selenite was injected intraperitoneally on postpartum day 10, whereas N-acetylcysteine amide was injected intraperitoneally on postpartum days 9, 11, and 13 in the respective groups. Cataracts were evaluated at the end of week 2 (postpartum day 14) when the rat pups …

Multifunctional Porous Aramids (Aerogels), Fabrication Thereof, And Catalytic Compositions Derived Therefrom, Nicholas Leventis, Chariklia Sotiriou-Leventis, Malik Adnan Saeed

Chemistry Faculty Research & Creative Works

The present disclosure provides a series of new and improved porous polyamide aerogels derived from multifunctional aromatics that combine the high mechanical strength of aramids with the pore structure of aerogels. The polyamide aerogels have a hyperbranched structure, relatively low density, high porosity and may be derived from functionalized monomers having more aromatic groups than functional groups. The present disclosure also provides a new method for producing the porous polyamide aerogels by polymerizing an aromatic multifunctional carboxylic acid or a ferrocene multifunctional carboxylic acid with a polyfunctional aromatic isocyanate at moderate reaction conditions followed by drying with liquid CO2. Also …

Does Plasticizer Penetrate Tightly Bound Polymer In Adsorbed Poly(Vinyl Acetate) On Silica?, Boonta Hetayothin, Roy A. Cabaniss, Frank D. Blum

Chemistry Faculty Research & Creative Works

When only tightly bound poly (vinyl acetate) (PVAc) was adsorbed on silica, the plasticizer, di(propylene glycol) dibenzoate (DPGDB), was not effective in lowering its glass transition. To determine why the plasticizer was not effective, we probed the behavior of the deuterated plasticizer di (propylene glycol) dibenzoate (DPGDB-d10)/PVAc/silica system using deuterium (2H) solid state NMR and temperature-modulated differential scanning calorimetry (TMDSC). PVAc with 37% (w/w) of plasticizer/polymer was adsorbed on silica in adsorbed amounts of 2.60 and 0.76 mg PVAc/m2 silica. The dynamics of the plasticizer in the adsorbed PVAc was found to be more motionally heterogeneous than that observed in …

Polycyclic Aromatic Hydrocarbons With Aliphatic Sidegroups: Intensity Scaling For The C-H Stretching Modes And Astrophysical Implications, Xuejuan Yang, Aigen Li, Rainer Glaser, Jianxin Zhong

Chemistry Faculty Research & Creative Works

The so-called unidentified infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm ubiquitously seen in a wide variety of astrophysical regions are generally attributed to polycyclic aromatic hydrocarbon (PAH) molecules. Astronomical PAHs may have an aliphatic component, as revealed by the detection in many UIE sources of the aliphatic C-H stretching feature at 3.4 mm. The ratio of the observed intensity of the 3.4 mm feature to that of the 3.3 μm aromatic C-H feature allows one to estimate the aliphatic fraction of the UIE carriers. This requires knowledge of the intrinsic oscillator strengths of the 3.3 …

Cost Effective Surface Functionalization Of Gold Nanoparticles With A Mixed Dna And Peg Monolayer For Nanotechnology Applications, Risheng Wang, Isabella Bowling, Wenyan Liu

Chemistry Faculty Research & Creative Works

A cost effective and generally applicable co-functionalization of gold nanoparticles with a mixed DNA and PEG polymers is reported. Compared to the pure DNA functionalization method, this protocol uses a much smaller amount of thiol-DNA to achieve a similar binding efficacy of gold nanoparticles with DNA origami nanostructures. The lower consumption of DNA provides a scaling-up potential for the application of DNA-nanoparticle conjugates in nanotechnology.

Inhibition Of The Flavin-Dependent Monooxygenase Siderophore A (Sida) Blocks Siderophore Biosynthesis And Aspergillus Fumigatus Growth, Julia S. Martín Del Campo, Nancy Vogelaar, Karishma Tolani, Karina Kizjakina, Kim Harich, Pablo Sobrado

Chemistry Faculty Research & Creative Works

Aspergillus fumigatus is an opportunistic fungal pathogen and the most common causative agent of fatal invasive mycoses. The flavin-dependent monooxygenase siderophore A (SidA) catalyzes the oxygen and NADPH dependent hydroxylation of l-ornithine (l-Orn) to N5-l-hydroxyornithine in the biosynthetic pathway of hydroxamate-containing siderophores in A. fumigatus. Deletion of the gene that codes for SidA has shown that it is essential in establishing infection in mice models. Here, a fluorescence polarization high-throughput assay was used to screen a 2320 compound library for inhibitors of SidA. Celastrol, a natural quinone methide, was identified as a noncompetitive inhibitor of SidA with a MIC value …

