Non-heme iron and manganese species with terminal oxo ligands are proposed to be key intermediates in a variety of biological synthetic systems; however, the stabilization these types complexes has proven difficult because tendency form oxo-bridged complexes. Described herein design, isolation, properties for series mononuclear FeIII MnIII or hydroxo ligands. Isolation was facilitated by tripodal ligand tris[(N'-tert-butylureaylato)-N-ethyl]aminato ([H3 1]3-), which creates protective...

Recent advances in the calculation and interpretation of activation energy for a dynamical process are described. Specifically, new approaches that apply fluctuation theory statistical mechanics to dynamics enable direct determination an arbitrary time scale from simulations at single temperature. This opens up significant possibilities understanding activated processes cases where traditional Arrhenius analysis is not possible. The methods also rigorous decomposition into contributions...

Liquids confined on nanometer lengthscales are ubiquitous in chemistry, occurring systems ranging from mesoporous catalysts to the crowded interior of a cell. Understanding how properties liquid these environments differs that corresponding bulk is key interpreting measurements, developing methods for theoretical predictions, and controlling chemical pathways. This area has received significant attention recent years, resulting notable progress. In this perspective, we discuss advances...

We investigate the nature of hydrogen bonding in gas-phase halide−water clusters (X-···H2O), with special emphasis on how affects frequency hydrogen-bonded OH stretch. present two models for describing electronic structure bond. The first model (non-charge-transfer, or non-CT) includes only electrostatic interactions between halide ion and water molecule. second is a two-valence-bond (VB) state which VB has charge character X-···H2O charge-transfer XH···OH-. find that non-CT inadequate...

The reorientation dynamics of water confined within nanoscale, hydrophilic silica pores are investigated using molecular simulations. effect surface hydrogen-bonding and electrostatic interactions examined by comparing with both a pore no charges (representing hydrophobic confinement) bulk water. OH in is found to slow significantly confinement compared water, well-described power-law decay extending beyond one nanosecond. In contrast, the more modestly affected. A two-state model, commonly...

Toll-like receptor (TLR) 7 and 8 agonists are potential vaccine adjuvants, since they directly activate APCs enhance Th1-driven immune responses. Previous SAR investigations in several scaffolds of small molecule TLR7/8 activators pointed to the strict dependence selectivity for TLR7 vis-à-vis TLR8 on electronic configurations heterocyclic systems, which we sought examine quantitatively with goal developing "heuristics" define structural requisites governing activity at and/or TLR8. We...

The self-diffusion of water molecules plays a key part in broad range essential processes biochemistry, medical imaging, material science, and engineering. However, its molecular mechanism the role played by hydrogen-bond network rearrangements are not known. Here we combine dynamics simulations analytic modeling to determine diffusion. We establish quantitative connection between diffusion coefficient jump exchanges, identify features that underlying energetic barrier. thus provide unified...

We present a method for obtaining the thermal rate constant directly (i.e., without first solving state-to-state reactive scattering problem) from time integral of flux-flux autocorrelation function, Cff(t). The quantum mechanical trace involved in calculating Cff(t) is efficiently evaluated by taking advantage low rank Boltzmannized flux operator. propagation carried out with Hamiltonian which includes imaginary absorbing potentials reactant and product exit channels. These eliminate...

Nanoconfined liquids are of interest because both their fundamental properties and potential utility in an array applications. The structure dynamics the liquid can be dramatically impacted by geometrical constraints interactions with interface. Understanding molecular-level origins these changes how they determined characteristics confining framework is subject ongoing experimental theoretical studies. progress remaining challenges efforts reviewed context solvation proton transfer...

Allyl sulfonylacetic esters undergo highly stereospecific, palladium-catalyzed decarboxylative allylation. The reaction allows the stereospecific formation of tertiary homoallylic sulfones in high yield. In contrast to related reactions that proceed at −100 °C and require basic preformed organometallics, coupling described herein occurs under mild nonbasic conditions requires no stoichiometric additives. Allylation intermediate α-sulfonyl anion is more rapid than racemization, leading a...

Electronic structure calculations have been used to investigate possible gas-phase decomposition pathways of α-hydroxyalkyl hydroperoxides (HHPs), an important source tropospheric hydrogen peroxide and carbonyl compounds. The uncatalyzed as well water- acid-catalyzed multiple HHPs examined at the M06-2X/aug-cc-pVTZ level theory. indicate that, compared or water-catalyzed reaction, free-energy barrier leading aldehyde ketone is dramatically lowered. also find a direct correlation between...

