1
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Mukhopadhyaya A, Ali ME. Can Iron-Porphyrins Behave as Single-Molecule Magnets? J Phys Chem A 2024. [PMID: 38504619 DOI: 10.1021/acs.jpca.4c00430] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/21/2024]
Abstract
The study of magnetic properties, especially the magnetic anisotropy of iron-porphyrin complexes employing multiconfigurational methods, is quite challenging due to many strongly correlated electrons in nearly degenerate orbitals. However, a prerequisite for observing the magnetic anisotropy and slow magnetization relaxation, the zero-field splitting parameter, D, was experimentally observed decades ago for halide-based axially ligated penta-coordinate Fe(III)-porphyrins. In these complexes, the signs of D were reported mostly as positive; in a few cases, inconclusive signs of the D parameter were also mentioned. However, no ab initio calculations have been reported to shed light on this. Deciphering the electronic structure of these penta-coordinated complexes employing the complete active space self-consistent field method and N-electron valence second-order perturbation theory, we confirm the positive D values. However, a negative D value is highly desired to observe the single-molecule magnet properties without an external magnetic field, which we observed in the Fe(II)-porphyrin complexes with axial imidazole ligands instead of halide ligands. The detailed analysis of the multireference wave functions unravels the role of axial ligands in determining the sign and magnitude of the D parameters.
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Affiliation(s)
| | - Md Ehesan Ali
- Institute of Nano Science and Technology, Mohali, Punjab 140306, India
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2
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Ghosh A, Conradie J. Theoretical Photoelectron Spectroscopy of Quadruple-Bonded Dimolybdenum(II,II) and Ditungsten(II,II) Paddlewheel Complexes: Performance of Common Density Functional Theory Methods. ACS OMEGA 2024; 9:12237-12241. [PMID: 38496970 PMCID: PMC10938323 DOI: 10.1021/acsomega.4c00269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2024] [Revised: 02/13/2024] [Accepted: 02/22/2024] [Indexed: 03/19/2024]
Abstract
We have revisited the gas-phase photoelectron spectra of quadruple-bonded dimolybdenum(II,II) and ditungsten(II,II) paddlewheel complexes with modern density functional theory methods and obtained valuable calibration of four well-known exchange-correlation functionals, namely, BP86, OLYP, B3LYP*, and B3LYP. All four functionals were found to perform comparably, with discrepancies between calculated and experimental ionization potentials ranging from <0.1 to ∼0.5 eV, with the lowest errors observed for the classic pure functional BP86. All four functionals were found to reproduce differences in ionization potentials (IPs) between analogous Mo2 and W2 complexes, as well as large, experimentally observed ligand field effects on the IPs, with near-quantitative accuracy. The calculations help us interpret a number of differences between analogous Mo2 and W2 complexes through the lens of relativistic effects. Thus, relativity results in not only significantly lower IPs for the W2 complexes but also smaller HOMO-LUMO gaps and different triplet states relative to their Mo2 counterparts.
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Affiliation(s)
- Abhik Ghosh
- Department
of Chemistry, UiT − the Arctic University
of Norway, N-9037 Tromsø, Norway
| | - Jeanet Conradie
- Department
of Chemistry, UiT − the Arctic University
of Norway, N-9037 Tromsø, Norway
- Department
of Chemistry, University of the Free State, P.O. Box 339, Bloemfontein 9300, Republic
of South Africa
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3
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de Moraes MMF, Aoto YA. Multi- d-Occupancy as an Alternative Definition for the Double d-Shell Effect. J Phys Chem A 2023; 127:10075-10090. [PMID: 37983730 DOI: 10.1021/acs.jpca.3c04709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Despite the prevalence of first-row transition metal-containing compounds in virtually all areas of chemistry, the accurate modeling of these systems is a known challenge for the theoretical chemistry community. Such a challenge is shown in a myriad of facets; among them are difficulties in defining ground-state multiplicities, disagreement in the results from methods considered highly accurate, and convergence problems in calculations for excited states. These problems cause a scarcity of reliable theoretical data for transition metal-containing systems. In this work, we explore the double d-shell effect that plagues and makes the application of multireference methods to this type of system difficult. We propose an alternative definition for this effect based on the mixing among d-occupancy configurations or the multi-d-occupancy character of the wave function. Moreover, we present a protocol able to include this effect in multireference calculations using an active space smaller than that usually used in the literature. A molybdenum-copper model system and its copper subsystem are used as example study cases, in particular, the molybdenum-copper charge transfer of the former and the electron affinity of the latter. We have shown that our alternative definition can be used to analyze their reference wave functions qualitatively. Based on this qualitative description, it is possible to optimize an active space without a second d-shell able to obtain relative energies accurately. Seeing the double d-shell effect through the lens of a multi-d-occupancy character, it is possible to correctly describe the wave function, improve the accuracy of the relative energies, and reduce the computational cost of multireference calculations. That way, we believe that this alternative definition has the potential to improve the modeling of first-row transition metal-containing compounds both for their ground and excited electronic structures.
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Affiliation(s)
- Matheus Morato F de Moraes
- Center of Mathematics Computing and Cognition, Federal University of ABC (UFABC), Santo André, SP 09280-560, Brazil
| | - Yuri Alexandre Aoto
- Center of Mathematics Computing and Cognition, Federal University of ABC (UFABC), Santo André, SP 09280-560, Brazil
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4
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Ugandi M, Roemelt M. A configuration-based heatbath-CI for spin-adapted multireference electronic structure calculations with large active spaces. J Comput Chem 2023; 44:2374-2390. [PMID: 37589287 DOI: 10.1002/jcc.27203] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 07/24/2023] [Accepted: 07/27/2023] [Indexed: 08/18/2023]
Abstract
This work reports on a spin-pure configuration-based implementation of the heatbath configuration interaction (HCI) algorithm for selective configuration interaction. Besides the obvious advantage of being spin-pure, the presented method combines the compactness of the configurational ansatz with the known efficiency of the HCI algorithm and a variety of algorithmic and conceptual ideas to achieve a high level of performance. In particular, through pruning of the selected configurational space after HCI selection by means of a more strict criterion, a more compact wavefunction representation is obtained. Moreover, the underlying logic of the method allows us to minimize the number of redundant matrix-matrix multiplications while making use of just-in-time compilation to achieve fast diagonalization of the Hamiltonian. The critical search for 2-electron connections within the configurational space is facilitated by a tree-based representation thereof as suggested previously by Gopal et al. Usage of a prefix-based parallelization and batching during the calculation of the PT2-correction leads to a good load balancing and significantly reduced memory requirements for these critical steps of the calculation. In this way, the need for a semistochastic approach to the PT2 correction is avoided even for large configurational spaces. Finally, several test-cases are discussed to demonstrate the strengths and weaknesses of the presented method.
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Affiliation(s)
- Mihkel Ugandi
- Institut für Chemie, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Michael Roemelt
- Institut für Chemie, Humboldt-Universität zu Berlin, Berlin, Germany
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5
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Phung QM, Nam HN, Ghosh A. Local Oxidation States in {FeNO} 6-8 Porphyrins: Insights from DMRG/CASSCF-CASPT2 Calculations. Inorg Chem 2023. [PMID: 38010736 DOI: 10.1021/acs.inorgchem.3c03689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2023]
Abstract
A first DMRG/CASSCF-CASPT2 study of a series of paradigmatic {FeNO}6, {FeNO}7, and {FeNO}8 heme-nitrosyl complexes has led to substantial new insight as well as uncovered key shortcomings of the DFT approach. By virtue of its balanced treatment of static and dynamic correlation, the calculations have provided some of the most authoritative information available to date on the energetics of low- versus high-spin states of different classes of heme-nitrosyl complexes. Thus, the calculations indicate low doublet-quartet gaps of 1-4 kcal/mol for {FeNO}7 complexes and high singlet-triplet gaps of ≳20 kcal/mol for both {FeNO}6 and {FeNO}8 complexes. In contrast, DFT calculations yield widely divergent spin state gaps as a function of the exchange-correlation functional. DMRG-CASSCF calculations also help calibrate DFT spin densities for {FeNO}7 complexes, pointing to those obtained from classic pure functionals as the most accurate. The general picture appears to be that nearly all the spin density of Fe[P](NO) is localized on the Fe, while the axial ligand imidazole (ImH) in Fe[P](NO)(ImH) pushes a part of the spin density onto the NO moiety. An analysis of the DMRG-CASSCF wave function in terms of localized orbitals and of the resulting configuration state functions in terms of resonance forms with varying NO(π*) occupancies has allowed us to address the longstanding question of local oxidation states in heme-nitrosyl complexes. The analysis indicates NO(neutral) resonance forms [i.e., Fe(II)-NO0 and Fe(III)-NO0] as the major contributors to both {FeNO}6 and {FeNO}7 complexes. This finding is at variance with the common formulation of {FeNO}6 hemes as Fe(II)-NO+ species but is consonant with an Fe L-edge XAS analysis by Solomon and co-workers. For the {FeNO}8 complex {Fe[P](NO)}-, our analysis suggests a resonance hybrid description: Fe(I)-NO0 ↔ Fe(II)-NO-, in agreement with earlier DFT studies. Vibrational analyses of the compounds studied indicate an imperfect but fair correlation between the NO stretching frequency and NO(π*) occupancy, highlighting the usefulness of vibrational data as a preliminary indicator of the NO oxidation state.
