Quantum-chemical studies of electron transfer and spectroscopy of mixed-valence systems
Inorganic Molecular Chemistry - Synthesis and Characterisation
Final Report Abstract
Quantum-chemical protocols to describe localization/delocalization in a wide variety of mixedvalence (MV) systems have been generalized, extended, validated and applied to a wide range of questions ranging from organometallic chemistry and molecular electronics to bioinorganic chemistry and molecular magnetism. Improvements of electronic-structure methods in the field have been promoted by setting up a representative benchmark set (MVO-10) of small gas-phase MV oxo systems representing main-group and transition-metal systems, localized and delocalized, as well as oxyl- and metal-centered situations, supported by accurate coupled-cluster calculations. This has allowed the identification of suitable DFT functionals. In particular, the novel LH20t local hybrid functional developed in our group is the first to simultaneously describe the most extreme localized and delocalized cases. It has also been found to perform excellently for the spectroscopic properties of realistic MV systems in solution, opening the door to wide application. Progress has also been made regarding the modelling of the solvent environment (including AIMD simulations and 3D-RISM-SCF methods), but this work is still ongoing. Applications to organometallic molecular wires in collaboration with spectroelectrochemists have provided a host of novel insights regarding the limits of simplified Mulliken-Hush treatments and the necessity of conformational sampling that even may include the simultaneous population of localized and delocalized conformers. A “minimal spectroscopic approach” has been proposed that allows limiting the computational work to a minimal number of conformers in accurately reproducing electronic and vibrational spectra. A class of MV diiron molecular wires has been reclassified as partly localized based on our computations together with spectroelectrochemistry. It was found that the original protocol based on the BLYP35 global hybrid functional reaches its limits in describing the near-IR/UV/vis spectra with localized charge on iron, due to strong spin contamination. Then TDDFT computations with novel local hybrids (such as LH20t) offer substantial improvements, extending the quality of the model. Relativistic two-component procedures have been developed to compute the full anisotropic exchange tensors in exchange-coupled multinuclear transition-metal complexes, including MV systems. This includes anisotropic symmetric exchange, antisymmetric Dzyaloshinskii−Moriya exchange, as well as single-ion zero-field splittings. The many-spin Hamiltonians obtained by these and other means have to be transformed to giant-spin Hamiltonians to compare with spectroscopic data obtained from, e.g., EPR and INS spectroscopies. We have developed powerful methods to perform this van-Vleck transformation, ranging from an extension of perturbational methods to third order all the way to two different methods that for the first time allow an exact diagonalization, making extensive use of point-group and spin-permutation symmetries. Such methods have been applied successfully to the spectroscopy of a range of complicated multinuclear complexes in molecular magnetism, including the so far most complete interpretation of spectroscopy and thermodynamics of the widely studied mixed-valent “Mn12” single-molecule magnets.
Publications
- Quantum-chemical insights into mixed-valence systems: within and beyond the Robin/Day scheme Chem. Soc. Rev. 2014, 43, 5067-5088
M. Parthey, M. Kaupp
(See online at https://doi.org/10.1039/C3CS60481K) - [Al2O4]-, a benchmark gas-phase class II mixed-valence radical anion for the evaluation of quantum-chemical methods J. Chem. Theor. Comput. 2016, 12, 3796-3806
M. Kaupp, A. Karton, F. Bischoff
(See online at https://doi.org/10.1021/acs.jctc.6b00594) - Rational Control of Conformational Distributions and Mixed-Valence Characteristics in Diruthenium Complexes Chem. Eur. J. 2016, 22, 16138-16146
J. B. G. Gluyas, S. Gückel, M. Kaupp, P. J. Low
(See online at https://doi.org/10.1002/chem.201603236) - Understanding Thermodynamic and Spectroscopic Properties of Tetragonal Mn12 Single-Molecule Magnets from Combined DFT/Spin-Hamiltonian Calculations J. Phys. Chem. A 2016, 120, 6864-6879
S. Ghassemi Tabrizi, A. V. Arbuznikov, M. Kaupp
- Exact mapping from Many-Spin Hamiltonians to Giant-Spin Hamiltonians Chem. Eur. J. 2018, 24, 4689-4702
S. Ghassemi Tabrizi, A. V. Arbuznikov, M. Kaupp
(See online at https://doi.org/10.1002/chem.201705897) - Iron versus ruthenium: clarifying the electronic differences between prototypical mixed-valence organometallic butadiyndiyl bridged molecular wires Organometallics 2018, 37, 1432-1445
S. Gückel, J. B. G. Gluyas, S. El-Tarhuni, A. N. Sobolev, M. W. Whiteley, J.-F. Halet, C. Lapinte, M. Kaupp, P. J. Low
(See online at https://doi.org/10.1021/acs.organomet.8b00099) - MVO-10. A gas-phase oxide benchmark for localization/delocalization in mixed-valence systems J. Chem. Theory Comput. 2018, 14, 3512-3523
S. Klawohn, M. Kaupp, A. Karton
(See online at https://doi.org/10.1021/acs.jctc.8b00289) - Noncollinear two-component quasirelativistic description of spin interactions in exchangecoupled systems. Mapping generalized broken-symmetry states to effective spin Hamiltonians Chem. Theory Comput. 2018, 14, 1267-1276
A. Wodyński, M. Kaupp J.
(See online at https://doi.org/10.1021/acs.jctc.7b01067) - A Spectroscopic and Computationally Minimal Approach to the Analysis of Charge‐Transfer Processes in Conformationally Fluxional Mixed‐Valence and Heterobimetallic Complexes Chem. Eur. J. 2019, 25, 8837-8853
J. B. G. Gluyas, S. Gückel, S. G. Eaves, D. S. Yufit, M. Kaupp, P. J. Low
(See online at https://doi.org/10.1002/chem.201901200) - The Hubbard Trimer with Spin-Orbit Coupling: Hartree-Fock Solutions, Anisotropic Spin Hamiltonian, and (Non)collinearity J. Phys. Chem. A 2019, 123, 2361-2378
S. Ghassemi Tabrizi, A. V. Arbuznikov, M. Kaupp
(See online at https://doi.org/10.1021/acs.jpca.8b11959) - Describing the Electronic Properties of Radical-Ligand Coordination Compounds by Four Principal Parameters Dalton Trans 2020, 49, 9735-9742
N. M. Mews, M. Reimann, G. Hörner, H. Schubert, M. Kaupp, A. Berkefeld
(See online at https://doi.org/10.1039/D0DT02237C) - Iron versus Ruthenium: Evidence for the distinct differences in the electronic structures of hexa-1,3,5-triyn-1,6-diyl-bridged complexes [Cp*(dppe)M}{µ-(C=C)3}{M(dppe)Cp*}]+ (M= Fe, Ru). Organometallics 2020, 40, 346-357
S. Gückel, P. Safari, M. H. Ghazvini, J. B.G. Gluyas, M. Kaupp, P. J. Low
(See online at https://doi.org/10.1021/acs.organomet.0c00681)
