Probing the Influence of the Ligands on the Magnetism of Dinuclear Manganese, Iron, and Chromium Complexes Supported by Aroylhydrazone

Domingo, Alex; Specklin, David; Rosa, Vítor; Mameri, Samir; Robert, Vincent; Welter, Richard

doi:10.1002/ejic.201402084

Cited by 9 publications

(4 citation statements)

References 46 publications

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“…The ability to treat large active spaces enables one to study how the computed exchange coupling responds to explicit inclusion of specific orbital sets in the active space–in the present case, of orbitals localized on the bridging ligands. This approach has been suggested in the past 102 and was used in the DMRG framework in the study of the bis-μ-oxo/μ-acetato manganese dimer mentioned above. 61 In that case the metal-only active space DMRG-SCF calculations predicted practically no magnetic coupling.…”

Section: Resultsmentioning

confidence: 99%

Meeting the Challenge of Magnetic Coupling in a Triply-Bridged Chromium Dimer: Complementary Broken-Symmetry Density Functional Theory and Multireference Density Matrix Renormalization Group Perspectives

Pantazis

2019

J. Chem. Theory Comput.

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Face-sharing octahedral dinuclear Cr(III) compounds with d 3 –d 3 electronic configurations represent nontrivial examples of electronic complexity, posing particular challenges for theoretical and computational studies. A tris-hydroxy-bridged Cr(III)–Cr(III) system has proven to be a richly rewarding target for studies of magnetism and electron paramagnetic resonance spectroscopy. It was also reported to be a peculiarly difficult system to treat with density functional theory (DFT). In this work the magnetic coupling problem for this dimer is approached with broken-symmetry (BS)-DFT and multireference calculations that utilize the density matrix renormalization group (DMRG) to handle full-valence active spaces. BS-DFT is shown to recover the correct ordering and energy spacing of Heisenberg spin states if used in conjunction with appropriate spin projection procedures, albeit with pronounced functional sensitivity. The contrasting conclusions of previous studies are traced to incorrect inclusion of electronically excited configurations. Analysis of the direct and differential overlap of corresponding orbital pairs from the BS-DFT solution indicates that metal–metal through-space interaction is the dominant contributor to antiferromagnetic coupling. At the DFT level a procedure that utilizes pseudopotential substitution is demonstrated that allows evaluation of the direct exchange vs superexchange contributions. A complementary description is obtained with DMRG-SCF calculations that enable state-averaged CASSCF calculations with both metal and bridge orbitals in the active space. A localized orbital subspace analysis supports the DFT conclusions that in contrast to doubly bridged isoelectronic analogues, antiferromagnetic coupling in the chromium dimer arises primarily from direct metal–metal interaction but is significantly enhanced by ligand-mediated superexchange.

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Section: Resultsmentioning

confidence: 99%

Meeting the Challenge of Magnetic Coupling in a Triply-Bridged Chromium Dimer: Complementary Broken-Symmetry Density Functional Theory and Multireference Density Matrix Renormalization Group Perspectives

Pantazis

2019

J. Chem. Theory Comput.

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“…This takes the form of the analysis of exchange pathways by comparing the effect of including or excluding localized orbital subspaces within the CAS. This approach is of course entirely general and has been used independently of DMRG, but DMRG allows its extension to larger and more complex systems because the limitations in the number and type of bridging ligands that can be treated in a CASSCF approach are significantly relaxed. For example, most studies discussed above demonstrated that the inclusion of bridging oxo orbitals turns on the superexchange interaction that stabilizes the antiferromagnetic ground state.…”

Section: Exchange‐coupled Systemsmentioning

confidence: 99%

Multireference Approaches to Spin‐State Energetics of Transition Metal Complexes Utilizing the Density Matrix Renormalization Group

Roemelt

Pantazis

2019

Advcd Theory and Sims

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The accurate and reliable calculation of different electronic states in transition metal systems is a persistent challenge for theoretical chemistry. The widespread use of density functional theory for computing the relative energies of states with different spin in transition metal complexes not only has not discouraged, but often, owing to its limitations, has motivated the development and refinement of first-principles wavefunction-based methods, including both single-reference and multireference approaches. A significant boost for the latter has been the emergence of the density matrix renormalization group (DMRG) as a reliable tool in applied quantum chemistry. By enabling the use of larger active spaces than conventionally possible, DMRG has opened up areas of transition metal chemistry that were previously inaccessible to multireference approaches. The present perspective provides an overview of representative studies that make use of DMRG methods and discusses recent applications to spin-state energetics of transition metal systems. These range from mononuclear to exchange-coupled systems that define an important emerging field of DMRG applications. Major achievements are highlighted and potential pitfalls are identified with a view toward future methodological developments as well as extensions in the applicability of DMRG-based approaches to problems of spin-state energetics and exchange-coupling in transition metal chemistry.

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“…The canonical MOs are transformed by following a valence-bond-like description of the electronic density, which is based on one of the Kekulé structures of the molecule and allows us to spatially separate the orbitals [153,[274][275][276]. The method has proven to be extremely e cient not only to reduce in a rational way the number of inactive and virtual MOs in post CASSCF treatments [277][278][279][280], but also to analyze the relevance of chemical regions in energy di↵erences [281].…”

Section: Universitat Rovira I Virgili From Mononuclear To Dinuclear: mentioning

confidence: 99%

“…Amidinium-containing cations may o↵er a possibility to test the proposed magneto-structural correlation since they are known to be active H-bonds donors and o↵er numerous possibilities of functionalization [303][304][305][306]. Theoreticians have reported, since the first application to magnetic ordering in transition metal compounds done by Wachters and Nieuwpoort in 1972 [307], accurate strategies for analyzing the exchange coupling constants in bimetallic complexes with bridging ligands through ab initio calculations [105,109,110,114,280,308,309].…”

Section: Introductionmentioning

confidence: 99%

From Mononuclear to Dinuclear: Magnetic Properties of Transition Metal Complexes

Saureu¹

2016

ioChem-BD Computational Chemistry Datasets

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Probing the Influence of the Ligands on the Magnetism of Dinuclear Manganese, Iron, and Chromium Complexes Supported by Aroylhydrazone

Cited by 9 publications

References 46 publications

Meeting the Challenge of Magnetic Coupling in a Triply-Bridged Chromium Dimer: Complementary Broken-Symmetry Density Functional Theory and Multireference Density Matrix Renormalization Group Perspectives

Meeting the Challenge of Magnetic Coupling in a Triply-Bridged Chromium Dimer: Complementary Broken-Symmetry Density Functional Theory and Multireference Density Matrix Renormalization Group Perspectives

Multireference Approaches to Spin‐State Energetics of Transition Metal Complexes Utilizing the Density Matrix Renormalization Group

From Mononuclear to Dinuclear: Magnetic Properties of Transition Metal Complexes

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