J Phys Chem A
March 2024
Scuola Superiore Meridionale, Largo San Marcellino 10, I-80138 Napoli, Italy.
Modern, nonlinear, time-resolved spectroscopic techniques have opened new doors for investigating the intriguing but complex world of photoinduced ultrafast out-of-equilibrium phenomena and charge dynamics. The interaction between light and matter introduces an additional dimension, where the complex interplay between electronic and vibrational dynamics needs the most advanced theoretical-computational protocols to be fully understood on the molecular scale. In this study, we showcase the capabilities of ab initio molecular dynamics simulation integrated with a multiresolution wavelet protocol to carefully investigate the excited-state relaxation dynamics in a noncovalent complex involving tetramethylbenzene (TMB) and tetracyanoquinodimethane (TCNQ) undergoing charge transfer (CT) upon photoexcitation.
View Article and Find Full Text PDFJ Chem Theory Comput
November 2023
Scuola Normale Superiore di Pisa, Piazza dei Cavalieri 7, I-56126 Pisa, Italy.
An enhanced computational protocol has been devised for the accurate characterization of gas-phase barrier-less reactions in the framework of the reaction-path (RP) and variable reaction coordinate variational transition-state theory. In particular, the synergistic combination of density functional theory and Monte Carlo sampling to optimize reactive fluxes led to a reliable yet effective computational workflow. A black-box strategy has been developed for selecting the most suited density functional with reference to a high-level one-dimensional reference potential.
View Article and Find Full Text PDFJ Comput Chem
February 2024
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, Naples, Italy.
Photo-induced charge transfer (CT) states are pivotal in many technological and biological processes. A deeper knowledge of such states is mandatory for modeling the charge migration dynamics. Real-time time-dependent density functional theory (RT-TD-DFT) electronic dynamics simulations are employed to explicitly observe the electronic density time-evolution upon photo-excitation.
View Article and Find Full Text PDFMolecules
April 2023
Scuola Superiore Meridionale, Largo San Marcellino 10, I-80138 Napoli, Italy.
Electronic properties and absorption spectra are the grounds to investigate molecular electronic states and their interactions with the environment. Modeling and computations are required for the molecular understanding and design strategies of photo-active materials and sensors. However, the interpretation of such properties demands expensive computations and dealing with the interplay of electronic excited states with the conformational freedom of the chromophores in complex matrices (i.
View Article and Find Full Text PDFNanomaterials (Basel)
March 2023
Dipartimento di Ingegneria Chimica, dei Materiali e della Produzione Industriale, Università degli Studi di Napoli Federico II, P.le Tecchio, 80, I-80125 Napoli, Italy.
Stimulated Raman scattering in transparent glass-ceramics (TGCs) based on bulk nucleating phase BaNaNbO were investigated with the aim to explore the influence of micro- and nanoscale structural transformations on Raman gain. Nanostructured TGCs were synthesized, starting with 8BaO·15NaO·27NbO·50SiO (BaNaNS) glass, by proper nucleation and crystallization heat treatments. TGCs are composed of nanocrystals that are 10-15 nm in size, uniformly distributed in the residual glass matrix, with a crystallinity degree ranging from 30 up to 50% for samples subjected to different heat treatments.
View Article and Find Full Text PDFJACS Au
January 2023
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia 21, I-80126 Napoli, Italy.
Charge-transfer dynamics and interligand electron transfer (ILET) phenomena play a pivotal role in dye-sensitizers, mostly represented by the Ru-based polypyridyl complexes, for TiO and ZnO-based solar cells. Starting from metal-to-ligand charge-transfer (MLCT) excited states, charge dynamics and ILET can influence the overall device efficiency. In this letter, we focus on N3 dye ( [Ru(dcbpy)(NCS)], dcbpy = 4,4'-dicarboxy-2,2'-bipyridine) to provide a first direct observation with high time resolution (<20 fs) of the ultrafast electron exchange between bpy-like ligands.
View Article and Find Full Text PDFJ Chem Theory Comput
January 2023
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia 21, I-80126, Napoli, Italy.
Photoinduced charge transfer (CT) excited states and their relaxation mechanisms can be highly interdependent on the environment effects and the consequent changes in the electronic density. Providing a molecular interpretation of the ultrafast (subpicosecond) interplay between initial photoexcited states in such dense electronic manifolds in condensed phase is crucial for improving and understanding such phenomena. Real-time time-dependent density functional theory is here the method of choice to observe the charge density, explicitly propagated in an ultrafast time domain, along with all time-dependent properties that can be easily extracted from it.
