1
|
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.
Collapse
Affiliation(s)
- Ursula Rastetter
- Department of Chemistry, University of Hamburg, Hamburg, Germany
| | | | - Carmen Herrmann
- Department of Chemistry, University of Hamburg, Hamburg, Germany
| |
Collapse
|
2
|
Schmid P, Fantuzzi F, Klopf J, Schröder NB, Dewhurst RD, Braunschweig H, Engel V, Engels B. Twisting versus Delocalization in CAAC- and NHC-Stabilized Boron-Based Biradicals: The Roles of Sterics and Electronics. Chemistry 2021; 27:5160-5170. [PMID: 33225473 PMCID: PMC8048672 DOI: 10.1002/chem.202004619] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 11/12/2020] [Indexed: 11/06/2022]
Abstract
Twisted boron-based biradicals featuring unsaturated C2 R2 (R=Et, Me) bridges and stabilization by cyclic (alkyl)(amino)carbenes (CAACs) were recently prepared. These species show remarkable geometrical and electronic differences with respect to their unbridged counterparts. Herein, a thorough computational investigation on the origin of their distinct electrostructural properties is performed. It is shown that steric effects are mostly responsible for the preference for twisted over planar structures. The ground-state multiplicity of the twisted structure is modulated by the σ framework of the bridge, and different R groups lead to distinct multiplicities. In line with the experimental data, a planar structure driven by delocalization effects is observed as global minimum for R=H. The synthetic elusiveness of C2 R2 -bridged systems featuring N-heterocyclic carbenes (NHCs) was also investigated. These results could contribute to the engineering of novel main group biradicals.
Collapse
Affiliation(s)
- Paul Schmid
- Institute for Physical and Theoretical ChemistryJulius-Maximilians-Universität WürzburgEmil-Fischer-Strasse 4297074WürzburgGermany
| | - Felipe Fantuzzi
- Institute for Physical and Theoretical ChemistryJulius-Maximilians-Universität WürzburgEmil-Fischer-Strasse 4297074WürzburgGermany
- Institute for Inorganic ChemistryJulius-Maximilians-Universität WürzburgAm Hubland97074WürzburgGermany
- Institute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität WürzburgAm Hubland97074WürzburgGermany
| | - Jonas Klopf
- Institute for Physical and Theoretical ChemistryJulius-Maximilians-Universität WürzburgEmil-Fischer-Strasse 4297074WürzburgGermany
| | - Niklas B. Schröder
- Institute for Physical and Theoretical ChemistryJulius-Maximilians-Universität WürzburgEmil-Fischer-Strasse 4297074WürzburgGermany
| | - Rian D. Dewhurst
- Institute for Inorganic ChemistryJulius-Maximilians-Universität WürzburgAm Hubland97074WürzburgGermany
- Institute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität WürzburgAm Hubland97074WürzburgGermany
| | - Holger Braunschweig
- Institute for Inorganic ChemistryJulius-Maximilians-Universität WürzburgAm Hubland97074WürzburgGermany
- Institute for Sustainable Chemistry & Catalysis with BoronJulius-Maximilians-Universität WürzburgAm Hubland97074WürzburgGermany
| | - Volker Engel
- Institute for Physical and Theoretical ChemistryJulius-Maximilians-Universität WürzburgEmil-Fischer-Strasse 4297074WürzburgGermany
| | - Bernd Engels
- Institute for Physical and Theoretical ChemistryJulius-Maximilians-Universität WürzburgEmil-Fischer-Strasse 4297074WürzburgGermany
| |
Collapse
|
3
|
Pylaeva S, Marx P, Singh G, Kühne TD, Roemelt M, Elgabarty H. Organic Mixed-Valence Compounds and the Overhauser Effect in Insulating Solids. J Phys Chem A 2021; 125:867-874. [PMID: 33464904 DOI: 10.1021/acs.jpca.0c11296] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Recent experiments have shown that the organic free radical 1,3-bisdiphenylene-2-phenylallyl (BDPA) can induce an Overhauser effect dynamic nuclear polarization in insulating solids, a feat previously considered not to be possible. Here, we establish that this peculiar ability of the BDPA radical stems from its mixed-valence nature and the ensuing intramolecular charge transfer. Using state-of-the-art DMRGSCF calculations, we confirm the class II mixed-valence nature of BDPA with the characteristic double-well potential energy surface, and we investigate the mechanism of the consequent electron hopping. A two-component vibronic Hamiltonian is then employed to compute the rate of electron hopping from a quantum dynamical time-propagation of the density matrix. The predicted hyperfine coupling oscillations indeed fall within the frequency range required for an Overhauser effect. The paradigm of mixed-valence compounds as a mining source opens many possibilities for the development and fine tuning of novel polarizing agents.
Collapse
Affiliation(s)
- Svetlana Pylaeva
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, Chair of Theoretical Chemistry, University of Paderborn, Warburger Str. 100, Paderborn 33098, Germany
| | - Patrick Marx
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Gurjot Singh
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Thomas D Kühne
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, Chair of Theoretical Chemistry, University of Paderborn, Warburger Str. 100, Paderborn 33098, Germany
| | - Michael Roemelt
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, D-44780 Bochum, Germany
| | - Hossam Elgabarty
- Dynamics of Condensed Matter and Center for Sustainable Systems Design, Chair of Theoretical Chemistry, University of Paderborn, Warburger Str. 100, Paderborn 33098, Germany
| |
Collapse
|
4
|
Kröncke S, Herrmann C. Toward a First-Principles Evaluation of Transport Mechanisms in Molecular Wires. J Chem Theory Comput 2020; 16:6267-6279. [PMID: 32886502 DOI: 10.1021/acs.jctc.0c00667] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Understanding charge transport through molecular wires is important for nanoscale electronics and biochemistry. Our goal is to establish a simple first-principles protocol for predicting the charge transport mechanism in such wires, in particular the crossover from coherent tunneling for short wires to incoherent hopping for longer wires. This protocol is based on a combination of density functional theory with a polarizable continuum model introduced by Kaupp et al. for mixed-valence molecules, which we had previously found to work well for length-dependent charge delocalization in such systems. We combine this protocol with a new charge delocalization measure tailored for molecular wires, and we show that it can predict the tunneling-to-hopping transition length with a maximum error of one subunit in five sets of molecular wires studied experimentally in molecular junctions at room temperature. This suggests that the protocol is also well suited for estimating the extent of hopping sites as relevant, for example, for the intermediate tunneling-hopping regime in DNA.