Elucidating The Effects Of Fluoro And Nitro Substituents On Halogen Bond Driven Assemblies Of Pyridyl-Capped Π-Conjugated Molecules, Suong T. Nguyen, Arnold L. Rheingold, Gregory S. Tschumper, Davita L. Watkins

Chemistry Faculty Research & Creative Works

Among recent advances toward efficient semiconducting materials, rational design guidelines have emerged focusing on the synergy between various intermolecular interactions to improve the solid-state order of π-conjugated molecules in organic electronic devices. Herein, we focus our attention on halogen bonding (XB) interactions and the crucial role of electron withdrawing substituents (e.g., nitro and fluoro) toward influencing solid-state properties via secondary interactions. Employing iodoethynyl benzene derivatives (F2BAI and (NO2)2BAI) and thiophene/furan-based building blocks equipped with pyridyl groups as self-assembling domains (PyrTF and PyrT2), co-crystals driven by XB, and π-stacking interactions were formed and studied. Spectroscopic and thermal analysis of 1:1 mixture …

The Structure Of The Antibiotic Deactivating, N-Hydroxylating Rifampicin Monooxygenase, Li Kai Liu, Heba Abdelwahab, Julia S. Martin Del Campo, Ritcha Mehra-Chaudhary, Pablo Sobrado, John J. Tanner

Chemistry Faculty Research & Creative Works

Rifampicin monooxygenase (RIFMO) catalyzes the N-hydroxylation of the natural product antibiotic rifampicin (RIF) to 2′-N-hydroxy-4-oxo-rifampicin, a metabolite with much lower antimicrobial activity. RIFMO shares moderate sequence similarity with well characterized flavoprotein monooxygenases, but the protein has not been isolated and characterized at the molecular level. Herein, we report crystal structures of RIFMO from Nocardia farcinica, the determination of the oligomeric state in solution with small angle x-ray scattering, and the spectrophotometric characterization of substrate binding. The structure identifies RIFMO as a class A flavoprotein monooxygenase and is similar in fold and quaternary structure to MtmOIV and OxyS, which are enzymes …

Mechanism Of Rifampicin Inactivation In Nocardia Farcinica, Heba Abdelwahab, Julia S.Martin Del Campo, Yumin Dai, Camelia Adly, Sohby El-Sohaimy, Pablo Sobrado

Chemistry Faculty Research & Creative Works

A novel mechanism of rifampicin (Rif) resistance has recently been reported in Nocardia farcinica. This new mechanism involves the activity of rifampicin monooxygenase (RifMO), a flavin-dependent monooxygenase that catalyzes the hydroxylation of Rif, which is the first step in the degradation pathway. Recombinant RifMO was overexpressed and purified for biochemical analysis. Kinetic characterization revealed that Rif binding is necessary for effective FAD reduction. RifMO exhibits only a 3-fold coenzyme preference for NADPH over NADH. RifMO catalyzes the incorporation of a single oxygen atom forming an unstable intermediate that eventually is converted to 20-N-hydroxy-4-oxo-Rif. Stable C4a-hydroperoxyflavin was not detected by rapid …

Competition Between Hydrophilic And Argyrophilic Interactions In Surface Enhanced Raman Spectroscopy, John T. Kelly, Annie K. Mcclellan, Lynn V. Joe, Ashley M. Wright, Lawson T. Lloyd, Gregory S. Tschumper, Nathan I. Hammer

Chemistry Faculty Research & Creative Works

The competition for binding and charge-transfer (CT) from the nitrogen containing heterocycle pyrimidine to either silver or to water in surface enhanced Raman spectroscopy (SERS) is discussed. The correlation between the shifting observed for vibrational normal modes and CT is analyzed both experimentally using Raman spectroscopy and theoretically using electronic structure theory. Discrete features in the Raman spectrum correspond to the binding of either water or silver to each of pyrimidine's nitrogen atoms with comparable frequency shifts. Natural bond orbital (NBO) calculations in each chemical environment reveal that the magnitude of charge transfer from pyrimidine to adjacent silver atoms is …

Room-Temperature Electrochemical Reduction Of Epitaxial Bi₂O₃ Films To Epitaxial Bi Films, Zhen He, Jakub Adam Koza, Ying-Chau Liu, Qingzhi Chen, Jay A. Switzer

Chemistry Faculty Research & Creative Works

This work reports a new facile approach to fabricate high-quality epitaxial Bi thin films by direct electrochemical reduction of epitaxial δ-Bi₂O₃ thin films on Au single crystals in aqueous solution at room-temperature. The as-produced Bi thin films (without any post-annealing process) exhibit large grain sizes, continuous microstructures, and enhanced magnetotransport properties.

