1
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Perrella F, Coppola F, Rega N, Petrone A. An Expedited Route to Optical and Electronic Properties at Finite Temperature via Unsupervised Learning. Molecules 2023; 28:molecules28083411. [PMID: 37110644 PMCID: PMC10144358 DOI: 10.3390/molecules28083411] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2023] [Revised: 04/06/2023] [Accepted: 04/07/2023] [Indexed: 04/29/2023] Open
Abstract
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.e., solvents, biomolecules, crystals) at finite temperature. Computational protocols combining time dependent density functional theory and ab initio molecular dynamics (MD) have become very powerful in this field, although they require still a large number of computations for a detailed reproduction of electronic properties, such as band shapes. Besides the ongoing research in more traditional computational chemistry fields, data analysis and machine learning methods have been increasingly employed as complementary approaches for efficient data exploration, prediction and model development, starting from the data resulting from MD simulations and electronic structure calculations. In this work, dataset reduction capabilities by unsupervised clustering techniques applied to MD trajectories are proposed and tested for the ab initio modeling of electronic absorption spectra of two challenging case studies: a non-covalent charge-transfer dimer and a ruthenium complex in solution at room temperature. The K-medoids clustering technique is applied and is proven to be able to reduce by ∼100 times the total cost of excited state calculations on an MD sampling with no loss in the accuracy and it also provides an easier understanding of the representative structures (medoids) to be analyzed on the molecular scale.
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Affiliation(s)
- Fulvio Perrella
- Scuola Superiore Meridionale, Largo San Marcellino 10, I-80138 Napoli, Italy
| | - Federico Coppola
- Scuola Superiore Meridionale, Largo San Marcellino 10, I-80138 Napoli, Italy
| | - Nadia Rega
- Scuola Superiore Meridionale, Largo San Marcellino 10, I-80138 Napoli, Italy
- Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia 21, I-80126 Napoli, Italy
- Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di M.S. Angelo ed. 6, via Cintia 21, I-80126 Napoli, Italy
| | - Alessio Petrone
- Scuola Superiore Meridionale, Largo San Marcellino 10, I-80138 Napoli, Italy
- Department of Chemical Sciences, University of Napoli Federico II, Complesso Universitario di M.S. Angelo, via Cintia 21, I-80126 Napoli, Italy
- Istituto Nazionale di Fisica Nucleare, Sezione di Napoli, Complesso Universitario di M.S. Angelo ed. 6, via Cintia 21, I-80126 Napoli, Italy
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2
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Falbo E, Fusè M, Lazzari F, Mancini G, Barone V. Integration of Quantum Chemistry, Statistical Mechanics, and Artificial Intelligence for Computational Spectroscopy: The UV-Vis Spectrum of TEMPO Radical in Different Solvents. J Chem Theory Comput 2022; 18:6203-6216. [PMID: 36166322 PMCID: PMC9558374 DOI: 10.1021/acs.jctc.2c00654] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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The ongoing integration of quantum chemistry, statistical
mechanics,
and artificial intelligence is paving the route toward more effective
and accurate strategies for the investigation of the spectroscopic
properties of medium-to-large size chromophores in condensed phases.
In this context we are developing a novel workflow aimed at improving
the generality, reliability, and ease of use of the available computational
tools. In this paper we report our latest developments with specific
reference to unsupervised atomistic simulations employing non periodic
boundary conditions (NPBC) followed by clustering of the trajectories
employing optimized feature spaces. Next accurate variational computations
are performed for a representative point of each cluster, whereas
intracluster fluctuations are taken into account by a cheap yet reliable
perturbative approach. A number of methodological improvements have
been introduced including, e.g., more realistic reaction field effects
at the outer boundary of the simulation sphere, automatic definition
of the feature space by continuous perception of solute–solvent
interactions, full account of polarization and charge transfer in
the first solvation shell, and inclusion of vibronic contributions.