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Affiliation(s)
- Quan Manh Phung
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
| | - Ho Ngoc Nam
- Institute of Materials Innovation, Institutes of Innovation for Future Society, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
- Department of Chemical Systems Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8603, Japan
| | - Abhik Ghosh
- Department of Chemistry, UiT the Arctic University of Norway, N-9037 Tromsø, Norway
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6
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Radoń M. Benchmarks for transition metal spin-state energetics: why and how to employ experimental reference data? Phys Chem Chem Phys 2023; 25:30800-30820. [PMID: 37938035 DOI: 10.1039/d3cp03537a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2023]
Abstract
Accurate prediction of energy differences between alternative spin states of transition metal complexes is essential in computational (bio)inorganic chemistry-for example, in characterization of spin crossover materials and in the theoretical modeling of open-shell reaction mechanisms-but it remains one of the most compelling problems for quantum chemistry methods. A part of this challenge is to obtain reliable reference data for benchmark studies, as even the highest-level applicable methods are known to give divergent results. This Perspective discusses two possible approaches to method benchmarking for spin-state energetics: using either theoretically computed or experiment-derived reference data. With the focus on the latter approach, an extensive general review is provided for the available experimental data of spin-state energetics and their interpretations in the context of benchmark studies, targeting the possibility of back-correcting the vibrational effects and the influence of solvents or crystalline environments. With a growing amount of experience, these effects can be now not only qualitatively understood, but also quantitatively modeled, providing the way to derive nearly chemically accurate estimates of the electronic spin-state gaps to be used as benchmarks and advancing our understanding of the phenomena related to spin states in condensed phases.
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Affiliation(s)
- Mariusz Radoń
- Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387 Krakow, Krakow, Poland.
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7
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Dey M, Ghosh D. Machine Learning the Quantum Mechanical Wave Function. J Phys Chem A 2023; 127:9159-9166. [PMID: 37906959 DOI: 10.1021/acs.jpca.3c05322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Strongly correlated systems have been challenging to computational chemists for a long time. To solve these systems, multireference methods have been developed over the years. Recently, with the fast development of machine learning and artificial intelligence methods, these methods have also influenced the quest for optimal wave function ansatz. Machine learning approaches have been used in many different flavors. From this perspective, we will discuss the different milestones achieved in the use of machine learning for solving the quantum many body problem.
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Affiliation(s)
- Mandira Dey
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Debashree Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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8
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Kim SY, Park JW. Approximate Excited-State Geometry Optimization with the State-Averaged Adaptive Sampling Configuration Interaction Algorithm with Large Active Spaces. J Chem Theory Comput 2023; 19:7260-7272. [PMID: 37800852 DOI: 10.1021/acs.jctc.3c00808] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/07/2023]
Abstract
The selected configuration interaction (SCI) wave function is a useful approximation to the full configuration interaction (FCI) one. The adaptive sampling CI (ASCI) method is a deterministic SCI method. By combining ASCI and orbital optimization, the ASCI self-consistent field (ASCI-SCF) method, which is an approximation of the complete active space self-consistent field (CASSCF) method, can be formulated as well. However, their applicability has been tested mainly on the systems in their electronically ground states. In this work, we implement the state-average (SA) ansatz in ASCI-SCF calculations to calculate excited states. We also derive expressions for the approximate analytical gradient and implement them as a computer program. We demonstrate the applicability of the current method for calculating vertical and adiabatic excitation energies and optimizing the molecular geometries of thermally activated delayed fluorescence (TADF) molecules.
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Affiliation(s)
- So Yeon Kim
- Department of Chemistry, Chungbuk National University (CBNU), Cheongju 28644, Korea
| | - Jae Woo Park
- Department of Chemistry, Chungbuk National University (CBNU), Cheongju 28644, Korea
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9
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Ghassemi Tabrizi S. Systematic determination of coupling constants in spin clusters from broken-symmetry mean-field solutions. J Chem Phys 2023; 159:154106. [PMID: 37855312 DOI: 10.1063/5.0172314] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 09/28/2023] [Indexed: 10/20/2023] Open
Abstract
Quantum-chemical calculations aimed at deriving magnetic coupling constants in exchange-coupled spin clusters commonly utilize a broken-symmetry (BS) approach. This involves calculating several distinct collinear spin configurations, predominantly by density-functional theory. The energies of these configurations are interpreted in terms of the Heisenberg model, H̃=∑i
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Affiliation(s)
- Shadan Ghassemi Tabrizi
- Department of Chemistry, University of Potsdam, Karl-Liebknecht-Str. 24-25, D-14476 Potsdam-Golm, Germany
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10
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Phung QM, Nam HN, Saitow M. Unraveling the Spin-State Energetics of FeN 4 Complexes with Ab Initio Methods. J Phys Chem A 2023; 127:7544-7556. [PMID: 37651105 DOI: 10.1021/acs.jpca.3c04254] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/01/2023]
Abstract
A systematic analysis was conducted to explore the spin-state energetics of a series of 19 FeN4 complexes. The performance of a large number of multireference methods was assessed, highlighting the significant challenges associated with accurately describing the spin-state energetics of FeN4 complexes. Most multireference methods were found to be susceptible to errors originating from the reference CASSCF wavefunction, leading to an overstabilization of high-spin states. Nonetheless, a few multireference methods, namely, CASPT2/CC, DSRG-MRPT3, and LDSRG(2), demonstrated promising performance compared to the benchmark CCSD(T) method. Furthermore, our study revealed that FeN4 complexes having a quintet ground state are exceedingly rare. Accordingly, only one specific model (Fe(L2)) and one synthesized complex (Fe(OTBP)) have the quintet ground state among the studied complexes. This scarcity of quintet FeN4 complexes highlights the unique nature of these systems and raises intriguing questions regarding the factors influencing spin states, such as the size of the macrocycle cavity, the introduction of substituents, or the induction of out-of-plane deformation.
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Affiliation(s)
- Quan Manh Phung
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
- Institute of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Ho Ngoc Nam
- Institute of Materials Innovation, Institutes of Innovation for Future Society, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8601, Japan
| | - Masaaki Saitow
- Department of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
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11
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Fitzhugh HC, Furness JW, Pederson MR, Peralta JE, Sun J. Comparative Density Functional Theory Study of Magnetic Exchange Couplings in Dinuclear Transition-Metal Complexes. J Chem Theory Comput 2023; 19:5760-5772. [PMID: 37582098 PMCID: PMC10500985 DOI: 10.1021/acs.jctc.3c00336] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Indexed: 08/17/2023]
Abstract
Multicenter transition-metal complexes (MCTMs) with magnetically interacting ions have been proposed as components for information-processing devices and storage units. For any practical application of MCTMs as magnetic units, it is crucial to characterize their magnetic behavior, and in particular, the isotropic magnetic exchange coupling, J, between its magnetic centers. Due to the large size of typical MCTMs, density functional theory is the only practical electronic structure method for evaluating the J coupling. Here, we assess the accuracy of different density functional approximations for predicting the magnetic couplings of eight dinuclear transition-metal complexes, including five dimanganese, two dicopper, and one divanadium with known reliable experimental J couplings spanning from ferromagnetic to strong antiferromagnetic. The density functionals considered include global hybrid functionals which mix semilocal density functional approximations and exact exchange with a fixed admixing parameter, six local hybrid functionals where the admixing parameters are extended to be spatially dependent, the SCAN and r2SCAN meta-generalized gradient approximations (GGAs), and two widely used GGAs. We found that global hybrids tested in this work have a tendency to over-correct the error in magnetic coupling parameters from the Perdew-Burke-Ernzerhof (PBE) GGA as seen for manganese complexes. The performance of local hybrid density functionals shows no improvement in terms of bias and is scattered without a clear trend, suggesting that more efforts are needed for the extension from global to local hybrid density functionals for this particular property. The SCAN and r2SCAN meta-GGAs are found to perform as well as benchmark global hybrids on most tested complexes. We further analyze the charge density redistribution of meta-GGAs as well as global and local hybrid density functionals with respect to that of PBE, in connection to the self-interaction error or delocalization error.