Co7se8 Nanostructures As Catalysts For Oxygen Reduction Reaction With High Methanol Tolerance, Jahangir Masud, Manashi Nath

Chemistry Faculty Research & Creative Works

Co₇Se₈ nanostructures electrodeposited on glassy carbon (GC) electrodes show high efficiency for oxygen reduction reaction (ORR) with high methanol tolerance as compared to Pt electrocatalysts. In the presence of methanol, the onset potential for the ORR at Pt/GC is shifted from 0.931 V (vs reversible hydrogen electrode (RHE)) to 0.801 V (vs RHE), whereas it remains the same (0.811 V vs RHE) at Co₇Se₈/GC in the presence and absence of methanol in 0.5 M H₂SO₄ solution. The Co₇Se₈/GC electrodes also showed high cyclability in the presence …

The First Potential Energy Surfaces For The C₆Hˉ-H₂ And C₆Hˉ-He Collisional Systems And Their Corresponding Inelastic Cross Sections, Kyle M. Walker, Fabien Dumouchel, François Lique, Richard Dawes

Chemistry Faculty Research & Creative Works

Molecular anions have recently been detected in the interstellar and circumstellar media. Accurate modeling of their abundance requires calculations of collisional data with the most abundant species that are usually He atoms and H₂ molecules. In this paper, we focus on the collisional excitation of the first observed molecular anion, C₆H^-, by He and H₂. Theoretical calculations of collisional cross sections rely generally on ab initio interaction potential energy surfaces (PESs). Hence, we present here the first PESs for the C₆H^--H₂ and C₆H^--He van …

Single Particle Icp-Ms Method Development For The Determination Of Plant Uptake And Accumulation Of Ceo2 Nanoparticles, Yongbo Dan, Xingmao Ma, Weilan Zhang, Kun Liu, Chady Stephan, Honglan Shi

Chemistry Faculty Research & Creative Works

Cerium dioxide nanoparticles (CeO₂NPs) are among the most broadly used engineered nanoparticles that will be increasingly released into the environment. Thus, understanding their uptake, transportation, and transformation in plants, especially food crops, is critical because it represents a potential pathway for human consumption. One of the primary challenges for the endeavor is the inadequacy of current analytical methodologies to characterize and quantify the nanomaterial in complex biological samples at environmentally relevant concentrations. Herein, a method was developed using single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) technology to simultaneously detect the size and size distribution of particulate Ce, particle concentration, …

The C-H Stretching Features At 3.2-3.5 Μm Of Polycyclic Aromatic Hydrocarbons With Aliphatic Sidegroups, Xuejuan Yang, Aigen Li, Rainer Glaser, Jianxin Zhong

Chemistry Faculty Research & Creative Works

The so-called "unidentified" infrared emission (UIE) features at 3.3, 6.2, 7.7, 8.6, and 11.3 μm are ubiquitously seen in a wide variety of astrophysical regions. The UIE features are characteristic of the stretching and bending vibrations of aromatic hydrocarbon materials, e.g., polycyclic aromatic hydrocarbon (PAH) molecules. The 3.3 μm aromatic C-H stretching feature is often accompanied by a weaker feature at 3.4 μm. The latter is generally thought to result from the C-H stretch of aliphatic groups attached to the aromatic systems. The ratio of the observed intensity of the 3.3 μm aromatic C-H feature to that of the 3.4 …

Coupling Between Magnetic Exchange And Charge Activation In Cu-Doped Lafeo3, Emir Dogdibegovic, Qingsheng Cai, William Joseph James, William B. Yelon, Harlan U. Anderson, Jin Bo Yang, Xiao Dong Zhou