View Article and Find Full Text PDFInt J Mol Sci
December 2022
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, Via Cintia 21, I-80126 Napoli, Italy.
Fluorescent Proteins are widely studied for their multiple applications in technological and biotechnological fields. Despite this, they continue to represent a challenge in terms of a complete understanding of all the non-equilibrium photo-induced processes that rule their properties. In this context, a theoretical-computational approach can support experimental results in unveiling and understanding the processes taking place after electronic excitation.
View Article and Find Full Text PDFNat Commun
November 2022
Istituto Nazionale di Ottica, Consiglio Nazionale delle Ricerche, Via Campi Flegrei 34, Pozzuoli, 80078, Italy.
By reducing both the internal and translational temperature of any species down to a few kelvins, the buffer-gas-cooling (BGC) technique has the potential to dramatically improve the quality of ro-vibrational molecular spectra, thus offering unique opportunities for transition frequency measurements with unprecedented accuracy. However, the difficulty in integrating metrological-grade spectroscopic tools into bulky cryogenic equipment has hitherto prevented from approaching the kHz level even in the best cases. Here, we overcome this drawback by an original opto-mechanical scheme which, effectively coupling a Lamb-dip saturated-absorption cavity ring-down spectrometer to a BGC source, allows us to determine the absolute frequency of the acetylene (ν + ν) R(1)e transition at 6561.
View Article and Find Full Text PDFJ Phys Chem A
December 2022
Dipartimento di Chimica "Ugo Schiff", Università degli Studi di Firenze, Via della Lastruccia 3, Sesto FiorentinoI-50019, Italy.
A detailed understanding and interpretation of absorption spectra of molecular systems, especially in condensed phases, requires computational models that allow their structural and electronic features to be connected to the observed macroscopic spectra. This work is focused on modeling the electronic absorption spectrum of a fluorescent probe, namely, the 9-(4-((bis(2-((2-(ethylthio)ethyl)thio)ethyl)amino)methyl)phenyl)-6-(pyrrolidin-1-yl)-3-xanthen-3-one molecule, depicted by a combined classical-quantum chemical approach. Particularly, first classical molecular dynamics (MD) has been used to explore the configurational space, and next, the absorption spectrum has been reconstructed by averaging the results of time-dependent density functional theory (TD-DFT) calculations performed on equispaced molecular conformations extracted from MD to properly sample the configurational space explored at finite temperature.
View Article and Find Full Text PDFJ Phys Chem A
September 2022
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, 80126 Napoli, Italy.
The interplay between light absorption and the molecular environment has a central role in the observed photophysics of a wide range of photoinduced chemical and biological phenomena. The understanding of the interplay between vibrational and electronic transitions is the focus of this work, since it can provide a rationale to tune the optical properties of charge transfer (CT) materials used for technological applications. A clear description of these processes poses a nontrivial challenge from both the theoretical and experimental points of view, where the main issue is how to accurately describe and probe drastic changes in the electronic structure and the ultrafast molecular relaxation and dynamics.
View Article and Find Full Text PDFCells
January 2022
Department of Molecular Medicine and Medical Biotechnology, University of Naples "Federico II", Via S. Pansini 5, 80131 Naples, Italy.
To fight neurodegenerative diseases, several therapeutic strategies have been proposed that, to date, are either ineffective or at the early preclinical stages. Intracellular protein aggregates represent the cause of about 70% of neurodegenerative disorders, such as Alzheimer's disease. Thus, autophagy, i.
View Article and Find Full Text PDFJ Chem Theory Comput
March 2022
Chimie ParisTech-PSL, CNRS, Institute of Chemistry for Health and Life Sciences, F-75005 Paris, France.
By coupling an enhanced sampling algorithm with an orbital-localized variant of Car-Parrinello molecular dynamics, the so-called atomic centered density matrix propagation model, we reconstruct the free energy profiles along reaction pathways using different density functional approximations (DFAs) ranging from locals to hybrids. In particular, we compare the computed free energy barrier height of proton transfer (PT) reactions to those obtained by a more traditional static approach, based on the intrinsic reaction coordinate (IRC), for two case systems, namely malonaldehyde and formic acid dimer. The obtained results show that both the IRC profiles and the potentials of mean force, derived from biased dynamic trajectories, are very sensitive to the density functional approximation applied.
View Article and Find Full Text PDFPhys Chem Chem Phys
October 2021
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia 21, I-80126, Napoli, Italy.