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Affiliation(s)
- Henry C. Fitzhugh
- Department
of Physics and Engineering Physics, Tulane
University, New Orleans, Louisiana 70118, United States
| | - James W. Furness
- Department
of Physics and Engineering Physics, Tulane
University, New Orleans, Louisiana 70118, United States
| | - Mark R. Pederson
- Department
of Physics, The University of Texas at El
Paso, El Paso, Texas 79968, United States
| | - Juan E. Peralta
- Department
of Physics and Science of Advanced Materials, Central Michigan University, Mount Pleasant, Michigan 48859, United States
| | - Jianwei Sun
- Department
of Physics and Engineering Physics, Tulane
University, New Orleans, Louisiana 70118, United States
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12
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Rastetter U, Jacobi von Wangelin A, Herrmann C. Redox-active ligands as a challenge for electronic structure methods. J Comput Chem 2023; 44:468-479. [PMID: 36326153 DOI: 10.1002/jcc.27013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2022] [Revised: 07/27/2022] [Accepted: 08/19/2022] [Indexed: 11/06/2022]
Abstract
To improve the catalytic activity of 3d transition metal catalysts, redox-active ligands are a promising tool. These ligands influence the oxidation state of the metal center as well as the ground spin-state and make the experimental determination of both properties challenging. Therefore, first-principles calculations, in particular employing density functional theory with a proper choice of exchange-correlation (xc) functional, are crucial. Common xc functionals were tested on a simple class of metal complexes: homoleptic, octahedral tris(diimine) iron(II) complexes. The spin-state energy splittings for most of these complexes showed the expected linear dependence on the amount of exact exchange included in the xc functionals. Even though varying redox-activity affects the electronic structure of the complexes considerably, the sensitivity of the spin-state energetics to the exact exchange admixture is surprisingly small. For iron(II) complexes with highly redox-active ligands and for a broad range of ligands in the reduced tris(diimine) iron(I) complexes, self-consistent field convergence to local minima was observed, which differ from the global minimum in the redox state of the ligand. This may also result in convergence to a molecular structure that corresponds to an energetically higher-lying local minimum. One criterion to detect such behavior is a change in the sign of the slope for the dependence of the spin-state energy splittings on the amount of exact exchange. We discuss possible protocols for dealing with such artifacts in cases in which a large number of calculations makes checking by hand unfeasible.
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Affiliation(s)
- Ursula Rastetter
- Department of Chemistry, University of Hamburg, Hamburg, Germany
| | | | - Carmen Herrmann
- Department of Chemistry, University of Hamburg, Hamburg, Germany
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13
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Roy S, Paul S, Misra A. A Theoretical Account of the Coupling between Metal- and Ligand-centred Spins. Chemphyschem 2023; 24:e202200889. [PMID: 36622254 DOI: 10.1002/cphc.202200889] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2022] [Revised: 01/04/2023] [Accepted: 01/09/2023] [Indexed: 01/10/2023]
Abstract
This study addresses the magnetic interaction between paramagnetic metal ions and the radical ligands taking the [CuII (hfac)2 (imVDZ)] and [MII (hfac)2 (pyDTDA)] (imVDZ=1,5-dimethyl-3-(1-methyl-2-imidazolyl)-6-oxoverdazyl; hfac=(1,1,1,5,5,5)hexafluroacetylacetonate; pyDTDA=4-(2'-pyridyl)-1,2,3,5-dithiadiazolyl), (M=Cu, Ni, Co, Fe, Mn) compounds as reference systems. The coupling between the metal and ligand spins is quantified in terms of the exchange coupling constant (J) in the platform of density functional theory (DFT) and the wave function-based complete active space self-consistent field (CASSCF) method. Application of DFT and broken symmetry (BS) formalism results ferromagnetic coupling for all the transition metal complexes except the Mn(II) complex. This DFT-BS prediction of magnetic nature matches with the experimental finding for all the complexes other than the Fe(II)-pyDTDA complex, for which an antiferromagnetic coupling between high spin iron and the thiazyl ligand has been reported. However, evaluation of spin state energetics through the multiconfigurational wave function-based method produces the S=3/2 ground spin state for the iron-thiazyl in parity with experiment. Electronic structure analyses find the overlap between the metal- and ligand-based singly occupied molecular orbitals (SOMOs) to be one of the major reasons attributing to different extent of exchange coupling in the systems under investigation.
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Affiliation(s)
- Sriparna Roy
- Department of Chemistry, University of North Bengal, Siliguri, Darjeeling , 734013, India
| | - Satadal Paul
- Department of Chemistry, Bangabasi Morning College, 19 R.C Sarani, Kolkata, 700009, India
| | - Anirban Misra
- Department of Chemistry, University of North Bengal, Siliguri, Darjeeling , 734013, India
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14
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Lubitz W, Pantazis DA, Cox N. Water oxidation in oxygenic photosynthesis studied by magnetic resonance techniques. FEBS Lett 2023; 597:6-29. [PMID: 36409002 DOI: 10.1002/1873-3468.14543] [Citation(s) in RCA: 12] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2022] [Revised: 11/14/2022] [Accepted: 11/15/2022] [Indexed: 11/23/2022]
Abstract
The understanding of light-induced biological water oxidation in oxygenic photosynthesis is of great importance both for biology and (bio)technological applications. The chemically difficult multistep reaction takes place at a unique protein-bound tetra-manganese/calcium cluster in photosystem II whose structure has been elucidated by X-ray crystallography (Umena et al. Nature 2011, 473, 55). The cluster moves through several intermediate states in the catalytic cycle. A detailed understanding of these intermediates requires information about the spatial and electronic structure of the Mn4 Ca complex; the latter is only available from spectroscopic techniques. Here, the important role of Electron Paramagnetic Resonance (EPR) and related double resonance techniques (ENDOR, EDNMR), complemented by quantum chemical calculations, is described. This has led to the elucidation of the cluster's redox and protonation states, the valence and spin states of the manganese ions and the interactions between them, and contributed substantially to the understanding of the role of the protein surrounding, as well as the binding and processing of the substrate water molecules, the O-O bond formation and dioxygen release. Based on these data, models for the water oxidation cycle are developed.
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Affiliation(s)
- Wolfgang Lubitz
- Max-Planck-Institut für Chemische Energiekonversion, Mülheim/Ruhr, Germany
| | | | - Nicholas Cox
- Research School of Chemistry, Australian National University, Canberra, ACT, Australia
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15
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Ferrari P, Gómez-Coca S. The spin magnetic order of Co n+ ( n ≤ 5) clusters. Phys Chem Chem Phys 2022; 24:23128-23134. [PMID: 36128751 DOI: 10.1039/d2cp03643f] [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
The magnetism of transition metal clusters has been for decades a complicated puzzle, with experimental results disagreeing with calculations performed within the density functional theory formalism. In this work, we provide a key to this puzzle by investigating the lowest-energy spin states of cobalt cluster, Con+ (n ≤ 5), using CASSCF/NEVPT2 calculations with very large active spaces. The geometries as well as the spin configurations adopted by the clusters in their ground-state are known from experiments, making Con+ clusters an ideal model system for theoretical investigation. Here, using the experimentally known geometries determined by far-infrared spectroscopy as inputs, we calculated the lowest-energy spin configurations of the clusters, revealing that the CASSCF/NEVPT2 formalism correctly predicts the preferred electronic configuration of the clusters known experimentally. This is in contrast to the widely used density functional theory, with results that depend on the selected exchange-correlation functional. The reasons for the failure of density functional theory, in opposition to CASSCF/NEVPT2, are discussed, providing a solid framework for investigating other transition metal and transition metal oxide clusters.