Chemistry Faculty Research & Creative Works

Material research on perovskite-type oxides (ABO₃) has been driven by the recognition of their unique properties primarily attributed to the presence of oxygen octahedron (BO₆). Since 2003, the discovery of strong coupling in TbMnO₃ and BiFeO₃ has stimulated new interests in understanding the relationship between magnetic and electric properties in perovskites. In this article, we report our recent work on the magnetic superexchange interaction and charge formation in copper-doped LaFeO₃ using high-temperature neutron diffraction and thermoelectric measurements. In situ neutron diffraction measurements show a loss of antiferromagnetic ordering above 450°C. With an increase …

Water Quality In Selected Small Drinking Water Systems Of Missouri Rural Communities, Bin Hua, Ruipu Mu, Honglan Shi, Enos Inniss, John Yang

Chemistry Faculty Research & Creative Works

Small drinking water treatment systems (serving < 10,000 population) in rural communities frequently encounter multiple challenges in water quality and federal regulatory compliance, especially the disinfection byproduct (DBP) regulations, due to source water variations, limited resources, and aging infrastructures. Unlike most studies on the DBP control using synthetic water in laboratory settings, this research aimed to identify the major water quality issues confronting small systems in the state of Missouri (MO), the United States of America (USA). Three small systems were selected based on source water and geographic locations. Water samples were collected quarterly from each major treatment process during the period of May 2012 to March 2013 and analyzed to identify the treatment effectiveness and potential water quality issues in each small system. Results of water quality characterization showed that the major water quality issue in the selected small systems was the low efficiency of dissolved organic carbon (DOC) removal, especially the DOC species that are considered as the DBP precursors. Most collected water samples had a higher trihalomethane formation potential (THMFP) than the United States Environmental Protection Agency (USEPA) maximum contaminant limit (MCL) (80 µg/L). Based on the analysis of the treatment efficiency in each system, several strategies for water quality improvement were recommended, and a few of which have been implemented in the small systems, leading to improved drinking water quality and compliance with the USEPA DBP regulations. This study would provide a valuable aid to small system operators and local water authority in context of water quality improvement and the regulatory compliance.

A New Set Of Potential Energy Surfaces For Hco: Influence Of Renner-Teller Coupling On The Bound And Resonance Vibrational States, Steve Alexandre Ndengué, Richard Dawes, Hua Guo

Chemistry Faculty Research & Creative Works

It is commonly understood that the Renner-Teller effect can strongly influence the spectroscopy of molecules through coupling of electronic states. Here we investigate the vibrational bound states and low-lying resonances of the formyl radical treating the Renner-Teller coupled X2A' and Ã2A" states using the MultiConfiguration Time Dependent Hartree (MCTDH) method. The calculations were performed using the improved relaxation method for the bound states and a recently published extension to compute resonances. A new set of accurate global potential energy surfaces were computed at the explicitly correlated multireference configuration interaction (MRCI-F12) level and yielded remarkably close agreement with experiment in this …

Employing Synergetic Effect Of Doping And Thin Film Coating To Boost The Performance Of Lithium-Ion Battery Cathode Particles, Rajankumar L. Patel, Yingbing Jiang, Amitava Choudhury, Xinhua Liang

Chemistry Faculty Research & Creative Works

Atomic layer deposition (ALD) has evolved as an important technique to coat conformal protective thin films on cathode and anode particles of lithium ion batteries to enhance their electrochemical performance. Coating a conformal, conductive and optimal ultrathin film on cathode particles has significantly increased the capacity retention and cycle life as demonstrated in our previous work. In this work, we have unearthed the synergetic effect of electrochemically active iron oxide films coating and partial doping of iron on LiMn_1.5 Ni_0.5O₄ (LMNO) particles. The ionic Fe penetrates into the lattice structure of LMNO during the ALD process. …

Big Changes For Small Noncovalent Dimers: Revisiting The Potential Energy Surfaces Of (P2)2 And (Pccp)2 With Ccsd(T) Optimizations And Vibrational Frequencies, Eric Van Dornshuld, Gregory S. Tschumper

Chemistry Faculty Research & Creative Works

This article details the re-examination of low-lying stationary points on the potential energy surfaces (PESs) of two challenging noncovalent homogeneous dimers, (P₂)₂ and (PCCP)₂. The work was motivated by the rather large differences between MP2 and CCSD(T) energetics that were recently reported for these systems (J. Comput. Chem. 2014, 35, 479-487). The current investigation reveals significant qualitative and quantitative changes when the CCSD(T) method is used to characterize the stationary points instead of MP2. For example, CCSD(T) optimizations and harmonic vibrational frequency computations with the aug-cc-pVTZ basis set indicate that the parallel-slipped (PS) structure is …