Environmental effects can drastically influence the optical properties and photoreactivity of molecules, particularly in the presence of polar and/or protic solvents. In this work we investigate a negatively charged Ru(II) complex, [Ru(dcbpy)(NCS)] [dcbpy = (4,4'-dicarboxy-2,2'-bipyridine)], in water solution, since this system belongs to a broader class of transition-metal compounds undergoing upon photo-excitation rapid and complex charge transfer (CT) dynamics, which can be dictated by structural rearrangement and solvent environment. molecular dynamics (AIMD) relying on a hybrid quantum/molecular mechanics scheme is used to probe the equilibrium microsolvation around the metal complex in terms of radial distribution functions of the main solvation sites and solvent effects on the overall equilibrium structure.
View Article and Find Full Text PDFJ Phys Chem B
September 2021
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy.
Chem Sci
April 2021
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo via Cintia Napoli 80126 Italy
We present electronic structure methods to unveil the non-radiative pathways of photoinduced charge transfer (CT) reactions that play a main role in photophysics and light harvesting technologies. A prototypical π-stacked molecular complex consisting of an electron donor (1-chloronaphthalene, 1ClN) and an electron acceptor (tetracyanoethylene, TCNE) was investigated in dichloromethane solution for this purpose. The characterization of TCNE:π:1ClN in both its equilibrium ground and photoinduced low-lying CT electronic states was performed by using a reliable and accurate theoretical-computational methodology exploiting molecular dynamics simulations.
View Article and Find Full Text PDFEntropy (Basel)
May 2021
P.N. Lebedev Physical Institute, 119991 Moscow, Russia.
The tomography of a single quantum particle (i.e., a quantum wave packet) in an accelerated frame is studied.
View Article and Find Full Text PDFJ Phys Chem A
May 2021
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy.
Int J Mol Sci
December 2020
Consiglio Nazionale delle Ricerche-Istituto Nazionale di Ottica, Via Campi Flegrei 34, 80078 Pozzuoli, Italy.
We review the recent developments in precision ro-vibrational spectroscopy of buffer-gas-cooled neutral molecules, obtained using infrared frequency combs either as direct probe sources or as ultra-accurate optical rulers. In particular, we show how coherent broadband spectroscopy of complex molecules especially benefits from drastic simplification of the spectra brought about by cooling of internal temperatures. Moreover, cooling the translational motion allows longer light-molecule interaction times and hence reduced transit-time broadening effects, crucial for high-precision spectroscopy on simple molecules.
View Article and Find Full Text PDFJ Phys Chem Lett
November 2020
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia, I-80126 Napoli, Italy.
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 simulation of the whole decay pathways of a recently proposed artificial molecular reaction center.
View Article and Find Full Text PDFJ Chem Theory Comput
November 2020
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, via Cintia, I-80126 Napoli, Italy.
Phys Chem Chem Phys
October 2020
Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M. S. Angelo, Via Cintia, I-80126 Napoli, Italy.
Vibrational analysis in solution and the theoretical determination of infrared and Raman spectra are of key importance in many fields of chemical interest. Vibrational band dynamics of molecules and their sensitivity to the environment can also be captured by these spectroscopies in their time dependent version. However, it is often difficult to provide an interpretation of the experimental data at the molecular scale, such as molecular mechanisms or the processes hidden behind them.
View Article and Find Full Text PDFJ Chem Theory Comput
October 2020
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M. S. Angelo, via Cintia, I-80126 Napoli, Italy.
We present a novel time-resolved vibrational analysis for studying photoinduced nuclear relaxation. Generalized modes velocities are defined from ab initio molecular dynamics and wavelet transformed, providing the time localization of vibrational signals in the electronic excited state. The photoexcited pyranine in aqueous solution is presented as a case study.
View Article and Find Full Text PDFJ Comput Chem
October 2020
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S. Angelo, Naples, Italy.
Solute-solvent interactions are proxies for understanding how the electronic density of a chromophore interacts with the environment in a more exhaustive way. The subtle balance between polarization, electrostatic, and non-bonded interactions need to be accurately described to obtain good agreement between simulations and experiments. First principles approaches providing accurate configurational sampling through molecular dynamics may be a suitable choice to describe solvent effects on solute chemical-physical properties and spectroscopic features, such as optical absorption of dyes.
View Article and Find Full Text PDFJ Comput Chem
July 2020
Dipartimento di Scienze Chimiche, Università di Napoli Federico II, Complesso Universitario di M.S.Angelo, Napoli, Italy.