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Affiliation(s)
- Piero Ferrari
- Quantum Solid-State Physics, Department of Physics and Astronomy, KU Leuven, Celestijnenlaan 200d, 3001, Leuven, Belgium. .,Institute for Molecules and Materials, FELIX Laboratory, Radboud University, Toernooiveld 7, 6525 ED, Nijmegen, The Netherlands
| | - Silvia Gómez-Coca
- Departament de Química Inorgànica i Orgànica and Institut de Química Teòrica i Computacional, Universitat de Barcelona, Diagonal 645, 08028, Barcelona, Spain.
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16
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Drosou M, Mitsopoulou CA, Pantazis DA. Reconciling Local Coupled Cluster with Multireference Approaches for Transition Metal Spin-State Energetics. J Chem Theory Comput 2022; 18:3538-3548. [PMID: 35582788 PMCID: PMC9202354 DOI: 10.1021/acs.jctc.2c00265] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
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Spin-state energetics
of transition metal complexes remain one
of the most challenging targets for electronic structure methods.
Among single-reference wave function approaches, local correlation
approximations to coupled cluster theory, most notably the domain-based
local pair natural orbital (DLPNO) approach, hold the promise of bringing
the accuracy of coupled cluster theory with single, double, and perturbative
triple excitations, CCSD(T), to molecular systems of realistic size
with acceptable computational cost. However, recent studies on spin-state
energetics of iron-containing systems raised doubts about the ability
of the DLPNO approach to adequately and systematically approximate
energetics obtained by the reference-quality complete active space
second-order perturbation theory with coupled-cluster semicore correlation,
CASPT2/CC. Here, we revisit this problem using a diverse set of iron
complexes and examine several aspects of the application of the DLPNO
approach. We show that DLPNO-CCSD(T) can accurately reproduce both
CASPT2/CC and canonical CCSD(T) results if two basic principles are
followed. These include the consistent use of the improved iterative
(T1) versus the semicanonical perturbative triple corrections
and, most importantly, a simple two-point extrapolation to the PNO
space limit. The latter practically eliminates errors arising from
the default truncation of electron-pair correlation spaces and should
be viewed as standard practice in applications of the method to transition
metal spin-state energetics. Our results show that reference-quality
results can be readily achieved with DLPNO-CCSD(T) if these principles
are followed. This is important also in view of the applicability
of the method to larger single-reference systems and multinuclear
clusters, whose treatment of dynamic correlation would be challenging
for multireference-based approaches.
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Affiliation(s)
- Maria Drosou
- Inorganic Chemistry Laboratory, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou 15771, Greece
| | - Christiana A Mitsopoulou
- Inorganic Chemistry Laboratory, National and Kapodistrian University of Athens, Panepistimiopolis, Zografou 15771, Greece
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
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17
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Benediktsson B, Bjornsson R. Analysis of the Geometric and Electronic Structure of Spin-Coupled Iron-Sulfur Dimers with Broken-Symmetry DFT: Implications for FeMoco. J Chem Theory Comput 2022; 18:1437-1457. [PMID: 35167749 PMCID: PMC8908755 DOI: 10.1021/acs.jctc.1c00753] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
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The open-shell electronic
structure of iron–sulfur clusters
presents considerable challenges to quantum chemistry, with the complex
iron–molybdenum cofactor (FeMoco) of nitrogenase representing
perhaps the ultimate challenge for either wavefunction or density
functional theory. While broken-symmetry density functional theory
has seen some success in describing the electronic structure of such
cofactors, there is a large exchange–correlation functional
dependence in calculations that is not fully understood. In this work,
we present a geometric benchmarking test set, FeMoD11, of synthetic
spin-coupled Fe–Fe and Mo–Fe dimers, with relevance
to the molecular and electronic structure of the Mo-nitrogenase FeMo
cofactor. The reference data consists of high-resolution crystal structures
of metal dimer compounds in different oxidation states. Multiple density
functionals are tested on their ability to reproduce the local geometry,
specifically the Fe–Fe/Mo–Fe distance, for both antiferromagnetically
coupled and ferromagnetically coupled dimers via the broken-symmetry
approach. The metal–metal distance is revealed not only to
be highly sensitive to the amount of exact exchange in the functional
but also to the specific exchange and correlation functionals. For
the antiferromagnetically coupled dimers, the calculated metal–metal
distance correlates well with the covalency of the bridging metal–ligand
bonds, as revealed via the corresponding orbital analysis, Hirshfeld
S/Fe charges, and Fe–S Mayer bond order. Superexchange via
bridging ligands is expected to be the dominant interaction in these
dimers, and our results suggest that functionals that predict accurate
Fe–Fe and Mo–Fe distances describe the overall metal–ligand
covalency more accurately and in turn the superexchange of these systems.
The best performing density functionals of the 16 tested for the FeMoD11
test set are revealed to be either the nonhybrid functionals r2SCAN and B97-D3 or hybrid functionals with 10–15% exact
exchange: TPSSh and B3LYP*. These same four functionals are furthermore
found to reproduce the high-resolution X-ray structure of FeMoco well
according to quantum mechanics/molecular mechanics (QM/MM) calculations.
Almost all nonhybrid functionals systematically underestimate Fe–Fe
and Mo–Fe distances (with r2SCAN and B97-D3 being
the sole exceptions), while hybrid functionals with >15% exact
exchange
(including range-separated hybrid functionals) overestimate them.
The results overall suggest r2SCAN, B97-D3, TPSSh, and
B3LYP* as accurate density functionals for describing the electronic
structure of iron–sulfur clusters in general, including the
complex FeMoco cluster of nitrogenase.
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Affiliation(s)
- Bardi Benediktsson
- Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik, Iceland
| | - Ragnar Bjornsson
- Science Institute, University of Iceland, Dunhagi 3, 107 Reykjavik, Iceland.,Max-Planck Institute for Chemical Energy Conversion, Stiftstrasse 34-36, 45470 Mülheim an der Ruhr, Germany
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18
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Affiliation(s)
- Milica Feldt
- Leibniz Institute for Catalysis: Leibniz-Institut fur Katalyse eV Theory & Catalysis Albert-Einstein-Str 29A 18059 Rostock GERMANY
| | - Quan Manh Phung
- Nagoya University: Nagoya Daigaku Department of Chemistry JAPAN
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19
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Larsson HR, Zhai H, Gunst K, Chan GKL. Matrix Product States with Large Sites. J Chem Theory Comput 2022; 18:749-762. [DOI: 10.1021/acs.jctc.1c00957] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Henrik R. Larsson
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Huanchen Zhai
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Klaas Gunst
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
- Center for Molecular Modeling, Ghent University, Technologiepark 46, B-9052 Zwijnaarde, Belgium
- Department of Physics and Astronomy, Ghent University, Krijgslaan 281, S9, B-9000 Ghent, Belgium
| | - Garnet Kin-Lic Chan
- Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, California 91125, United States
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20
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Phung QM, Muchammad Y, Yanai T, Ghosh A. A DMRG/CASPT2 Investigation of Metallocorroles: Quantifying Ligand Noninnocence in Archetypal 3d and 4d Element Derivatives. JACS AU 2021; 1:2303-2314. [PMID: 34984418 PMCID: PMC8717376 DOI: 10.1021/jacsau.1c00417] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/22/2021] [Indexed: 05/03/2023]
Abstract
Hybrid density functional theory (B3LYP) and density matrix renormalization group (DMRG) theory have been used to quantitatively compare the degree of ligand noninnocence (corrole radical character) in seven archetypal metallocorroles. The seven complexes, in decreasing order of corrole noninnocent character, are Mn[Cor]Cl > Fe[Cor]Cl > Fe[Cor](NO) > Mo[Cor]Cl2 > Ru[Cor](NO) ≈ Mn[Cor]Ph ≈ Fe[Cor]Ph ≈ 0, where [Cor] refers to the unsubstituted corrolato ligand. DMRG-based second-order perturbation theory calculations have also yielded detailed excited-state energetics data on the compounds, shedding light on periodic trends involving middle transition elements. Thus, whereas the ground state of Fe[Cor](NO) (S = 0) is best described as a locally S = 1/2 {FeNO}7 unit antiferromagnetically coupled to a corrole A' radical, the calculations confirm that Ru[Cor](NO) may be described as simply {RuNO}6-Cor3-, that is, having an innocent corrole macrocycle. Furthermore, whereas the ferromagnetically coupled S = 1{FeNO}7-Cor•2- state of Fe[Cor](NO) is only ∼17.5 kcal/mol higher than the S = 0 ground state, the analogous triplet state of Ru[Cor](NO) is higher by a far larger margin (37.4 kcal/mol) relative to the ground state. In the same vein, Mo[Cor]Cl2 exhibits an adiabatic doublet-quartet gap of 36.1 kcal/mol. The large energy gaps associated with metal-ligand spin coupling in Ru[Cor](NO) and Mo[Cor]Cl2 reflect the much greater covalent character of 4d-π interactions relative to analogous interactions involving 3d orbitals. As far as excited-state energetics is concerned, DMRG-CASPT2 calculations provide moderate validation for hybrid density functional theory (B3LYP) for qualitative purposes, but underscore the possibility of large errors (>10 kcal/mol) in interstate energy differences.
