Evaluating interaction energy versus electron density relationships to estimate inter and intramolecular H-bonding.

We investigate the computational effects on the relationships between interaction energy (ΔE) and electron density (ρ), at the critical point obtained from 19 intermolecular H-bonded dimers, to estimate inter and intramolecular interactions of larger H-bonded systems. Our analysis examines basis set superposition error (BSSE) effects, dispersion energy corrections, and the exchange-correlation energy model on the ΔE vs. ρ linear regressions.

Au@AuPd Core-Alloyed Shell Nanoparticles for Enhanced Electrocatalytic Activity and Selectivity under Visible Light Excitation.

Plasmonic catalysis has been employed to enhance molecular transformations under visible light excitation, leveraging the localized surface plasmon resonance (LSPR) in plasmonic nanoparticles. While plasmonic catalysis has been employed for accelerating reaction rates, achieving control over the reaction selectivity has remained a challenge. In addition, the incorporation of catalytic components into traditional plasmonic-catalytic antenna-reactor nanoparticles often leads to a decrease in optical absorption.

A theoretical study of the photochemistry of 1,3-cyclopentadiene and its cyano derivatives bound to a water dimer: Assessing reactivity of ionized clusters and possible photoproducts.

We theoretically investigate the photoionization scenarios of molecular complexes involving cyclopentadiene and cyanocyclopentadiene bound to water dimers. Using electronic structure calculations within density-functional theory (DFT) and time dependent DFT (TD-DFT), we explore the potential photochemical pathways following ionization, and determine the charge transfer excitations related to the possible subsequent reactions. Our findings suggest that the investigated photochemical pathways of the hydrated complexes take place in two well-defined ultraviolet regions: (i) 8.

The Interplay between the Temperature and Pressure on the Reaction Pathways of the Prenol Oxidation by Hydroxyl Radicals.

Despite prenol emerging as a next-generation biofuel, some questions about its mechanism still need to be adequately proposed to rationalize its consumption and evaluate its efficiency in spark-ignition (SI) engines. Here, we present new insights into the reaction mechanism of prenol (3-methyl-2-buten-1-ol) with OH radicals as a function of temperature and pressure. We have determined that the different temperature and pressure conditions control the preferred products.

Influence of Solvents and Halogenation on ESIPT of Benzimidazole Derivatives for Designing Turn-on Fluorescence Probes.

This work reports a theoretical investigation of the solvent polarity as well as the halogenation of benzimidazole derivatives during excited state intramolecular proton transfer (ESIPT). It details how the environment and halogen substitution may contribute to the efficiency of ESIPT upon keto-enol tautomerism and exploits this effect to design fluorescence sensing. For this purpose, we first examine the conformational equilibrium of benzimidazole derivatives containing different halogen atoms, which results in intramolecular proton transfer, using density-functional theory (DFT) combined with the polarizable continuum model (PCM).

Predicting pressure-dependent rate constants for the furan + OH reactions and their impact under tropospheric conditions.

In this work, we have evaluated the influence of temperature and pressure on the mechanism of furan oxidation by the OH radical. The stationary points on the potential energy surface were described at the M06-2X/aug-cc-pVTZ level of theory. In the kinetic treatment at the high-pressure limit (HPL), we have combined the multistructural canonical variational theory with multidimensional small-curvature tunneling corrections and long-range transition state theory.

Understanding the reactivity and selectivity of Diels-Alder reactions involving furans.

The reactivity and / selectivity of the Diels-Alder cycloaddition reactions involving furan and substituted furans as dienes have been computationally explored. In comparison to cyclopentadiene, it is found that furan is comparatively less reactive and also less -selective in the reaction with maleic anhydride as the dienophile. Despite that, both the reactivity and the selectivity can be successfully modified by the presence of substituents at either 2- or 3-positions of the heterocycle.

Multistructural partition function truncation and its effect on the thermal rate constants.

Thermal rate constants for the hydrogen abstraction reaction of methyl pentanoate were calculated using the multistructural canonical variational theory with small-curvature tunneling (MS-CVT/SCT). The conformational search for the stationary points generated by these reactions was performed with an algorithm that combines systematic and stochastic searches at dual-level. At the high-level (MPWB1K/6-31+G(d,p)), 244 geometries for methyl pentanoate and transition states were found.

Photoabsorption of Microhydrated Naphthalene and Its Cyano-Substituted Derivatives: Probing Prereactive Models for Photodissociation in Molecular Clouds.

We investigate the photoionization pathways of naphthalene, 1-cyanonaphthalene, and 2-cyanonaphthalene upon complexation with the water dimer, aiming to understand the photodissociation process under conditions of the interstellar medium (ISM). We analyze the intermolecular bonding pattern, equilibrium rotational properties, energy complexation, far-IR spectra, and ionic trends of the possible photoproducts using dispersion-corrected density functional theory (DFT-D) and time-dependent DFT (TD-DFT). For the different configurations, we evaluate the possible charge-transfer (CT) excitations near the photoionization limit.

