High-Order Harmonic Generation from the Cu(111) surface

We investigate theoretically the origin behind the formation of the plateau and cutoff structures in the high-harmonic spectra produced after the interaction of a near-infrared laser pulse with a metal surface. We use a wave packet propagation scheme and a one dimensional description of the Cu(111) surfac

Dynamics of excited clusters of β-alanine in the gas phase

We present a theoretical study of excited clusters of β-alanine molecules in the gas phase: (β-ala)n, n=2-5. Classical molecular dynamics simulations performed for different internal excitation energies showed a thermal decomposition dependence with the cluster size. We also present an assessment study performed with different families of density functionals using the dimer, (β-ala)2 as a benchmark system. M06-2X provides the best agreement for the relative energies of 20 isomers in comparison with the reference values computed with the MP2 method. The stability and reactivity of several cluster sizes have been investigated with this functional in combination with the 6-311++G(d,p) basis se

New features in the ionic states of N2O4: Experimental and theoretical study

We present a combined experimental and theoretical study focused on the ionic states of the N2O4 molecule. Experimental results regarding photoionization induced by the synchrotron radiation SOLEIL in the 13.5-15.5 eV energy range were obtained using the electron-ion velocity vector correlation method. The potential energy curves for the dissociation of the N-N bond were computed within ab initio multireference wave functions based methods (CASSCF and CASPT2) for the first electronic states of N2O 4 and N2O4

Theoretical study of the electronic excited states in ultrathin ionic layers supported on metal surfaces: NaCl/Cu(111)

We present a theoretical study of the electronic excited states in ultrathin ionic layers supported on metal surfaces. We have studied 1, 2, 3, and 4 monolayers of NaCl on a Cu(111) surface. Energies, lifetimes, and associated wave functions of the excited states have been obtained with a joint, model potential–wave packet propagation approach. The excited state with the lowest energy has the character of an image potential state repelled from the surface by the NaCl layer. The next two states present a mixed character of image potential states and NaCl layer states corresponding to the quantization of the conduction band in the finite-size layer. We discuss the role of the layer thickness in decoupling these states from the metal surface and how it affects their lifetimeS.D.-T. gratefully acknowledges postdoctoral support from the Triangle de la Physique and the Juan de la Cierva program from the Spanish Ministerio de Ciencia e Innovación

Unveiling the anisotropic behavior of ultrafast electron transfer at the metal/organic interface

Ultrafast electron transfer between adsorbed organic molecules and metal substrates is studied. In particular, the dynamics of the active electron in the nitroethylene anion/metal-copper surface system has been followed in real time using a wave packet propagation approach, allowing a rigorous analysis of the decay of molecule-localized electronic resonances. We find that the strong coupling with the metal substrate leads to an extremely short lifetime (~1fs) of the π∗ molecular resonance. Comparison between the free-electron metal, Cu(1 0 0), and Cu(1 1 1) surfaces demonstrates that the electronic band structure of the substrate and the shape of the decaying molecular orbital lead to a highly marked anisotropy of the metal continuum states populated by resonant electron transfer from the adsorbate. This finding points at possible anisotropy effects in adsorbate–adsorbate interactions and it is of particular importance in molecular self assembly at metal surfaces, thus opening the way to a rational design of hybrid metal/organic interfaces with tailored electronic propertiesThis work was partially supported by the MICINN - Spanish Ministry of Science and Innovation - projects CTQ2016-76061-P and PID2019-110091 GB-I00, and the ‘María de Maeztu’ (CEX2018- 000805-M) Program for Centers of Excellence in R&

Ultrafast dynamics of electronic resonances in molecules adsorbed on metal surfaces: a wave packet propagation approach

We present a wave packet propagation-based method to study the electron dynamics in molecular species in the gas phase and adsorbed on metal surfaces. It is a very general method that can be employed to any system where the electron dynamics is dominated by an active electron and the coupling between the discrete and continuum electronic states is of importance. As an example, one can consider resonant molecule-surface electron transfer or molecular photoionization. Our approach is based on a computational strategy allowing incorporating ab initio inputs from quantum chemistry methods, such as density functional theory, Hartree-Fock, and coupled cluster. Thus, the electronic structure of the molecule is fully taken into account. The electron wave function is represented on a three-dimensional grid in spatial coordinates, and its temporal evolution is obtained from the solution of the time-dependent Schrödinger equation. We illustrate our method with an example of the electron dynamics of anionic states localized on organic molecules adsorbed on metal surfaces. In particular, we study resonant charge transfer from the I orbitals of three vinyl derivatives (acrylamide, acrylonitrile, and acrolein) adsorbed on a Cu(100) surface. Electron transfer between these lowest unoccupied molecular orbitals and the metal surface is extremely fast, leading to a decay of the population of the molecular anion on the femtosecond timescale. We detail how to analyze the time-dependent electronic wave function in order to obtain the relevant information on the system: The energies and lifetimes of the molecule-localized quasistationary states, their resonant wavefunctions, and the population decay channels. In particular, we demonstrate the effect of the electronic structure of the substrate on the energy and momentum distribution of the hot electrons injected into the metal by the decaying molecular resonanceThis work was partially supported by the MICINN-Spanish Ministry of Science and Innovation-projects CTQ2016-76061-P and PID2019-110091GBI00 and the “María de Maeztu” (CEX2018-000805-M) Program for Centers of Excellence in R&

Catalytic asymmetric synthesis of diazabicyclo[3.1.0]hexanes by 1,3-dipolar cycloaddition of azomethine ylides with azirines