After its validation, this new approach has been applied to the challenging
case of solvatochromic effects on the UV–vis spectra of a prototypical
nitroxide radical (TEMPO) in different solvents. The reliability,
effectiveness, and robustness of the new platform is demonstrated
by the remarkable agreement with experiment of the results obtained
through an unsupervised approach characterized by a strongly reduced
computational cost as compared to that of conventional quantum mechanics
and molecular mechanics models without any accuracy reduction.
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Affiliation(s)
- Emanuele Falbo
- Scuola Normale Superiore di Pisa, piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Marco Fusè
- Scuola Normale Superiore di Pisa, piazza dei Cavalieri 7, 56126 Pisa, Italy.,Dipartimento di Medicina Molecolare e Traslazionale, Università di Brescia, Viale Europa 11, 25123 Brescia, Italy
| | - Federico Lazzari
- Scuola Normale Superiore di Pisa, piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Giordano Mancini
- Scuola Normale Superiore di Pisa, piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore di Pisa, piazza dei Cavalieri 7, 56126 Pisa, Italy
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3
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Del Galdo S, Chiarini M, Casieri C, Daidone I. High density water clusters observed at high concentrations of the macromolecular crowder PEG400. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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4
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Franco LR, Toledo KCF, Matias TA, Benavides PA, Cezar HM, Araujo CM, Coutinho K, Araki K. Unraveling the acid-base characterization and solvent effects on the structural and electronic properties of a bis-bidentate bridging ligand. Phys Chem Chem Phys 2022; 24:10222-10240. [PMID: 35420602 DOI: 10.1039/d1cp03912a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Understanding the interactions and the solvent effects on the distribution of several species in equilibrium and how it can influence the 1H-NMR properties, spectroscopy (UV-vis absorption), and the acid-base equilibria can be especially challenging. This is the case of a bis-bidentate bridging ligand bis(2-pyridyl)-benzo-bis(imidazole), where the two pyridyl and four imidazolyl nitrogen atoms can be protonated in different ways, depending on the solvent, generating many isomeric/tautomeric species. Herein, we report a combined theoretical-experimental approach based on a sequential quantum mechanics/molecular mechanics procedure that was successfully applied to describe in detail the acid-base characterization and its effects on the electronic properties of such a molecule in solution. The calculated free-energies allowed the identification of the main species present in solution as a function of the solvent polarity, and its effects on the magnetic shielding of protons (1H-NMR chemical shifts), the UV-vis absorption spectra, and the acid-base equilibrium constants (pKas) in aqueous solution. Three acid-base equilibrium constants were experimentally/theoretically determined (pKa1 = 1.3/1.2, pKa2 = 2.1/2.2 and pKa5 = 10.1/11.3) involving mono-deprotonated and mono-protonated cis and trans species. Interestingly, other processes with pKa3 = 3.7 and pKa4 = 6.0 were also experimentally determined and assigned to the protonation and deprotonation of dimeric species. The dimerization of the most stable neutral species was investigated by Monte Carlo simulations and its electronic effects were considered for the elucidation of the UV-vis absorption bands, revealing transitions mainly with the charge-transfer characteristic and involving both the monomeric species and the dimeric species. The good matching of the theoretical and experimental results provides an atomistic insight into the solvent effects on the electronic properties of this bis-bidentate bridging ligand.
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Affiliation(s)
- Leandro Rezende Franco
- Instituto de Física, Universidade de São Paulo, Cidade Universitária, 05508-090 São Paulo, SP, Brazil. .,Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden
| | | | - Tiago Araujo Matias
- Instituto de Química, Universidade de São Paulo, Av. Lineu Prestes 748, Butantã, 05508-000 São Paulo, SP, Brazil.
| | - Paola Andrea Benavides
- Instituto de Química, Universidade de São Paulo, Av. Lineu Prestes 748, Butantã, 05508-000 São Paulo, SP, Brazil.
| | - Henrique Musseli Cezar
- Instituto de Física, Universidade de São Paulo, Cidade Universitária, 05508-090 São Paulo, SP, Brazil.
| | - C Moyses Araujo
- Department of Engineering and Physics, Karlstad University, 65188 Karlstad, Sweden.,Materials Theory Division, Department of Physics and Astronomy, Ångström Laboratory, Uppsala University, 75120 Uppsala, Sweden
| | - Kaline Coutinho
- Instituto de Física, Universidade de São Paulo, Cidade Universitária, 05508-090 São Paulo, SP, Brazil.
| | - Koiti Araki
- Instituto de Química, Universidade de São Paulo, Av. Lineu Prestes 748, Butantã, 05508-000 São Paulo, SP, Brazil.