Prenol as a Next-Generation Biofuel or Additive: A Comprehension of the Hydrogen Abstraction Reactions by a H Atom.

Thermal rate coefficients for the hydrogen abstraction reactions of prenol (3-methyl-2-butenol) by a hydrogen atom were calculated with the multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT). The conformational search was performed with a dual-level approach, and the multistructural torsional anharmonicity effects were corrected through the rovibrational partition function calculated with the multistructural method based on a coupled torsional potential (MS-T(C)). This methodology allows us to estimate the thermal rate constants in the temperature range of 200-2500 K and fit them into two analytical expressions.

Differences in the torsional anharmonicity between reactant and transition state: the case of 3-butenal + H abstraction reactions.

Thermal rate coefficients for the hydrogen-abstraction reactions of 3-butenal by a hydrogen atom were obtained applying multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT). Torsional anharmonicity due to the hindered rotors was taken into account by calculating the rovibrational partition function using the extended two-dimensional torsional (E2DT) method. For comparison, rovibrational partition functions were also estimated using the multistructural method with torsional anharmonicity based on a coupled torsional potential (MS-T(C)).

Rate coefficients and product branching ratios for (E)-2-butenal + H reactions.

Thermal rate constants for the hydrogen abstraction reactions of (E)-2-butenal by hydrogen atoms were calculated, for the first time, using the multipath canonical variational theory with small-curvature tunneling (MP-CVT/SCT). After a torsional potential energy surface exploration, ten conformations of the transition states (including the mirror images) were found and separated into four conformational reaction channels (CRCs). Individual energy paths of each CRC were built, recrossing and quantum tunneling effects estimated, and the thermal rate constants obtained.

Design-controlled synthesis of IrO sub-monolayers on Au nanoflowers: marrying plasmonic and electrocatalytic properties.

We develop herein plasmonic-catalytic Au-IrO nanostructures with a morphology optimized for efficient light harvesting and catalytic surface area; the nanoparticles have a nanoflower morphology, with closely spaced Au branches all partially covered by an ultrathin (1 nm) IrO shell. This nanoparticle architecture optimizes optical features due to the interactions of closely spaced plasmonic branches forming electromagnetic hot spots, and the ultra-thin IrO layer maximizes efficient use of this expensive catalyst. This concept was evaluated towards the enhancement of the electrocatalytic performances towards the oxygen evolution reaction (OER) as a model transformation.

Variational transition state theory rate constants and H/D kinetic isotope effects for CH + CH OCOH reactions.

The rate constants and H/D kinetic isotope effect for hydrogen abstraction reactions involving isotopomers of methyl formate by methyl radical are computed employing methods of the variational transition state theory (VTST) with multidimensional tunneling corrections. The energy paths were built with a dual-level method using the moller plesset second-order perturbation theory (MP2) method as the low-level and complete basis set (CBS) extrapolation as the high-level energy method. Benchmark calculations with the CBS approach give an enthalpy of reaction at 0 K for R1 (-4.

Controlling Reaction Selectivity over Hybrid Plasmonic Nanocatalysts.

The localized surface plasmon resonance (LSPR) excitation in plasmonic nanoparticles has been used to accelerate several catalytic transformations under visible-light irradiation. In order to fully harness the potential of plasmonic catalysis, multimetallic nanoparticles containing a plasmonic and a catalytic component, where LSPR-excited energetic charge carriers and the intrinsic catalytic active sites work synergistically, have raised increased attention. Despite several exciting studies observing rate enhancements, controlling reaction selectivity remains very challenging.

Anharmonicity of Coupled Torsions: The Extended Two-Dimensional Torsion Method and Its Use To Assess More Approximate Methods.

In this work we present the extended two-dimensional torsion (E2DT) method and use it to analyze the performance of several methods that incorporate torsional anharmonicity more approximately for calculating rotational-vibrational partition functions. Twenty molecules having two hindered rotors were studied for temperatures between 100 and 2500 K. These molecules present several kinds of situations; they include molecules with nearly separable rotors, molecules in which the reduced moments of inertia change substantially with the internal rotation, and molecules presenting compound rotation.

On the Effect of Native SiO on Si over the SPR-mediated Photocatalytic Activities of Au and Ag Nanoparticles.