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Affiliation(s)
- Quan Manh Phung
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
- Institute
of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Yasin Muchammad
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Takeshi Yanai
- Department
of Chemistry, Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
- Institute
of Transformative Bio-Molecules (WPI-ITbM), Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602, Japan
| | - Abhik Ghosh
- Department
of Chemistry, UiT-The Arctic University
of Norway, N-9037 Tromsø, Norway
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21
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Jeong W, Gaggioli CA, Gagliardi L. Active Learning Configuration Interaction for Excited-State Calculations of Polycyclic Aromatic Hydrocarbons. J Chem Theory Comput 2021; 17:7518-7530. [PMID: 34787422 PMCID: PMC8675132 DOI: 10.1021/acs.jctc.1c00769] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2021] [Indexed: 11/30/2022]
Abstract
We present the active learning configuration interaction (ALCI) method for multiconfigurational calculations based on large active spaces. ALCI leverages the use of an active learning procedure to find important electronic configurations among the full configurational space generated within an active space. We tested it for the calculation of singlet-singlet excited states of acenes and pyrene using different machine learning algorithms. The ALCI method yields excitation energies within 0.2-0.3 eV from those obtained by traditional complete active-space configuration interaction (CASCI) calculations (affordable for active spaces up to 16 electrons in 16 orbitals) by including only a small fraction of the CASCI configuration space in the calculations. For larger active spaces (we tested up to 26 electrons in 26 orbitals), not affordable with traditional CI methods, ALCI captures the trends of experimental excitation energies. Overall, ALCI provides satisfactory approximations to large active-space wave functions with up to 10 orders of magnitude fewer determinants for the systems presented here. These ALCI wave functions are promising and affordable starting points for the subsequent second-order perturbation theory or pair-density functional theory calculations.
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Affiliation(s)
- WooSeok Jeong
- Department
of Chemistry, Nanoporous Materials Genome Center, Chemical Theory
Center, and Minnesota Supercomputing Institute, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | - Carlo Alberto Gaggioli
- Department
of Chemistry, Pritzker School of Molecular Engineering, James Franck
Institute, Chicago Center for Theoretical Chemistry, University of Chicago, Chicago, Illinois 60637, United States
| | - Laura Gagliardi
- Department
of Chemistry, Pritzker School of Molecular Engineering, James Franck
Institute, Chicago Center for Theoretical Chemistry, University of Chicago, Chicago, Illinois 60637, United States
- Argonne
National Laboratory, Lemont, Illinois 60439, United States
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22
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Maurer LR, Bursch M, Grimme S, Hansen A. Assessing Density Functional Theory for Chemically Relevant Open-Shell Transition Metal Reactions. J Chem Theory Comput 2021; 17:6134-6151. [PMID: 34546754 DOI: 10.1021/acs.jctc.1c00659] [Citation(s) in RCA: 55] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Due to the principle lack of systematic improvement possibilities of density functional theory, careful assessment of the performance of density functional approximations (DFAs) on well-designed benchmark sets, for example, for reaction energies and barrier heights, is crucial. While main-group chemistry is well covered by several available sets, benchmark data for transition metal chemistry is sparse. This is especially the case for larger, chemically relevant molecules. Addressing this issue, we recently introduced the MOR41 benchmark which covers chemically relevant reactions of closed-shell complexes. In this work, we extend these efforts to single-reference open-shell systems and introduce the "reactions of open-shell single-reference transition metal complexes" (ROST61) benchmark set. ROST61 includes accurate coupled-cluster reference values for 61 reaction energies with a mean reaction energy of -42.8 kcal mol-1. Complexes with 13-93 atoms covering 20 d-block elements are included, but due to the restriction to single-reference open-shell systems, important elements such as iron or platinum could not be taken into account, or only to a small extent. We assess the performance of 31 DFAs in combination with three London dispersion (LD) correction schemes. Further, DFT-based composite methods, MP2, and a few semiempirical quantum chemical methods are evaluated. Consistent with the results for the MOR41 closed-shell benchmark, we find that the ordering of DFAs according to Jacob's ladder is preserved and that adding an LD correction is crucial, clearly improving almost all tested methods. The recently introduced r2SCAN-3c composite method stands out with a remarkable mean absolute deviation (MAD) of only 2.9 kcal mol-1, which is surpassed only by hybrid DFAs with low amounts of Fock exchange (e.g., 2.3 kcal mol-1 for TPSS0-D4/def2-QZVPP) and double-hybrid (DH) DFAs but at a significantly higher computational cost. The lowest MAD of only 1.6 kcal mol-1 is obtained with the DH DFA PWPB95-D4 in the def2-QZVPP basis set approaching the estimated accuracy of the reference method. Overall, the ROST61 set adds important reference data to a sparsely sampled but practically relevant area of chemistry. At this point, it provides valuable orientation for the application and development of new DFAs and electronic structure methods in general.
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Affiliation(s)
- Leonard R Maurer
- Mulliken Center for Theoretical Chemistry, Institute for Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
| | - Markus Bursch
- Mulliken Center for Theoretical Chemistry, Institute for Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry, Institute for Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
| | - Andreas Hansen
- Mulliken Center for Theoretical Chemistry, Institute for Physical and Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115 Bonn, Germany
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23
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Singh G, Gamboa S, Orio M, Pantazis DA, Roemelt M. Magnetic exchange coupling in Cu dimers studied with modern multireference methods and broken-symmetry coupled cluster theory. Theor Chem Acc 2021. [DOI: 10.1007/s00214-021-02830-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
AbstractSpin-state energetics of exchange-coupled copper complexes pose a persistent challenge for applied quantum chemistry. Here, we provide a comprehensive comparison of all available theoretical approaches to the problem of exchange coupling in two antiferromagnetically coupled bis-μ-hydroxo Cu(II) dimers. The evaluated methods include multireference methods based on the density matrix renormalization group (DMRG), multireference methods that incorporate dynamic electron correlation either perturbatively, such as the N-electron valence state perturbation theory, or variationally, such as the difference-dedicated configuration interaction. In addition, we contrast the multireference results with those obtained using broken-symmetry approaches that utilize either density functional theory or, as demonstrated here for the first time in such systems, a local implementation of coupled cluster theory. The results show that the spin-state energetics of these copper dimers are dominated by dynamic electron correlation and represent an impossible challenge for multireference methods that rely on brute-force expansion of the active space to recover correlation energy. Therefore, DMRG-based methods even at the limit of their applicability cannot describe quantitatively the antiferromagnetic exchange coupling in these dimers, in contrast to dinuclear complexes of earlier transition metal ions. The convergence of the broken-symmetry coupled cluster approach is studied and shown to be a limiting factor for the practical application of the method. The advantages and disadvantages of all approaches are discussed, and recommendations are made for future developments.
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24
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Bodenstein T, Fink K, Heimermann A, van Wüllen C. Development and application of a complete active space spin‐orbit configuration interaction program designed for molecule magnets. Chemphyschem 2021; 23:e202100648. [PMID: 34505748 PMCID: PMC9298407 DOI: 10.1002/cphc.202100648] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Indexed: 12/02/2022]
Abstract
We present a spin‐orbit configuration interaction program which has been tailored for the description of the magnetic properties of polynuclear metal complexes with partially filled d‐ and f‐shells. The spin‐orbit operators are directly included in the configuration interaction program based on Slater‐determinants. The lowest states are obtained by a Block‐Davidson‐type diagonalisation. The usage of localised active orbitals enables the construction of start vectors from tensor products of single‐center wave functions that already include spin‐orbit interaction. This allows for an analysis of the role and the interplay of the different metal centres. Furthermore, in case of weak coupling of the metal centres these tensor products are already close to the final wave functions ensuring fast convergence. In combination with a two‐layer hybrid parallelisation, this makes the program highly efficient. Based on the spin‐orbit coupled wave functions, magnetic D‐tensors, g‐tensors and temperature‐dependent susceptibilities can be calculated. The applicability and performance of the program is shown exemplarily on a trinuclear transition metal (CoIIVIICoII) complex.