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5
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Barone V, Carnimeo I, Mancini G, Pagliai M. Development, Validation, and Pilot Application of a Generalized Fluctuating Charge Model for Computational Spectroscopy in Solution. ACS OMEGA 2022; 7:13382-13394. [PMID: 35474835 PMCID: PMC9026056 DOI: 10.1021/acsomega.2c01110] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 03/23/2022] [Indexed: 06/14/2023]
Abstract
A general approach enforcing nonperiodic boundary conditions for the computation of spectroscopic properties in solution has been improved including an effective description of charge-transfer contributions and coordination number adjustment for explicit solvent molecules. Both contributions are obtained from a continuous description of intermolecular hydrogen bonds, which has been employed also for an effective clustering of molecular dynamics trajectories. Fine tuning of the model has been performed for several water clusters, and then its efficiency and reliability have been demonstrated by computing the absorption spectra of different creatinine tautomers in aqueous solution.
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Affiliation(s)
- Vincenzo Barone
- Scuola
Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Ivan Carnimeo
- Scuola
Internazionale Superiore di Studi Avanzati, via Bonomea 265, 34136 Trieste, Italy
| | - Giordano Mancini
- Scuola
Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Marco Pagliai
- Dipartimento
di Chimica “Ugo Schiff”, Università
degli Studi di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
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6
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Mancini G, Fusè M, Lipparini F, Nottoli M, Scalmani G, Barone V. Molecular Dynamics Simulations Enforcing Nonperiodic Boundary Conditions: New Developments and Application to the Solvent Shifts of Nitroxide Magnetic Parameters. J Chem Theory Comput 2022; 18:2479-2493. [PMID: 35257572 PMCID: PMC9009096 DOI: 10.1021/acs.jctc.2c00046] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
![]()
Multiscale methods
combining quantum mechanics and molecular mechanics
(QM/MM) have become the most suitable and effective strategies for
the investigation of the spectroscopic properties of medium-to-large
size chromophores in condensed phases. In this context, we are developing
a novel workflow aimed at improving the generality, reliability, and
ease of use of the available computational tools. In this paper, we
report our latest developments with specific reference to a general
protocol based on atomistic simulations, carried out under nonperiodic
boundary conditions (NPBC). In particular, we add to our in house
MD engine a new efficient treatment of mean field electrostatic contributions
to energy and forces, together with the capability of performing the
simulations either in the canonical (NVT) or in the
isothermal–isobaric (NPT) ensemble. Next,
we provide convincing evidence that the NBPC approach enhanced by
specific tweaks for rigid body propagation, allows for the simulation
of solute–solvent systems with a minimum number of degrees
of freedom and large integration time step. After its validation,
this new approach is applied to the challenging case of solvatochromic
effects on the electron paramagnetic resonance (EPR) spectrum of a
prototypical nitroxide radical. To this end, we propose and validate
also an automated protocol to extract and weight simulation snapshots,
making use of a continuous description of the strength of solute–solvent
hydrogen bridges. While further developments are being worked on,
the effectiveness of our approach, even in its present form, is demonstrated
by the accuracy of the results obtained through an unsupervised approach
characterized by a strongly reduced computational cost as compared
to that of conventional QM/MM models, without any appreciable deterioration
of accuracy.