Substituted 1,3-diazabicyclo[3.1.0]hexanes with two contiguous quaternary stereocentres are readily prepared by catalytic asymmetric [3+2] cycloaddition of α-substituted iminoesters with azirines. High diastereoselectivities and enantioselectivities (up to 98% ee) are achieved using CuI/(R)-Fesulphos as the catalytic systemWe thank the Spanish Ministerio de Economía, Industria y Competitividad (Grant CTQ2015-66954-P, MINECO/FEDER, UE) and FEDER/Ministerio de Ciencia, Innovación y Universidades – Agencia Estatal de Investigación (Grant PGC2018-098660-B-I00) for financial suppor

Intramolecular and intermolecular hole delocalization rules the reducer character of isolated nucleobases and homogeneous single-stranded DNA

The use of DNA strands as nanowires or electrochemical biosensors requires a deep understanding of charge transfer processes along the strand, as well as of the redox properties. These properties are computationally assessed in detail throughout this study. By applying molecular dynamics and hybrid QM/continuum and QM/QM/continuum schemes, the vertical ionization energies, adiabatic ionization energies, vertical attachment energies, one-electron oxidation potentials, and delocalization of the hole generated upon oxidation have been determined for nucleobases in their free form and as part of a pure single-stranded DNA. We show that the reducer ability of the isolated nucleobases is explained by the intramolecular delocalization of the positively charged hole, while the enhancement of the reducer character when going from aqueous solution to the strand correlates very well with the intermolecular hole delocalization. Our simulations suggest that the redox properties of DNA strands can be tuned by playing with the balance between intramolecular and intermolecular charge delocalizationThis work was partially supported by the MICINN – Spanish Ministry of Science and Innovation – Projects PID2019-110091GB-I00 and PID2020-117806GA-I00 funded by MCIN/AEI/10.13039/501100011033, and the ‘María de Maeztu’ (CEX2018-000805-M) Program for Centers of Excellence in R & D. J. J. N. acknowledge the Comunidad de Madrid for funding through the Attraction of Talent Program (Grant ref.2018-T1/BMD-10261). J. L. T. acknowledges the FPU19/02292 grant from the Spanish Ministry of Universit

An Efficient Multilayer Approach to Model DNA-Based Nanobiosensors

In this work, we present a full computational protocol to successfully obtain the one-electron reduction potential of nanobiosensors based on a self-assembled monolayer of DNA nucleobases linked to a gold substrate. The model is able to account for conformational sampling and environmental effects at a quantum mechanical (QM) level efficiently, by combining molecular mechanics (MM) molecular dynamics and multilayer QM/MM/continuum calculations within the framework of Marcus theory. The theoretical model shows that a guanine-based biosensor is more prone to be oxidized than the isolated nucleobase in water due to the electrostatic interactions between the assembled guanine molecules. In addition, the redox properties of the biosensor can be tuned by modifying the nature of the linker that anchor the nucleobases to the metal supportThis work was partially supported by the MICINN − Spanish Ministry of Science and Innovation − Project Nos. PID2019-110091GB-I00 and PID2020-117806GA-I00, funded by MCIN/AEI/10.13039/ 501100011033, and the “María de Maeztu” (No. CEX2018- 000805-M) Program for Centers of Excellence in R&D. J.J.N. acknowledge the Comunidad de Madrid for funding through the Attraction of Talent Program (Grant Ref. No. 2018-T1/ BMD-10261). J.L.T. acknowledges the FPU-2019 grant from the Spanish Ministry of Universit

Revealing the Interplay Between Covalent and Non-Covalent Interactions Driving the Adsorption of Monosubstituted Thiourea Derivatives on the Au(111) Surface

“This document is the Accepted Manuscript version of a Published Work that appeared in final form in The Journal of Physical Chemistry C, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see: https://pubs.acs.org/doi/10.1021/acs.jpcc.0c00729This work reports a detailed study of the adsorption of thiourea and seven monosubstituted thiourea derivatives on the Au(111) surface based on self-consistent periodic density functional theory (DFT) calculations. We included in our analysis the most stable cis and trans configurations for each considered monosubstituted derivative. Different functional groups have been selected for the derivatives in order to address the electron-donating/withdrawing effect on the strength of the molecule–metal interaction. The comparison of the cis- and trans-derivatives revealed interactions of different nature between the molecules and the Au(111) surface. We have been able to disentangle these interactions analyzing the charge density difference plots, the projected density of states (pDOS) and the Non-Covalent Interactions (NCI). For the non-substituted thiourea and all the studied derivatives, besides the strong S–Au bond, it has been observed an Au···H–N interaction similar to a hydrogen bonding, which is caused by the charge transfer from the molecules to the Au(111) surface inducing a charge counterbalancing: Auδ−Hδ+Nδ−. Furthermore, π–Au interactions between the functional group of the derivatives and the Au(111) surface, mainly observed for the cis-derivatives, were highlighted by the NCI plots. In some particular cases it was also possible to distinguish long-range interactions of the type lone pair–Au. The present results provide insight into a new kind of organic molecule–metal surface interaction, opening the way for the synthesis of potential nanodevices with diverse applications such as sensing (biosensors or atmospheric sensors), optoelectronics, pollution control, or energy conversionThis work was partially supported by the “Proyecto Nacional de Ciencias Básicas”, Cuba Code P223LH001-079 “Absorción de moléculas organosulfuradas en superficies métalicas” and by Project CTQ2016-76061-P of the Spanish Ministry of Science and Innovation. S.D.-T. acknowledges financial support from the Spanish Ministry of Science and Innovation, through the “María de Maeztu” Programme for Units of Excellence in R&D (CEX2018-000805-M). M.P.H. would like to thank DGAPAUNAM for a 4-month fellowship through Programa de Estancias de Investigación en la UNAM (PREI