Lung Wa Chung,† W. M. C. Sameera,‡ Romain Ramozzi,‡ Alister J. Page, Miho Hatanaka,‡ Galina P. Petrova, Travis V. Harris,‡,⊥ Xin Li, Zhuofeng Ke, Fengyi Liu, Hai-Bei Li, Lina Ding, and Keiji Morokuma*,‡ †Department of Chemistry, South University of Science and Technology of China, Shenzhen 518055, China ‡Fukui Institute for Fundamental Chemistry, Kyoto University, 34-4 Takano Nishihiraki-cho, Sakyo, Kyoto 606-8103, Japan Newcastle Institute for Energy and Resources, The University of Newcastle, Callaghan 2308, Australia Faculty of Chemistry and Pharmacy, University of Sofia, Bulgaria Boulevard James Bourchier 1, 1164 Sofia, Bulgaria Department of Chemistry, State University of New York at Oswego, Oswego, New York 13126, United States State Key Laboratory of Molecular Reaction Dynamics, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China School of Chemistry and Chemical Engineering, Sun Yat-sen University, Guangzhou 510275, China Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry and Chemical Engineering, Shaanxi Normal University, Xi’an, Shaanxi 710119, China School of Ocean, Shandong University, Weihai 264209, China School of Pharmaceutical Sciences, Zhengzhou University, 100 Kexue Avenue, Zhengzhou, Henan 450001, China

The ONIOM Method and Its Applications

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange-correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear-electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an "open teamware" model and an increasingly modular design.

Software for the frontiers of quantum chemistry: An overview of developments in the Q-Chem 5 package

The photophysics and photochemistry of DNA is of great importance due to the potential damage of the genetic code by UV light. Quantum mechanical studies have played a key role in interpretating the results of modern time-resolved pump-probe spectroscopy, and in elucidating the main photoactivated reactive paths. This review provides a concise, complete picture of the computational studies carried out, approximately, in the past decade. We start with an overview of the photophysics of the nucleobases in the gas phase and in solution. We discuss the proposed mechanisms for ultrafast decay to the ground state, that involve conical intersections, consider the role of triplet states, and analyze how the solvent modulates the photophysics. Then we move to larger systems, from dinucleotides to single- and double-stranded oligonucleotides. We focus on the possible role of charge transfer and delocalized or excitonic states in the photophysics of these systems and discuss the main photochemical paths. We finish with an outlook on the current challenges in the field and future directions of research.

Quantum Mechanical Studies on the Photophysics and the Photochemistry of Nucleic Acids and Nucleobases

Interest in molecular crystals has grown thanks to their relevance to pharmaceuticals, organic semiconductor materials, foods, and many other applications. Electronic structure methods have become an increasingly important tool for modeling molecular crystals and polymorphism. This article reviews electronic structure techniques used to model molecular crystals, including periodic density functional theory, periodic second-order Moller-Plesset perturbation theory, fragment-based electronic structure methods, and diffusion Monte Carlo. It also discusses the use of these models for predicting a variety of crystal properties that are relevant to the study of polymorphism, including lattice energies, structures, crystal structure prediction, polymorphism, phase diagrams, vibrational spectroscopies, and nuclear magnetic resonance spectroscopy. Finally, tools for analyzing crystal structures and intermolecular interactions are briefly discussed.

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Modeling Polymorphic Molecular Crystals with Electronic Structure Theory

Understanding the properties of electronically excited states is a challenging task that becomes increasingly important for numerous applications in chemistry, molecular physics, molecular biology, and materials science. A substantial impact is exerted by the fascinating progress in time-resolved spectroscopy, which leads to a strongly growing demand for theoretical methods to describe the characteristic features of excited states accurately. Whereas for electronic ground state problems of stable molecules the quantum chemical methodology is now so well developed that informed nonexperts can use it efficiently, the situation is entirely different concerning the investigation of excited states. This review is devoted to a specific class of approaches, usually denoted as multireference (MR) methods, the generality of which is needed for solving many spectroscopic or photodynamical problems. However, the understanding and proper application of these MR methods is often found to be difficult due to their comp...

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Multireference Approaches for Excited States of Molecules.