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Affiliation(s)
- Giordano Mancini
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy.,Istituto Nazionale di Fisica Nucleare (INFN) sezione di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
| | - Marco Fusè
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy
| | - Filippo Lipparini
- Dipartimento di Chimica e Chimica Industriale, Universitaá di Pisa, Via G. Moruzzi 13, 56124 Pisa, Italy
| | - Michele Nottoli
- Dipartimento di Chimica e Chimica Industriale, Universitaá di Pisa, Via G. Moruzzi 13, 56124 Pisa, Italy
| | - Giovanni Scalmani
- Gaussian, Inc., 340 Quinnipiac Street, Building 40, Wallingford, Connecticut 06492, United States
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy.,Istituto Nazionale di Fisica Nucleare (INFN) sezione di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
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7
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Fehér PP, Madarász Á, Stirling A. Multiscale Modeling of Electronic Spectra Including Nuclear Quantum Effects. J Chem Theory Comput 2021; 17:6340-6352. [PMID: 34582200 PMCID: PMC8515811 DOI: 10.1021/acs.jctc.1c00531] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Indexed: 11/28/2022]
Abstract
Theoretical prediction of electronic absorption spectra without input from experiments is no easy feat, as it requires addressing all of the factors that affect line shapes. In practice, however, the methodologies are limited to treat these ingredients only to a certain extent. Here, we present a multiscale protocol that addresses the temperature, solvent, and nuclear quantum effects as well as anharmonicity and the reconstruction of the final spectra from individual transitions. First, quantum mechanics/molecular mechanics (QM/MM) molecular dynamics is conducted to obtain trajectories of solute-solvent configurations, from which the corresponding quantum-corrected ensembles are generated through the generalized smoothed trajectory analysis (GSTA). The optical spectra of the ensembles are then produced by calculating vertical transitions using time-dependent density-functional theory (TDDFT) with implicit solvation. To obtain the final spectral shapes, the stick spectra from TDDFT are convoluted with Gaussian kernels where the half-widths are determined by a statistically motivated strategy. We have tested our method by calculating the UV-vis spectra of a recently discovered acridine photocatalyst in two redox states. Vibronic progressions and broadenings due to the finite lifetime of the excited states are not included in the methodology yet. Nuclear quantization affects the relative peak intensities and widths, which is necessary to reproduce the experimental spectrum. We have also found that using only the optimized geometry of each molecule works surprisingly well if a proper empirical broadening factor is applied. This is explained by the rigidity of the conjugated chromophore moieties of the selected molecules, which are mainly responsible for the excitations in the spectra. In contrast, we have also shown that other parts of the molecules are flexible enough to feature anharmonicities that impair the use of other techniques such as Wigner sampling.
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Affiliation(s)
- Péter P. Fehér
- Institute
of Organic Chemistry, Research Centre for
Natural Sciences, Magyar tudósok krt. 2, 1117 Budapest, Hungary
| | - Ádám Madarász
- Institute
of Organic Chemistry, Research Centre for
Natural Sciences, Magyar tudósok krt. 2, 1117 Budapest, Hungary
| | - András Stirling
- Institute
of Organic Chemistry, Research Centre for
Natural Sciences, Magyar tudósok krt. 2, 1117 Budapest, Hungary
- Department
of Chemistry, Eszterházy Károly
University, Leányka
u. 6, 3300 Eger, Hungary
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8
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Barone V, Puzzarini C, Mancini G. Integration of theory, simulation, artificial intelligence and virtual reality: a four-pillar approach for reconciling accuracy and interpretability in computational spectroscopy. Phys Chem Chem Phys 2021; 23:17079-17096. [PMID: 34346437 DOI: 10.1039/d1cp02507d] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The established pillars of computational spectroscopy are theory and computer based simulations. Recently, artificial intelligence and virtual reality are becoming the third and fourth pillars of an integrated strategy for the investigation of complex phenomena. The main goal of the present contribution is the description of some new perspectives for computational spectroscopy, in the framework of a strategy in which computational methodologies at the state of the art, high-performance computing, artificial intelligence and virtual reality tools are integrated with the aim of improving research throughput and achieving goals otherwise not possible. Some of the key tools (e.g., continuous molecular perception model and virtual multifrequency spectrometer) and theoretical developments (e.g., non-periodic boundaries, joint variational-perturbative models) are shortly sketched and their application illustrated by means of representative case studies taken from recent work by the authors. Some of the results presented are already well beyond the state of the art in the field of computational spectroscopy, thereby also providing a proof of concept for other research fields.