Collapse
Affiliation(s)
- Susanne Kröncke
- Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| | - Carmen Herrmann
- Department of Chemistry, University of Hamburg, Martin-Luther-King-Platz 6, 20146 Hamburg, Germany
| |
Collapse
|
5
|
Borovkov VI, Potashov PA, Beregovaya IV, Shchegoleva LN, Molin YN. Primary Radical Cations in Irradiated Poly(isobutylene). J Phys Chem B 2020; 124:7059-7066. [PMID: 32678602 DOI: 10.1021/acs.jpcb.0c03280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Using the method of time-resolved magnetic field effect in radiation-induced fluorescence, primary radical cations (RCs) in irradiated poly(isobutylene) (PIB) have been detected for the first time. A comparison of experimental results with the data of quantum chemical calculations suggests that the initial geometry of the ionized fragment of the PIB molecule is close to the geometry of the neutral polymer in the trans-gauche-trans-gauche conformation. The spin density of the RC in this geometry is delocalized over more than 10 polymer units, and the width of the RC's EPR spectrum is about ΔHpp ≈ 1.3 mT. At a temperature of 273 K and lower, the lifetime of the primary RCs with the delocalized spin density exceeds 10 ns. The structural relaxation of the RCs results in the spin density localization on a single C-C bond, which is extended to nearly 0.2 nm, and in the increase in the EPR spectrum width to ΔHpp ≈ 2.4 mT. It looks likely that this intramolecular structural relaxation is coupled strongly with those types of molecular motions that determine the process of dielectric β-relaxation in the polymer.
Collapse
Affiliation(s)
- Vsevolod I Borovkov
- Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, 3, Institutskaya str., 630090 Novosibirsk, Russia.,Novosibirsk State University, 2, Pirogova str., Novosibirsk 630090, Russia
| | - Pavel A Potashov
- Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, 3, Institutskaya str., 630090 Novosibirsk, Russia.,Novosibirsk State University, 2, Pirogova str., Novosibirsk 630090, Russia
| | - Irina V Beregovaya
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9, Akad. Lavrent'ev Avenue, Novosibirsk 630090, Russia
| | - Lyudmila N Shchegoleva
- N. N. Vorozhtsov Novosibirsk Institute of Organic Chemistry, SB RAS, 9, Akad. Lavrent'ev Avenue, Novosibirsk 630090, Russia
| | - Yuri N Molin
- Voevodsky Institute of Chemical Kinetics and Combustion, SB RAS, 3, Institutskaya str., 630090 Novosibirsk, Russia
| |
Collapse
|
6
|
Affiliation(s)
- Jean-Pierre Launay
- CEMES-CNRS; Université de Toulouse; 29 rue Jeanne Marvig 31055 Toulouse France
| |
Collapse
|
7
|
Herrmann C. Electronic Communication as a Transferable Property of Molecular Bridges? J Phys Chem A 2019; 123:10205-10223. [PMID: 31380640 DOI: 10.1021/acs.jpca.9b05618] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Electronic communication through molecular bridges is important for different types of experiments, such as single-molecule conductance, electron transfer, superexchange spin coupling, and intramolecular singlet fission. In many instances, the chemical structure of the bridge determines how the two parts it is connecting communicate, and does so in ways that are transferable between these different manifestations (for example, high conductance often correlates with strong antiferromagnetic spin coupling, and low conductance due to destructive quantum interference correlates with ferromagnetic coupling). Defining electronic communication as a transferable property of the bridge can help transfer knowledge between these different areas of research. Examples and limits of such transferability are discussed here, along with some possible directions for future research, such as employing spin-coupled and mixed-valence systems as structurally well-controlled proxies for understanding molecular conductance and for validating first-principles theoretical methodologies, building conceptual understanding for the growing experimental work on intramolecular singlet fission, and developing measures for the transferability of electronic communication as a bridge property.
Collapse
Affiliation(s)
- Carmen Herrmann
- Department of Chemistry , University of Hamburg , Martin-Luther-King-Platz 6 , Hamburg 20146 , Germany
| |
Collapse
|
8
|
Stuyver T, Chen B, Zeng T, Geerlings P, De Proft F, Hoffmann R. Do Diradicals Behave Like Radicals? Chem Rev 2019; 119:11291-11351. [DOI: 10.1021/acs.chemrev.9b00260] [Citation(s) in RCA: 139] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Thijs Stuyver
- Algemene Chemie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Bo Chen
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca New York 14853, United States
| | - Tao Zeng
- Department of Chemistry, York University, Toronto, Ontario M3J1P3, Canada
- Department of Chemistry, Carleton University, Ottawa, Ontario K1S5B6, Canada
| | - Paul Geerlings
- Algemene Chemie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Frank De Proft
- Algemene Chemie, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Brussels, Belgium
| | - Roald Hoffmann
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca New York 14853, United States
| |
Collapse
|