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Affiliation(s)
- Tilmann Bodenstein
- UiO: Universitetet i Oslo Department of Chemistry, Hylleraas Center of Quantum Molecular Sciences NORWAY
| | - Karin Fink
- Karlsruher Institut fur Technologie Institute of Nanotechnology Hermann-von-Helmholtz-Platz 1 76344 Eggenstein-Leopoldshafen GERMANY
| | - Andreas Heimermann
- TU Kaiserslautern: Technische Universitat Kaiserslautern Fachbereich Chemie GERMANY
| | - Christoph van Wüllen
- TU Kaiserslautern: Technische Universitat Kaiserslautern Fachbereich Chemie GERMANY
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25
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Drosou M, Pantazis DA. Redox Isomerism in the S 3 State of the Oxygen-Evolving Complex Resolved by Coupled Cluster Theory. Chemistry 2021; 27:12815-12825. [PMID: 34288176 PMCID: PMC8518824 DOI: 10.1002/chem.202101567] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2021] [Indexed: 01/19/2023]
Abstract
The electronic and geometric structures of the water-oxidizing complex of photosystem II in the steps of the catalytic cycle that precede dioxygen evolution remain hotly debated. Recent structural and spectroscopic investigations support contradictory redox formulations for the active-site Mn4 CaOx cofactor in the final metastable S3 state. These range from the widely accepted MnIV 4 oxo-hydroxo model, which presumes that O-O bond formation occurs in the ultimate transient intermediate (S4 ) of the catalytic cycle, to a MnIII 2 MnIV 2 peroxo model representative of the contrasting "early-onset" O-O bond formation hypothesis. Density functional theory energetics of suggested S3 redox isomers are inconclusive because of extreme functional dependence. Here, we use the power of the domain-based local pair natural orbital approach to coupled cluster theory, DLPNO-CCSD(T), to present the first correlated wave function theory calculations of relative stabilities for distinct redox-isomeric forms of the S3 state. Our results enabled us to evaluate conflicting models for the S3 state of the oxygen-evolving complex (OEC) and to quantify the accuracy of lower-level theoretical approaches. Our assessment of the relevance of distinct redox-isomeric forms for the mechanism of biological water oxidation strongly disfavors the scenario of early-onset O-O formation advanced by literal interpretations of certain crystallographic models. This work serves as a case study in the application of modern coupled cluster implementations to redox isomerism problems in oligonuclear transition metal systems.
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Affiliation(s)
- Maria Drosou
- Inorganic Chemistry LaboratoryNational and Kapodistrian University of AthensPanepistimiopolisZografou15771Greece
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für KohlenforschungKaiser-Wilhelm-Platz 145470Mülheim an derRuhrGermany
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26
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Khedkar A, Roemelt M. Modern multireference methods and their application in transition metal chemistry. Phys Chem Chem Phys 2021; 23:17097-17112. [PMID: 34355719 DOI: 10.1039/d1cp02640b] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Transition metal chemistry is a challenging playground for quantum chemical methods owing to the simultaneous presence of static and dynamic electron correlation effects in many systems. Wavefunction based multireference (MR) methods constitute a physically sound and systematically improvable Ansatz to deal with this complexity but suffer from some conceptual difficulties and high computational costs. The latter problem partially arises from the unfavorable scaling of the Full Configuration Interaction (Full-CI) problem which in the majority of MR methods is solved for a subset of the molecular orbital space, the so-called active space. In the last years multiple methods such as modern variants of selected CI, Full-CI Quantum Monte Carlo (FCIQMC) and the density matrix renormalization group (DMRG) have been developed that solve the Full-CI problem approximately for a fraction of the computational cost required by conventional techniques thereby significantly extending the range of applicability of modern MR methods. This perspective review outlines recent advancements in the field of MR electronic structure methods together with the resulting chances and challenges for theoretical studies in the field of transition metal chemistry. In light of its emerging importance a special focus is put on the selection of adequate active spaces and the concomitant development of numerous selection aides in recent years.
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Affiliation(s)
- Abhishek Khedkar
- Lehrstuhl für theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany.
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27
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Welch BK, Almeida NMS, Wilson AK. Super ccCA (s-ccCA): an approach for accurate transition metal thermochemistry. Mol Phys 2021. [DOI: 10.1080/00268976.2021.1963001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Bradley K. Welch
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Nuno M. S. Almeida
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
| | - Angela K. Wilson
- Department of Chemistry, Michigan State University, East Lansing, MI, USA
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28
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Freitag L, González L. The Role of Triplet States in the Photodissociation of a Platinum Azide Complex by a Density Matrix Renormalization Group Method. J Phys Chem Lett 2021; 12:4876-4881. [PMID: 34006109 PMCID: PMC8165699 DOI: 10.1021/acs.jpclett.1c00829] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2021] [Accepted: 05/13/2021] [Indexed: 06/12/2023]
Abstract
Platinum azide complexes are appealing anticancer photochemotherapy drug candidates because they release cytotoxic azide radicals upon light irradiation. Here we present a density matrix renormalization group self-consistent field (DMRG-SCF) study of the azide photodissociation mechanism of trans,trans,trans-[Pt(N3)2(OH)2(NH3)2], including spin-orbit coupling. We find a complex interplay of singlet and triplet electronic excited states that falls into three different dissociation channels at well-separated energies. These channels can be accessed either via direct excitation into barrierless dissociative states or via intermediate doorway states from which the system undergoes non-radiative internal conversion and intersystem crossing. The high density of states, particularly of spin-mixed states, is key to aid non-radiative population transfer and enhance photodissociation along the lowest electronic excited states.
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29
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Ghosh SK, Rano M, Ghosh D. Configuration interaction trained by neural networks: Application to model polyaromatic hydrocarbons. J Chem Phys 2021; 154:094117. [PMID: 33685176 DOI: 10.1063/5.0040785] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The main bottleneck of a stochastic or deterministic configuration interaction method is determining the relative weights or importance of each determinant or configuration, which requires large scale matrix diagonalization. Therefore, these methods can be improved significantly from a computational standpoint if the relative importance of each configuration in the ground and excited states of molecular/model systems can be learned using machine learning techniques such as artificial neural networks (ANNs). We have used neural networks to train the configuration interaction coefficients obtained from full configuration interaction and Monte Carlo configuration interaction methods and have tested different input descriptors and outputs to find the more efficient training techniques. These ANNs have been used to calculate the ground states of one- and two-dimensional Heisenberg spin chains along with Heisenberg ladder systems, which are good approximations of polyaromatic hydrocarbons. We find excellent efficiency of training and the model this trained was used to calculate the variational ground state energies of the systems.
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Affiliation(s)
- Sumanta K Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Madhumita Rano
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
| | - Debashree Ghosh
- School of Chemical Sciences, Indian Association for the Cultivation of Science, Jadavpur, Kolkata 700032, India
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30
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Orio M, Pantazis DA. Successes, challenges, and opportunities for quantum chemistry in understanding metalloenzymes for solar fuels research. Chem Commun (Camb) 2021; 57:3952-3974. [DOI: 10.1039/d1cc00705j] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Overview of the rich and diverse contributions of quantum chemistry to understanding the structure and function of the biological archetypes for solar fuel research, photosystem II and hydrogenases.