Electronic structure calculations indicate that the organic acids catalyze tautomerization of Criegee intermediates <italic>via</italic> a 1,4 β-hydrogen atom transfer to yield vinyl hydroperoxide such an extent it becomes barrierless process.

Many questions remain about the reactions of hydrated electron despite decades study. Of particular note is that they do not appear to follow Marcus theory transfer reactions, a feature yet be explained. To investigate these issues, we used ab initio molecular dynamics (AIMD) simulations one better studied reduction CO2. The rate constant for electron–CO2 reaction complex react form CO2– first time estimated from AIMD simulations. Results at 298 and 373 K show insensitive temperature,...

Fluid-silica interfaces are ubiquitous in chemistry, occurring both natural geochemical environments and practical applications ranging from separations to catalysis. Simulations of these have been, continue be, a significant avenue for understanding their behavior. A constraining factor, however, is the availability accurate force fields. Most simulations use traditional "mixing rules" determine nonbonded dispersion interactions, an approach that has not been critically examined. Here, we...

An efficient method was recently introduced by Thompson and Miller [J. Chem. Phys. 106, 142 (1997)] for calculating thermal rate constants using the flux–flux autocorrelation function with absorbing boundary conditions. The uses an iterative to exploit low rank feature of Boltzmannized flux operator subsequently only propagates eigenvectors that have significant contributions constant. In present article, this is used calculate Cl+H2→HCl+H reaction in temperature range 200–1500 °K. Total...

Molecular dynamics simulations of the conformational equilibrium ethylene glycol in roughly cylindrical nanoscale amorphous silica pores are presented and analyzed context a two-state model confined liquids. This assumes that an observable property liquid can be decomposed into weighted average arising from two subensembles with distinct physical attributes: molecules at surface interior pore. It is further assumed exhibit behavior indistinguishable bulk liquid. However, present simulation...

The infrared spectrum of acetonitrile confined in hydrophilic silica pores roughly cylindrical and 2.4 nm diameter has been simulated using molecular dynamics. Hydrogen bonding interactions between silanol groups on the pore wall involve charge transfer effects that have incorporated through corrections based electronic structure calculations a dimer. differs most prominently from bulk liquid by appearance blue-shifted shoulder, agreement with previous experimental measurements. dominant...

A doubly hydrogen-bonded interaction between the Criegee intermediate and a deuterated carboxylic acid facilitates efficient H/D transfer to yield partially vinyl hydroperoxide.

Many of water’s remarkable properties arise from its tendency to form an intricate and robust hydrogen bond network. Understanding the dynamics that govern this network is fundamental elucidating behavior pure water in biological physical systems. In ultrafast nonlinear infrared experiments, accessible time scales are limited by rapid vibrational relaxation (1.8 ps for dilute HOD H2O), precluding interrogation slow evolution non-bulk Here, bonding bulk D2O were studied perspective much...

The structure and dynamics of phospholipid reverse micelles are studied by molecular dynamics. We report all-atom unconstrained simulations 1,2-dioleoyl-sn-phosphatidylcholine (DOPC) in benzene increasing sizes, with water-to-surfactant number ratios ranging from W0 = 1 to 16. aggregation number, i.e., the DOPC molecules per micelle, is determined fit experimental light-scattering measurements micelle diameter. simulated found be approximately spherical. Larger (W0 > 4) exhibit a layered...

Nanoporous silica materials are important in catalysis, energy, and applications which water is an essential component. System performance intimately connected to the dynamics occurring confined environment. However, associated structures of nanoporous have proven challenging measure predict. Here, examined via ultrafast infrared spectroscopy selenocyanate (SeCN–) dissolved hydrated ∼2.4 nm mesopores MCM41. Polarization selective pump–probe two-dimensional measurements on CN stretching mode...

Electrolyte conductivity contributes to the efficiency of devices for electrochemical conversion carbon dioxide (CO2) into useful chemicals, but effect dissolution CO2 gas on has received little attention. Here, we report a joint experimental–theoretical study properties acetonitrile-based CO2-expanded electrolytes (CXEs) that contain high concentrations (up 12 M), achieved by pressurization. Cyclic voltammetry data and paired simulations show dissolved do not impede kinetics outer-sphere...

We present a new approach for the direct (and correct) calculation of thermal rate constants k(T) (‘‘direct’’ meaning that one avoids having to solve state-to-state reactive scattering problem, and ‘‘correct’’ method contains no inherent approximations). The constant is obtained from long time limit flux-position correlation function, Cf,s(t), whose made efficient by taking advantage low rank flux operator. Specifically, trace required obtain Cf,s(t) evaluated Lanczos iteration procedure...