Lester Andrews

Bio: Lester Andrews is an academic researcher from University of Virginia. The author has contributed to research in topics: Infrared spectroscopy & Molecule. The author has an hindex of 68, co-authored 888 publications receiving 24613 citations. Previous affiliations of Lester Andrews include Ames Research Center & Environmental Molecular Sciences Laboratory.

Reactions of Pulsed-Laser-Evaporated Thallium Atoms with O2. Matrix Infrared Spectra of New TlO2 Species. Trends in Group 13 Dioxides and Dioxide Anions

Abstract: Laser-ablated Tl atoms react with O2 to give a new linear insertion product OTlO and the dimer TlOTlO in addition to the cyclic Tl(O2), TlO2Tl, and Tl4O2 products observed in earlier thermal effusi...

Spectroscopic observation of photo-induced metastable linkage isomers of coinage metal (Cu, Ag, Au) sulfur dioxide complexes

Abstract: Coinage metal atom (Cu, Ag, Au) reactions with SO2 were investigated by matrix isolation infrared absorption spectroscopy and density functional theory electronic structure calculations. Both mononuclear complexes M(η1-SO2) (M = Ag, Au) and M(η2-O2S) (M = Ag, Cu) were observed during condensation in solid argon or neon. Interestingly, the silver containing mononuclear complexes are interconvertible; that is, visible light induces the isomerization of Ag(η1-SO2) to Ag(η2-O2S) and vice versa on annealing. However, there is no evidence of similar interconvertibility for the Cu(η2-O2S) and Au(η1-SO2) molecules. These different behaviors are discussed within the bonding considerations for all of the obtained products.

Reactions of Laser-Ablated Ruthenium Atoms with CO and H2 Mixtures: Infrared Spectra and Density Functional Theory Calculations of H2Ru(CO)x (x = 2−4) and (H2)RuCO

Abstract: Reactions of laser-ablated ruthenium atoms with carbon monoxide and hydrogen in solid argon produce the unsaturated ruthenium carbonyl dihydride H2Ru(CO)2 and the hydrogen complexes (H2)xRuCO (x = 1, 2). The observed absorption bands of the reaction products are identified by isotopic substitution and reproduced well by DFT calculations of vibrational fundamentals. The growth of bands due to H2Ru(CO)2 and (H2)RuCO during annealing in solid argon indicates that ruthenium monocarbonyl is coordinated with H2 to form the dihydrogen complex (H2)RuCO, while H2Ru(CO)2 is formed from the (H2)RuCO complex inserting into (H2) upon coordinating with another CO. Weak bands due to H2Ru(CO)3 and H2Ru(CO)4 are also observed.

Matrix infrared spectroscopic and density functional theoretical investigations on thorium and uranium atom reactions with dimethyl ether

Abstract: Reactions of laser-ablated thorium and uranium atoms with dimethyl ether were investigated using matrix isolation infrared spectroscopy. Four types of reaction products for both uranium and thorium were identified using deuterium substituted samples as well as density functional frequency and energy calculations. Ground state uranium and thorium atoms react with dimethyl ether spontaneously to give the M(CH3OCH3) complexes (M = Th, U) on annealing, which are predicted to have C2v symmetry with triplet (Th) and quintet (U) ground states. Subsequent visible irradiation produces the divalent CH3OThCH3 and CH3OUCH3 insertion products with singlet and quintet states lowest in energy. Further UV irradiation induces isomerization of the CH3OMCH3 molecules to the (CH3)2MO isomers with MO double bonds and pyramidal structures. In the presence of another dimethyl ether reagent, evidence for (CH3O)2M(CH3)2 molecules is also produced upon UV irradiation.

A Chemist's Guide to Density Functional Theory

Abstract: "Chemists familiar with conventional quantum mechanics will applaud and benefit greatly from this particularly instructive, thorough and clearly written exposition of density functional theory: its basis, concepts, terms, implementation, and performance in diverse applications. Users of DFT for structure, energy, and molecular property computations, as well as reaction mechanism studies, are guided to the optimum choices of the most effective methods. Well done!" Paul von RaguE Schleyer "A conspicuous hole in the computational chemist's library is nicely filled by this book, which provides a wide-ranging and pragmatic view of the subject.[...It] should justifiably become the favorite text on the subject for practioneers who aim to use DFT to solve chemical problems." J. F. Stanton, J. Am. Chem. Soc. "The authors' aim is to guide the chemist through basic theoretical and related technical aspects of DFT at an easy-to-understand theoretical level. They succeed admirably." P. C. H. Mitchell, Appl. Organomet. Chem. "The authors have done an excellent service to the chemical community. [...] A Chemist's Guide to Density Functional Theory is exactly what the title suggests. It should be an invaluable source of insight and knowledge for many chemists using DFT approaches to solve chemical problems." M. Kaupp, Angew. Chem.

The density functional formalism, its applications and prospects

Abstract: A scheme that reduces the calculations of ground-state properties of systems of interacting particles exactly to the solution of single-particle Hartree-type equations has obvious advantages. It is not surprising, then, that the density functional formalism, which provides a way of doing this, has received much attention in the past two decades. The quality of the energy surfaces calculated using a simple local-density approximation for exchange and correlation exceeds by far the original expectations. In this work, the authors survey the formalism and some of its applications (in particular to atoms and small molecules) and discuss the reasons for the successes and failures of the local-density approximation and some of its modifications.

The Halogen Bond

Abstract: The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

Generation and Detection of Reactive Oxygen Species in Photocatalysis

Abstract: The detection methods and generation mechanisms of the intrinsic reactive oxygen species (ROS), i.e., superoxide anion radical (•O2–), hydrogen peroxide (H2O2), singlet oxygen (1O2), and hydroxyl radical (•OH) in photocatalysis, were surveyed comprehensively. Consequently, the major photocatalyst used in heterogeneous photocatalytic systems was found to be TiO2. However, besides TiO2 some representative photocatalysts were also involved in the discussion. Among the various issues we focused on the detection methods and generation reactions of ROS in the aqueous suspensions of photocatalysts. On the careful account of the experimental results presented so far, we proposed the following apprehension: adsorbed •OH could be regarded as trapped holes, which are involved in a rapid adsorption–desorption equilibrium at the TiO2–solution interface. Because the equilibrium shifts to the adsorption side, trapped holes must be actually the dominant oxidation species whereas •OH in solution would exert the reactivity...

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Abstract: : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg