Latest Publications

DOI: 10.1002/qua.26560

International Journal of Quantum Chemistry

In this work, we investigate the effects of different atomic charge and nonelectrostatic models on the hydration energies of neutral molecules, using an implicit solvation model. The solvation free energy is divided into two main components, the first resulting from a self‐consistent reaction field treatment of the bulk electrostatics obtained by solving the Poisson equation in a finite‐difference (FD) approach where the solute charge density is approximated by atomic charges, the second corresponding to short‐range interactions between the solute and the solvent in the first solvation shell. Five different atomic charge models (Mulliken, Hirshfeld, Hirshfeld‐I, CM5 and its iterative version, CM5‐I) have been considered, both at the Hartree–Fock (HF) and B3LYP levels, with three different basis sets, alongside two nonelectrostatic models including the cavity, dispersion, and solvent structural effects (CDS) model. Averagin...

The Journal of Physical Chemistry Letters

DOI: 10.1021/acs.jpclett.0c02766

The development of efficient artificial leaves relies on the subtle combination of molecular assemblies able to absorb sunlight, converting light energy into electrochemical potential energy and finally transducing it into accessible chemical energy. The electronic design of these charge transfer molecular machines is crucial to build a complex supramolecular architecture for the light energy conversion. Here, we present an ab initio simulation of the whole decay pathways of a recently proposed artificial molecular reaction center. A complete structural and energetic characterization has been carried out with methods based on density functional theory, its time-dependent version, and a broken-symmetry approach. On the basis of our findings we provide a revision of the pathway only indirectly postulated from an experimental point of view, along with unprecedented and significant insights on the electronic and nucle...

DOI:10.1039/D0CP03038D

Journal of Physical Chemistry Chemical Physics

The field of organic photovoltaics has witnessed a steady growth in the last decades and a recent renewal with the blossom of single-material organic solar cells (SMOSCs). Nonetheless, due to the intrinsic complexity of these devices (both in terms of their size and of the condensed phases involved), computational approaches enabling to accurately predict their geometrical and electronic structure and to link their microscopic properties to the observed macroscopic behaviour are still lacking. In this work, we have focused on the rationalization of transport dynamics and we have setup a computational approach that makes a combined use of classical simulations and Density Functional Theory with the aim of disclosing the most relevant electronic and structural features of dyads used for SMOC applications. As prototype dyad we have considered a molecule that consists in a dithiafulvalene-functionalized diketopyrrolopyrrol...

Macromolecular Rapid Comunication

DOI: 10.1002/marc.202000426

The perylene bisimide derivative Paliogen Black (P‐black) is proposed as a new chromogenic probe that shows visible (vis) and near‐infrared (NIR) responses after mechanical solicitations of host linear low‐density polyethylene (LLDPE) films. P‐black is reported to display strong absorption in the vis spectrum and unusual reflective and cooling features in the NIR region. Uniaxial deformation of the 2.5, 5, and 10 wt% P‐black/LLDPE films yields a dichroic absorption under polarized light with color variations attributed by the computational analysis to the distinct anisotropic behavior of the transition dipole moments of P‐black chromophores. When LLDPE films are deformed, P‐black aggregates reduce their size from ≈30–40 µm to ≈5–10 µm that, in turn, causes reflectivity losses of about 30–40% at the maximum elongation. This gives rise to warming of 5–6 °C of the locally oriented film placed in contact with a black substrate und...

Chemistry A European Journal

DOI: 10.1002/chem.202002696

A formal [3+2] cyclization mediated by silver(I) oxide  and DBU is described herein. Through a broad variety of carbonyl compounds, this system can promote cyclization reactions with high yield (up to 85%) and diastereoselectivity (up to 95:5) for a straightforward access to complex and congested dihydrofuran derivatives in one step using smooth conditions. Based on DFT studies, the proposed mechanism would involve an allenyl silver intermediate.