The photoinduced Zimmerman di-π-methane (DPM) rearrangement of polycyclic molecules to form synthetically useful cyclopropane derivatives was found experimentally to proceed in a triplet excited state. We have applied state-of-the-art quantum mechanical methods, including M06-2X, DLPNO-CCSD(T) and variational transition-state theory with multidimensional tunneling corrections, to an investigation of the reaction rates of the two steps in the triplet DPM rearrangement of dibenzobarrelene, benzobarrelene and barrelene. This study predicts a high probability of carbon tunneling in regions around the two consecutive transition states at 200–300 K, and an enhancement in the rates by 104–276/35–67% with carbon tunneling at 200/300 K. The Arrhenius plots of the rate constants were found to be curved at low temperatures. Moreover, the computed 12C/13C kinetic isotope effects were affected significantly by carbon tunneling and temperature. Our predictions of electronically excited-state carbon tunneling and two co...

Computational Prediction of Excited-State Carbon Tunneling in the Two Steps of Triplet Zimmerman Di-π-Methane Rearrangement

By the irradiation of ultraviolet-B (UV-B) light, UVR8 photoreceptor can undergo dissociation of the protein homodimer and regulate gene expression in plants. We have carried out high-level quantum mechanics (QM) and ONIOM(QM:MM) calculations and molecular dynamics (MD) simulations to study spectra of key tryptophan residues in UVR8 homodimer and to clarify the key role of important charged residues and their salt bridges as well as the feasible dissociation mechanism. First, benchmark calculations on the absorption and emission of 3-methylindole in the gas phase have been performed by different QM methods (TD-DFT, CASSCF, MS-CASPT2, and SAC-CI). Twenty different DFT functionals, including double hybrid and Minnesota functionals, were tested, but all these functionals failed to give satisfactory description of two key transitions. In comparison, SAC-CI and CASPT2 methods can give reliable transition energies and a correct order of (1)La and (1)Lb excited states. Furthermore, the vertical absorption and emission energies of tryptophan in UVR8 have been investigated by the ONIOM method. The present results suggest that W285 is the major chromophore of UVR8, while W233 can also sense the UV-B light and may be responsible for exciton coupling. Geometrical effects as well as electrostatic and polarization interactions with the protein matrix were found to influence optical properties of these tryptophan residues in UVR8. At the homodimeric interface, R286-D107 and R338-D44 salt bridges are suggested to play a crucial role for the UVR8 monomerization. In addition, the UV-B induced dissociation mechanism of the UVR8 homodimer has been proposed. The electrostatic repulsion between the partially negatively charged benzene ring of W285 in the (1)La excited state and the negatively charged D44/D107, along with electron and/or proton transfers among W285, R286 (or R338), W233 and D129, was suggested to result in the breakage of the key salt bridges, and destabilization as well as dissociation of the UVR8 dimer. The proposed mechanism also accounts for the fluorescence quenching in UVR8, and the stability and the enhanced red-shifted fluorescence in the W285F mutant.

Theoretical Study on the UVR8 Photoreceptor: Sensing Ultraviolet-B by Tryptophan and Dissociation of Homodimer.

Fluorescent RNA aptamer Spinach can bind and activate a green fluorescent protein (GFP)-like chromophore (an anionic DFHBDI chromophore) displaying green fluorescence. Spectroscopic properties, spectral tuning, and the photoisomerization mechanism in the Spinach-DFHBDI complex have been investigated by high-level QM and hybrid ONIOM(QM:AMBER) methods (QM method: (TD)DFT, SF-BHHLYP, SAC-CI, LT-DF-LCC2, CASSCF, or MS-CASPT2), as well as classical molecular dynamics (MD) simulations. First, our benchmark calculations have shown that TD-DFT and spin-flip (SF) TD-DFT (SF-BHHLYP) failed to give a satisfactory description of absorption and emission of the anionic DFHBDI chromophore. Comparatively, SAC-CI, LT-DF-LCC2, and MS-CASPT2 can give more reliable transition energies and are mainly used to further study the spectra of the anionic DFHBDI chromophore in Spinach. The RNA environmental effects on the spectral tuning and the photoisomerization mechanism have been elucidated. Our simulations show that interactio...

Xin Li

Papers

The ONIOM Method and Its Applications

Computational Prediction of Excited-State Carbon Tunneling in the Two Steps of Triplet Zimmerman Di-π-Methane Rearrangement

Theoretical Study on the UVR8 Photoreceptor: Sensing Ultraviolet-B by Tryptophan and Dissociation of Homodimer.

Multiscale Simulations on Spectral Tuning and the Photoisomerization Mechanism in Fluorescent RNA Spinach.