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Affiliation(s)
- Maylis Orio
- Aix-Marseille Université
- CNRS
- iSm2
- Marseille
- France
| | - Dimitrios A. Pantazis
- Max-Planck-Institut für Kohlenforschung
- Kaiser-Wilhelm-Platz 1
- 45470 Mülheim an der Ruhr
- Germany
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31
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Drabik G, Szklarzewicz J, Radoń M. Spin-state energetics of metallocenes: How do best wave function and density functional theory results compare with the experimental data? Phys Chem Chem Phys 2021; 23:151-172. [PMID: 33313617 DOI: 10.1039/d0cp04727a] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
We benchmark the accuracy of quantum-chemical methods, including wave function theory methods [coupled cluster theory at the CCSD(T) level, multiconfigurational perturbation-theory (CASPT2, NEVPT2) and internally contracted multireference configuration interaction (MRCI)] and 30 density functional theory (DFT) approximations, in reproducing the spin-state splittings of metallocenes. The reference values of the electronic energy differences are derived from the experimental spin-crossover enthalpy for manganocene and the spectral data of singlet-triplet transitions for ruthenocene, ferrocene, and cobaltocenium. For ferrocene and cobaltocenium we revise the previous experimental interpretations regarding the lowest triplet energy; our argument is based on the comparison with the lowest singlet excitation energy and herein reported, carefully determined absorption spectrum of ferrocene. When deriving vertical energies from the experimental band maxima, we go beyond the routine vertical energy approximation by introducing vibronic corrections based on simulated vibrational envelopes. The benchmarking result confirms the high accuracy of the CCSD(T) method (in particular, for UCCSD(T) based on Hartree-Fock orbitals we find for our dataset: maximum error 0.12 eV, weighted mean absolute error 0.07 eV, weighted mean signed error 0.01 eV). The high accuracy of the single-reference method is corroborated by the analysis of a multiconfigurational character of the complete active space wave function for the triplet state of ferrocene. On the DFT side, our results confirm the non-universality problem with approximate functionals. The present study is an important step toward establishing an extensive and representative benchmark set of experiment-derived spin-state energetics for transition metal complexes.
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Affiliation(s)
- Gabriela Drabik
- Faculty of Chemistry, Jagiellonian University, ul. Gronostajowa 2, 30-387 Kraków, Poland.
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Stepanovic S, Lai R, Elstner M, Gruden M, Garcia-Fernandez P, Cui Q. Improvement of d-d interactions in density functional tight binding for transition metal ions with a ligand field model: assessment of a DFTB3+ U model on nickel coordination compounds. Phys Chem Chem Phys 2020; 22:27084-27095. [PMID: 33220674 PMCID: PMC7737908 DOI: 10.1039/d0cp04694a] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
To improve the description of interactions among the localized d, f electrons in transition metals, we have introduced a ligand-field motivated contribution into the Density Functional Tight Binding (DFTB) model. Referred to as DFTB3+U, the approach treats the d, f electron repulsions with rotationally invariant orbital-orbital interactions and a Hartree-Fock model; this represents a major conceptual improvement over the original DFTB3 approach, which treats the d, f-shell interactions in a highly averaged fashion without orbital level of description. The DFTB3+U approach is tested using a series of nickel compounds that feature Ni(ii) and Ni(iii) oxidation states. By using parameters developed with the original DFTB3 Hamiltonian and empirical +U parameters (F0/2/4 Slater integrals), we observe that the DFTB3+U model indeed provides substantial improvements over the original DFTB3 model for a number of properties of the nickel compounds, including the population and spin polarization of the d-shell, nature of the frontier orbitals, ligand field splitting and the energy different between low and high spin states at OPBE optimized structures. This proof-of-concept study suggests that with self-consistent parameterization of the electronic and +U parameters, the DFTB3+U model can develop into a promising model that can be used to efficiently study reactive events involving transition metals ion condensed phase systems. The methodology can be integrated with other approximate QM methods as well, such as the extended tight binding (xTB) approach.
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Affiliation(s)
- Stepan Stepanovic
- Institute of Physical Chemistry and Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
- Institute of Chemistry, Technology and Metallurgy, University of Belgrade, Njegoševa 12, 11000, Belgrade, Serbia
| | - Rui Lai
- Departments of Chemistry, Physics, Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States
| | - Marcus Elstner
- Institute of Physical Chemistry and Institute of Biological Interfaces (IBG-2), Karlsruhe Institute of Technology, D-76131 Karlsruhe, Germany
| | - Maja Gruden
- University of Belgrade-Faculty of Chemistry, Studentski trg 12-16, 11001 Belgrade, Serbia
| | - Pablo Garcia-Fernandez
- Departamento de Ciencias de la Tierra y Fısica de la Materia Condensada, Universidad de Cantabria, Cantabria Campus Internacional, Avenida de los Castros s/n, 39005 Santander, Spain
| | - Qiang Cui
- Departments of Chemistry, Physics, Biomedical Engineering, Boston University, 590 Commonwealth Avenue, Boston, MA 02215, United States
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Bahlke MP, Mogos N, Proppe J, Herrmann C. Exchange Spin Coupling from Gaussian Process Regression. J Phys Chem A 2020; 124:8708-8723. [DOI: 10.1021/acs.jpca.0c05983] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
- Marc Philipp Bahlke
- Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Natnael Mogos
- Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Jonny Proppe
- Institute of Physical Chemistry, Georg-August University, Tammannstr. 6, 37077 Göttingen, Germany
| | - Carmen Herrmann
- Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
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Mai S, González L. Molecular Photochemistry: Recent Developments in Theory. Angew Chem Int Ed Engl 2020; 59:16832-16846. [PMID: 32052547 PMCID: PMC7540682 DOI: 10.1002/anie.201916381] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/12/2020] [Indexed: 12/16/2022]
Abstract
Photochemistry is a fascinating branch of chemistry that is concerned with molecules and light. However, the importance of simulating light-induced processes is reflected also in fields as diverse as biology, material science, and medicine. This Minireview highlights recent progress achieved in theoretical chemistry to calculate electronically excited states of molecules and simulate their photoinduced dynamics, with the aim of reaching experimental accuracy. We focus on emergent methods and give selected examples that illustrate the progress in recent years towards predicting complex electronic structures with strong correlation, calculations on large molecules, describing multichromophoric systems, and simulating non-adiabatic molecular dynamics over long time scales, for molecules in the gas phase or in complex biological environments.
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Affiliation(s)
- Sebastian Mai
- Photonics InstituteVienna University of TechnologyGusshausstrasse 27–291040ViennaAustria
| | - Leticia González
- Institute of Theoretical ChemistryFaculty of ChemistryUniversity of ViennaWähringer Strasse 171090ViennaAustria
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Mai S, González L. Molekulare Photochemie: Moderne Entwicklungen in der theoretischen Chemie. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.201916381] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Sebastian Mai
- Institut für Photonik Technische Universität Wien Gußhausstraße 27–29 1040 Wien Österreich
| | - Leticia González
- Institut für theoretische Chemie Fakultät für Chemie Universität Wien Währinger Straße 17 1090 Wien Österreich
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Khedkar A, Roemelt M. An ab initio multireference study of reductive eliminations from organoferrates( iii) in the gas-phase: it is all about the spin state. Phys Chem Chem Phys 2020; 22:17677-17686. [DOI: 10.1039/d0cp02834g] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The reductive elimination reaction from organoferrates(iii) of the composition [FeR3R′]− is studied by state-of-the-art multireference electronic structure calculations.
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Affiliation(s)
- Abhishek Khedkar
- Lehrstuhl für Theoretische Chemie
- Ruhr-Universität Bochum
- D-44780 Bochum
- Germany
| | - Michael Roemelt
- Lehrstuhl für Theoretische Chemie
- Ruhr-Universität Bochum
- D-44780 Bochum
- Germany
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Fumanal M, Corminboeuf C, Smit B, Tavernelli I. Optical absorption properties of metal-organic frameworks: solid state versus molecular perspective. Phys Chem Chem Phys 2020; 22:19512-19521. [PMID: 32839805 DOI: 10.1039/d0cp03899g] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The vast chemical space of metal and ligand combinations in Transition Metal Complexes (TMCs) gives rise to a rich variety of electronic excited states with local and non-local character such as intra-ligand (IL), metal-centered (MC), metal-to-ligand (MLCT) or ligand-to-metal charge-transfer (LMCT) states. Those features are equally found in metal organic frameworks (MOFs), defined as modular materials built from metal-nodes connected through organic-ligands. Because of the electronic and structural complexity of MOFs, the computational description of their excited states is a formidable challenge for which two different approaches have been usually followed: the solid state and the molecular perspective. The first consists in analysing the frontier electronic bands and crystal orbitals of the electronic ground state (GS) in periodic boundary conditions, while the latter points to an accurate computation of the excited states in representative clusters at the molecular level. Herein, we apply both approaches to evaluate the optical absorption properties of three experimentally reported Ti(iv) mononuclear MOFs with in silico metal substitutions with Zn(ii), Cd(ii), Fe(ii), Ru(ii) and Zr(iv) ions, thus covering d10, d6 and d0 electronic configurations of 1st and 2nd row TMCs in MOFs. Our analysis captures the main electronic features attributed to these systems while we discuss the main advantages and drawbacks of both approximations.