Journal of Chemical Theory and Computation

DOI: 10.1021/acs.jctc.0c00762

Photonastic materials present a directional and repeatable deformation of the material shape due to transduction from light energy to mechanical energy. Among these materials, light-responsive polymers, composed of photochromic molecules embedded in a polymer matrix, are of high interest. The present work aims at laying the foundation stone of the modeling of the photomechanical behavior of such systems by proposing a computational strategy that is able to investigate (i) the impact of the polymer matrix on the photochromic properties of a dithienylethene (DTE) switch and (ii) the impact of the photochromic reaction on the polymer environment. Contrary to previous approaches, the present model is able to propose a realistic arrangement of the photochrome embedded in the polymer film, thanks to the adaptation of the so-called “controlled-like polymerization algorithm” [Lemarchand, C. A.; J. Chem. Phys. 2019, 50, 2249...

Organometallics

DOI: 10.1021/acs.organomet.0c00309

While 31P NMR is a major technique to characterize phosphine-ligated transition-metal complexes—which are ubiquitous in catalysis—31P NMR chemical shifts are difficult to predict using empirical rules or tabulated data. Aiming at filling this gap, we propose here guidelines enabling their prediction at a modest computational cost. Rooted in density functional theory, our protocol features structural optimization and magnetic shielding tensor calculations performed at a global hybrid level using a tailored locally dense basis set. Validation on an experimental data series revealed that while a careful conformational analysis is required in the case of flexible phosphines, the use of the free ligand or another complex as a reference for chemical shifts often allows solving this drawback. Applicability to various diamagnetic complexes of first-row transition metals is demonstrated, including large systems relevant to contemporary catalysis.

Dyes and Pigments

DOI: 10.1016/j.dyepig.2020.108661

In the colorful world of pigments and dyes, the chemical reduction of chromophores usually leads to bleaching because of π-conjugation interruption. Yet, the natural phenoxazinone-based ommochrome pigment called xanthommatin displays a bathochromic (i.e. red) shift upon two-electron reduction to its corresponding phenoxazine, whose electronic origins are not completely disclosed. In this study, we investigated, at quantum chemical level, a series of phenoxazinone/phenoxazine pairs that was previously explored by UV–Vis spectroscopy (Schäfer and Geyer, 1972), and which displays different hypsochromic and bathochromic shifts upon reduction. Density Functional Theory (DFT) and Time Dependent DFT (TDDFT) have been applied to compute their optical properties in order to find a rational explanation of the observed photophysical behavior. Based on our results, we propose that the electro-accepting power of auxochromes and their conjugation fac...

DOI:10.1002/jcc.26224

Journal of Computational Chemistry

Electrons and protons are the main actors in play in proton coupled electron transfer (PCET) reactions, which are fundamental in many biological (i.e., photosynthesis and enzymatic reactions) and electrochemical processes. The mechanism, energetics and kinetics of PCET reactions are strongly controlled by the coupling between the transferred electrons and protons. Concerted PCET reactions are classified according to the electronical adiabaticity degree of the process. To discriminate among different mechanisms, we propose a new analysis based on the use of electron density based indexes. We choose, as test case, the 3‐Methylphenoxyl/phenol system in two different conformations to show how the proposed analysis is a suitable tool to discriminate between the different degree of adiabaticity of PCET processes. The very low computational cost of this procedure is extremely promising to analyze and provide evidences of PCET mechanisms r...

Journal of Chemical Theory and Computation

DOI: 10.1021/acs.jctc.0c00296

We present a new formula and implementation for a descriptor enabling quantification of the electron–hole distance associated with a charge transfer of an optical transition, on the basis of the knowledge of the densities of the electronic ground and excited states. This index is able to define a charge-transfer length even for systems that would be otherwise difficult to treat, like symmetric molecules, while maintaining a very low computational cost and the possibility to be coupled to any method providing ground and excited state electron densities. After a benchmark of its performance on a series of push–pull molecules, the index has been applied to a set of large symmetric luminophores, the so-called “butterfly molecules”, showing promising applications in optoelectronics, to highlight its potential use in the design of new compounds.

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