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Affiliation(s)
- Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy.
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9
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Segalina A, Cerezo J, Prampolini G, Santoro F, Pastore M. Accounting for Vibronic Features through a Mixed Quantum-Classical Scheme: Structure, Dynamics, and Absorption Spectra of a Perylene Diimide Dye in Solution. J Chem Theory Comput 2020; 16:7061-7077. [DOI: 10.1021/acs.jctc.0c00919] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- Alekos Segalina
- Université de Lorraine & CNRS, LPCT, UMR 7019, F-54000 Nancy, France
| | - Javier Cerezo
- Departamento de Química and Institute for Advanced Research in Chemical Sciences (IAdChem), Universidad Autónoma de Madrid, 28049 Madrid, Spain
| | - Giacomo Prampolini
- Istituto di Chimica dei Composti Organo Metallici, Consiglio Nazionale delle Ricerche, (ICCOM-CNR) SS di Pisa, Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa, Italy
| | - Fabrizio Santoro
- Istituto di Chimica dei Composti Organo Metallici, Consiglio Nazionale delle Ricerche, (ICCOM-CNR) SS di Pisa, Area della Ricerca, via G. Moruzzi 1, I-56124 Pisa, Italy
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10
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Mancini G, Del Galdo S, Chandramouli B, Pagliai M, Barone V. Computational Spectroscopy in Solution by Integration of Variational and Perturbative Approaches on Top of Clusterized Molecular Dynamics. J Chem Theory Comput 2020; 16:5747-5761. [PMID: 32697580 PMCID: PMC8009517 DOI: 10.1021/acs.jctc.0c00454] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
![]()
Multiscale QM/MM approaches have
become the most suitable and effective
methods for the investigation of spectroscopic properties of medium-
or large-size chromophores in condensed phases. On these grounds,
we are developing a novel workflow aimed at improving the generality,
reliability, and ease of use of the available tools. In the present
paper, we report the latest developments of such an approach with
specific reference to a general workplan starting with the addition
of acetonitrile to the panel of solvents already available in the
General Liquid Optimized Boundary (GLOB) model enforcing nonperiodic
boundary conditions (NPBC). Next, the solvatochromic shifts induced
by acetonitrile on both rigid (uracil and thymine) and flexible (thyrosine)
chromophores have been studied introducing in our software a number
of new features ranging from rigid-geometry NPBC molecular dynamics
based on the quaternion formalism to a full integration of variational
(ONIOM) and perturbative (perturbed matrix method (PMM)) approaches
for describing different solute–solvent topologies and local
fluctuations, respectively. Finally, thymine and uracil have been
studied also in methanol to point out the generality of the computational
strategy. While further developments are surely needed, the strengths
of our integrated approach even in its present version are demonstrated
by the accuracy of the results obtained by an unsupervised approach
and coupled to a computational cost strongly reduced with respect
to that of conventional QM/MM models without any appreciable accuracy
deterioration.