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Affiliation(s)
- Maria Fumanal
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, EPFL, CH-1015 Lausanne, Switzerland.
| | - Clémence Corminboeuf
- Laboratory for Computational Molecular Design, Institute of Chemical Sciences and Engineering, EPFL, CH-1015 Lausanne, Switzerland.
| | - Berend Smit
- Laboratory of Molecular Simulation, Institut des Sciences et Ingénierie Chimiques, Valais, EPFL, Rue de l'Industrie 17, CH-1951, Sion, Switzerland
| | - Ivano Tavernelli
- IBM Research Zurich, Säumerstrasse 4, 8803 Rüschlikon, Switzerland
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Neale SE, Pantazis DA, Macgregor SA. Accurate computed spin-state energetics for Co(iii) complexes: implications for modelling homogeneous catalysis. Dalton Trans 2020; 49:6478-6487. [DOI: 10.1039/d0dt00993h] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
DLPNO-CCSD(T) calculations provide accurate spin state energetics for a range of Co(iii) complexes and so represent a promising approach to modelling homogeneous catalysis based on Co(iii) species.
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Affiliation(s)
- Samuel E. Neale
- Institute of Chemical Sciences
- Heriot-Watt University
- Edinburgh
- United Kingdom
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Stein CJ, Pantazis DA, Krewald V. Orbital Entanglement Analysis of Exchange-Coupled Systems. J Phys Chem Lett 2019; 10:6762-6770. [PMID: 31613637 DOI: 10.1021/acs.jpclett.9b02417] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
A new tool for the interpretation of multiconfigurational wave functions representing the spin states of exchange-coupled transition metal complexes is introduced. Based on orbital entanglement measures, herein derived from multiconfigurational density matrix renormalization group calculations, the complexity of the wave function is reduced, thus facilitating a connection with established concepts for the interpretation of magnetically coupled systems. We show that the entanglement of localized orbitals with a small basis set is a good representation of the magnetic coupling topology and that it is sensitive to chemical changes in homologous complexes. Furthermore, we introduce a measure for the magnetic relevance of orbitals in the active subspace and a concept for the quantitative comparison of different chemical species. The approach presented here will be easily applicable to higher nuclearity clusters, providing a direct insight into all states of the Heisenberg spin ladder for systems previously accessible only by single-configurational methods.
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Affiliation(s)
- Christopher J Stein
- Department of Chemistry , University of California , Berkeley , California 94720 , United States
- Chemical Sciences Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States
| | - Dimitrios A Pantazis
- Max-Planck-Institut für Kohlenforschung , Kaiser-Wilhelm-Platz 1 , 45470 Mülheim an der Ruhr , Germany
| | - Vera Krewald
- Technische Universität Darmstadt , Fachbereich Chemie, Theoretische Chemie , Alarich-Weiss-Str. 4 , 64287 Darmstadt , Germany
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Abstract
![]()
Fragment
embedding is one way to circumvent the high computational
scaling of accurate electron correlation methods. The challenge of
applying fragment embedding to molecular systems primarily lies in
the strong entanglement and correlation that prevent accurate fragmentation
across chemical bonds. Recently, Schmidt decomposition has been shown
effective for embedding fragments that are strongly coupled to a bath
in several model systems. In this work, we extend a recently developed
quantum embedding scheme, bootstrap embedding (BE), to molecular systems.
The resulting method utilizes the matching conditions naturally arising
from using overlapping fragments to optimize the embedding. Numerical
simulation suggests that the accuracy of the embedding improves rapidly
with fragment size for small molecules, whereas larger fragments that
include orbitals from different atoms may be needed for larger molecules.
BE scales linearly with system size (apart from an integral transform)
and hence can potentially be useful for large-scale calculations.
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Affiliation(s)
- Hong-Zhou Ye
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Nathan D Ricke
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Henry K Tran
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
| | - Troy Van Voorhis
- Department of Chemistry , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States
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Phung QM, Martín-Fernández C, Harvey JN, Feldt M. Ab Initio Calculations for Spin-Gaps of Non-Heme Iron Complexes. J Chem Theory Comput 2019; 15:4297-4304. [DOI: 10.1021/acs.jctc.9b00370] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Affiliation(s)
- Quan Manh Phung
- Department of Chemistry, KU Leuven, Celestijnenlaan 200f, Box 2404, 3001 Leuven, Belgium
| | | | - Jeremy N. Harvey
- Department of Chemistry, KU Leuven, Celestijnenlaan 200f, Box 2404, 3001 Leuven, Belgium
| | - Milica Feldt
- Department of Chemistry, KU Leuven, Celestijnenlaan 200f, Box 2404, 3001 Leuven, Belgium
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Assessment of Double-Hybrid Density Functional Theory for Magnetic Exchange Coupling in Manganese Complexes. INORGANICS 2019. [DOI: 10.3390/inorganics7050057] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Molecular systems containing magnetically interacting (exchange-coupled) manganese ions are important in catalysis, biomimetic chemistry, and molecular magnetism. The reliable prediction of exchange coupling constants with quantum chemical methods is key for tracing the relationships between structure and magnetic properties in these systems. Density functional theory (DFT) in the broken-symmetry approach has been employed extensively for this purpose and hybrid functionals with moderate levels of Hartree–Fock exchange admixture have often been shown to perform adequately. Double-hybrid density functionals that introduce a second-order perturbational contribution to the Kohn–Sham energy are generally regarded as a superior approach for most molecular properties, but their performance remains unexplored for exchange-coupled manganese systems. An assessment of various double-hybrid functionals for the prediction of exchange coupling constants is presented here using a set of experimentally characterized dinuclear manganese complexes that cover a wide range of exchange coupling situations. Double-hybrid functionals perform more uniformly compared to conventional DFT methods, but they fail to deliver improved accuracy or reliability in the prediction of exchange coupling constants. Reparametrized double-hybrid density functionals (DHDFs) perform no better, and most often worse, than the original B2-PLYP double-hybrid method. All DHDFs are surpassed by the hybrid-meta-generalized gradient approximation (GGA) TPSSh functional. Possible directions for future methodological developments are discussed.
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The S3 State of the Oxygen-Evolving Complex: Overview of Spectroscopy and XFEL Crystallography with a Critical Evaluation of Early-Onset Models for O–O Bond Formation. INORGANICS 2019. [DOI: 10.3390/inorganics7040055] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The catalytic cycle of the oxygen-evolving complex (OEC) of photosystem II (PSII) comprises five intermediate states Si (i = 0–4), from the most reduced S0 state to the most oxidized S4, which spontaneously evolves dioxygen. The precise geometric and electronic structure of the Si states, and hence the mechanism of O–O bond formation in the OEC, remain under investigation, particularly for the final steps of the catalytic cycle. Recent advances in protein crystallography based on X-ray free-electron lasers (XFELs) have produced new structural models for the S3 state, which indicate that two of the oxygen atoms of the inorganic Mn4CaO6 core of the OEC are in very close proximity. This has been interpreted as possible evidence for “early-onset” O–O bond formation in the S3 state, as opposed to the more widely accepted view that the O–O bond is formed in the final state of the cycle, S4. Peroxo or superoxo formation in S3 has received partial support from computational studies. Here, a brief overview is provided of spectroscopic information, recent crystallographic results, and computational models for the S3 state. Emphasis is placed on computational S3 models that involve O–O formation, which are discussed with respect to their agreement with structural information, experimental evidence from various spectroscopic studies, and substrate exchange kinetics. Despite seemingly better agreement with some of the available crystallographic interpretations for the S3 state, models that implicate early-onset O–O bond formation are hard to reconcile with the complete line of experimental evidence, especially with X-ray absorption, X-ray emission, and magnetic resonance spectroscopic observations. Specifically with respect to quantum chemical studies, the inconclusive energetics for the possible isoforms of S3 is an acute problem that is probably beyond the capabilities of standard density functional theory.
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