In hybrid materials containing plasmonic nanoparticles such as Au and Ag, charge-transfer processes from and to Au or Ag can affect both activities and selectivity in plasmonic catalysis. Inspired by the widespread utilization of commercial Si wafers in surface-enhanced Raman spectroscopy (SERS) studies, we investigated herein the effect of the native SiO layer on Si wafers over the surface plasmon resonance (SPR)-mediated activities of the Au and Ag nanoparticles (NPs). We prepared SERS-active plasmonic comprised of Au and Ag NPs deposited onto a Si wafer.

Plasmonic Nanorattles as Next-Generation Catalysts for Surface Plasmon Resonance-Mediated Oxidations Promoted by Activated Oxygen.

Nanorattles, comprised of a nanosphere inside a nanoshell, were employed as the next generation of plasmonic catalysts for oxidations promoted by activated O2 . After investigating how the presence of a nanosphere inside a nanoshell affected the electric-field enhancements in the nanorattle relative to a nanoshell and a nanosphere, the SPR-mediated oxidation of p-aminothiophenol (PATP) functionalized at their surface was investigated to benchmark how these different electric-field intensities affected the performances of Au@AgAu nanorattles, AgAu nanoshells and Au nanoparticles having similar sizes. The high performance of the nanorattles enabled the visible-light driven synthesis of azobenzene from aniline under ambient conditions.

Hindered rotor tunneling splittings: an application of the two-dimensional non-separable method to benzyl alcohol and two of its fluorine derivatives.

In this work we present a novel application of the two-dimensional non-separable (2D-NS) method to the calculation of torsional tunneling splittings in systems with two hindered internal rotors. This method could be considered an extension of one-dimensional methods for the case of compounds with two tops. The 2D-NS method includes coupling between torsions in the kinetic and potential energy.

Theoretical Design and Experimental Realization of Quasi Single Electron Enhancement in Plasmonic Catalysis.

By a combination of theoretical and experimental design, we probed the effect of a quasi-single electron on the surface plasmon resonance (SPR)-mediated catalytic activities of Ag nanoparticles. Specifically, we started by theoretically investigating how the E-field distribution around the surface of a Ag nanosphere was influenced by static electric field induced by one, two, or three extra fixed electrons embedded in graphene oxide (GO) next to the Ag nanosphere. We found that the presence of the extra electron(s) changed the E-field distributions and led to higher electric field intensities.

Kinetic Isotope Effects in Multipath VTST: Application to a Hydrogen Abstraction Reaction.

In this work we apply multipath canonical variational transition state theory with small-tunneling corrections (MP-CVT/SCT) to the hydrogen abstraction reaction from ethanol by atomic hydrogen in aqueous solution at room temperature. This reaction presents two transition states which can interconvert by internal rotations about single bonds and another two transition states that are non-interconvertible enantiomers to the former structures. The study also includes another three reactions with isotopically substituted species for which there are experimental values of thermal rate constants and kinetic isotope effects (KIEs).

The Fault in Their Shapes: Investigating the Surface-Plasmon-Resonance-Mediated Catalytic Activities of Silver Quasi-Spheres, Cubes, Triangular Prisms, and Wires.

The surface-plasmon-resonance (SPR)-mediated catalytic activities of Ag and Au nanoparticles have emerged a relatively new frontier in catalysis in which visible light can be employed as an eco-friendly energy input to drive chemical reactions. Although this phenomenon has been reported for a variety of transformations, the effect of the nanoparticle shape and crystalline structure on the activities remains unclear. In this paper, we investigated the SPR-mediated catalytic activity of Ag quasi-spheres, cubes, triangular prisms, and wires toward the oxidation of p-aminothiophenol to p,p'-dimercaptoazobenzene by activated O2.

Exploring the electronic states of iodocarbyne: a theoretical contribution.

A manifold of electronic states correlating with the two lowest-lying dissociation channels of the iodocarbyne (CI) species is theoretically characterized for the first time in the literature. A contrast between the Λ + S and the relativistic (Ω) descriptions clearly shows the effect of perturbations on electronic states above 20 000 cm(-1) and the potential difficulties to detect them experimentally. For the bound states, spectroscopic parameters were evaluated, as well as the dipole moment functions.

Calcium-containing diatomic dications in the gas phase.

Sputtering (ion surface bombardment) of various calcium-containing powder samples with an energetic (17 keV), high-current (16)O(-) beam has produced the diatomic dications of CaSi(2+), CaP(2+), CaF(2+), CaH(2+), CaCl(2+), CaBr(2+) and CaI(2+). These molecular gas-phase species have been identified in positive ion mass spectra at half-integer m/z values; their ion flight times through a magnetic-sector mass spectrometer were roughly 10(-5) s. Most of them appear to be novel molecular ions; the stability of the latter four (CaH(2+), CaCl(2+), CaBr(2+) and CaI(2+)) had been demonstrated in previous theoretical studies, whereas only CaF(2+) and CaBr(2+) had been observed before.