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Affiliation(s)
- Giordano Mancini
- Scuola Normale Superiore di Pisa, Piazza dei Cavalieri 7, I-56126 Pisa, Italy.,Istituto Nazionale di Fisica Nucleare (INFN) sezione di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
| | - Sara Del Galdo
- Scuola Normale Superiore di Pisa, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
| | | | - Marco Pagliai
- Dipartimento di Chimica "Ugo Schiff", Università degli Studi di Firenze, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore di Pisa, Piazza dei Cavalieri 7, I-56126 Pisa, Italy.,Istituto Nazionale di Fisica Nucleare (INFN) sezione di Pisa, Largo Bruno Pontecorvo 3, 56127 Pisa, Italy
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11
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Del Galdo S, Fusè M, Barone V. CPL Spectra of Camphor Derivatives in Solution by an Integrated QM/MD Approach. Front Chem 2020; 8:584. [PMID: 32733856 PMCID: PMC7358700 DOI: 10.3389/fchem.2020.00584] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 06/05/2020] [Indexed: 11/16/2022] Open
Abstract
We extend a recently proposed computational strategy for the simulation of absorption spectra of semi-rigid molecular systems in condensed phases to the emission spectra of flexible chromophores. As a case study, we have chosen the CPL spectrum of camphor in methanol solution, which shows a well-defined bisignate shape. The first step of our approach is the quantum mechanical computation of reference spectra including vibrational averaging effects and taking bulk solvent effects into account by means of the polarizable continuum model. In the present case, the large amplitude inversion mode is explicitly treated by a numerical approach, whereas the other small-amplitude vibrational modes are taken into account within the harmonic approximation. Next, the snapshots of classical molecular dynamics computations are clusterized and one representative configuration from each cluster is used to compute a reference spectrum. In the present case, different clusters correspond to the two stable conformers of camphor in the S1 excited electronic state and, for each of them, to different numbers of strong solute-solvent hydrogen bonds. Finally, local fluctuation effects within each cluster are taken into account by means of the perturbed matrix model. The overall procedure leads to good agreement with experiment for absorption and emission spectra together with their chiral counterparts, thus allowing to analyze the role of different effects (stereo-electronic, vibrational, environmental) in tuning the overall experimental spectra.
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Affiliation(s)
| | - Marco Fusè
- SMART Laboratory, Scuola Normale Superiore, Pisa, Italy
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12
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Puzzarini C, Spada L, Alessandrini S, Barone V. The challenge of non-covalent interactions: theory meets experiment for reconciling accuracy and interpretation. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2020; 32:343002. [PMID: 32203942 DOI: 10.1088/1361-648x/ab8253] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 03/23/2020] [Indexed: 06/10/2023]
Abstract
In the past decade, many gas-phase spectroscopic investigations have focused on the understanding of the nature of weak interactions in model systems. Despite the fact that non-covalent interactions play a key role in several biological and technological processes, their characterization and interpretation are still far from being satisfactory. In this connection, integrated experimental and computational investigations can play an invaluable role. Indeed, a number of different issues relevant to unraveling the properties of bulk or solvated systems can be addressed from experimental investigations on molecular complexes. Focusing on the interaction of biological model systems with solvent molecules (e.g., water), since the hydration of the biomolecules controls their structure and mechanism of action, the study of the molecular properties of hydrated systems containing a limited number of water molecules (microsolvation) is the basis for understanding the solvation process and how structure and reactivity vary from gas phase to solution. Although hydrogen bonding is probably the most widespread interaction in nature, other emerging classes, such as halogen, chalcogen and pnicogen interactions, have attracted much attention because of the role they play in different fields. Their understanding requires, first of all, the characterization of the directionality, strength, and nature of such interactions as well as a comprehensive analysis of their competition with other non-covalent bonds. In this review, it is shown how state-of-the-art quantum-chemical computations combined with rotational spectroscopy allow for fully characterizing intermolecular interactions taking place in molecular complexes from both structural and energetic points of view. The transition from bi-molecular complex to microsolvation and then to condensed phase is shortly addressed.
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Affiliation(s)
- Cristina Puzzarini
- Dipartimento di Chimica 'Giacomo Ciamician', Via F. Selmi 2, I-40126 Bologna, Italy
| | - Lorenzo Spada
- Dipartimento di Chimica 'Giacomo Ciamician', Via F. Selmi 2, I-40126 Bologna, Italy
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
| | - Silvia Alessandrini
- Dipartimento di Chimica 'Giacomo Ciamician', Via F. Selmi 2, I-40126 Bologna, Italy
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
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13
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Del Galdo S, Fusè M, Barone V. The ONIOM/PMM Model for Effective Yet Accurate Simulation of Optical and Chiroptical Spectra in Solution: Camphorquinone in Methanol as a Case Study. J Chem Theory Comput 2020; 16:3294-3306. [PMID: 32250614 PMCID: PMC7222099 DOI: 10.1021/acs.jctc.0c00124] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
![]()
This paper deals
with the development and first validation of a
composite approach for the simulation of chiroptical spectra in solution
aimed to strongly reduce the number of full QM computations without
any significant accuracy loss. The approach starts from the quantum
mechanical computation of reference spectra including vibrational
averaging effects and taking average solvent effects into account
by means of the polarizable continuum model. Next, the snapshots of
classical molecular dynamics computations are clusterized and one
reference configuration from each cluster is used to compute a reference
spectrum. Local fluctuation effects within each cluster are then taken
into account by means of the perturbed matrix model. The performance
of the proposed approach is tested on the challenging case of the
optical and chiroptical spectra
of camphorquinone in methanol solution. Although further validations
are surely needed, the results of this first study are quite promising
also taking into account that agreement with experimental data is
reached by just a couple of full quantum mechanical geometry optimizations
and frequency computations.
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Affiliation(s)
- Sara Del Galdo
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
| | - Marco Fusè
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
| | - Vincenzo Barone
- Scuola Normale Superiore, Piazza dei Cavalieri 7, I-56126 Pisa, Italy
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14
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Cerezo J, Aranda D, Avila Ferrer FJ, Prampolini G, Santoro F. Adiabatic-Molecular Dynamics Generalized Vertical Hessian Approach: A Mixed Quantum Classical Method To Compute Electronic Spectra of Flexible Molecules in the Condensed Phase. J Chem Theory Comput 2020; 16:1215-1231. [PMID: 31855424 DOI: 10.1021/acs.jctc.9b01009] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
We present a general mixed quantum classical method that couples classical molecular dynamics (MD) and vibronic models to compute the shape of electronic spectra of flexible molecules in the condensed phase without, in principle, any phenomenological broadening. It is based on a partition of the nuclear motions of the solute + solvent system in "soft" and "stiff" vibrational modes and an adiabatic hypothesis that assumes that stiff modes are much faster than soft ones. In this framework, the spectrum is rigorously expressed as a conformational integral of quantum vibronic spectra along the stiff coordinates only. Soft modes enter at the classical level through the conformational distribution that is sampled with classical MD runs. In each configuration, reduced-dimensionality quadratic Hamiltonians are built in the space of the stiff coordinates only, thanks to a generalization of the Vertical Hessian harmonic model and an iterative application of projectors in internal coordinates to remove soft modes. Quantum vibronic spectra, specific for each sampled configuration of the soft coordinates, are then computed at the desired temperature with efficient time-dependent techniques, and the global spectrum simply arises from their average. For consistency of the whole procedure, classical MD runs are performed with quantum-mechanically derived force fields, parameterized at the same level of theory selected for generating the quadratic Hamiltonians along the stiff coordinates. Application to N-methyl-6-oxyquinolinium betaine in water, dithiophene in ethanol, and cyanidine in water is presented to show the performance of the method.
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Affiliation(s)
| | - Daniel Aranda
- CNR-Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), SS di Pisa , Area della Ricerca, via G. Moruzzi 1 , I-56124 Pisa , Italy.,Departamento de Química Física, Facultad de Ciencias, Andalucía Tech , Universidad de Málaga , E-29071 Málaga , Spain
| | - Francisco José Avila Ferrer
- Departamento de Química Física, Facultad de Ciencias, Andalucía Tech , Universidad de Málaga , E-29071 Málaga , Spain
| | - Giacomo Prampolini
- CNR-Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), SS di Pisa , Area della Ricerca, via G. Moruzzi 1 , I-56124 Pisa , Italy
| | - Fabrizio Santoro
- CNR-Consiglio Nazionale delle Ricerche, Istituto di Chimica dei Composti Organo Metallici (ICCOM-CNR), SS di Pisa , Area della Ricerca, via G. Moruzzi 1 , I-56124 Pisa , Italy
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