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Spin-Phonon Coupling and Dynamic Zero-Field Splitting Contributions to Spin Conversion Processes in Iron(II) Complexes

Higdon, Nicholas J. and Barth, Alexandra T. and Kozlowski, Patryk T. and Hadt, Ryan G. (2020) Spin-Phonon Coupling and Dynamic Zero-Field Splitting Contributions to Spin Conversion Processes in Iron(II) Complexes. Journal of Chemical Physics, 152 (20). Art. No. 204306. ISSN 0021-9606.

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Magnetization dynamics of transition metal complexes manifest in properties and phenomena of fundamental and applied interest [e.g., slow magnetic relaxation in single molecule magnets, quantum coherence in quantum bits (qubits), and intersystem crossing (ISC) rates in photophysics]. While spin–phonon coupling is recognized as an important determinant of these dynamics, additional fundamental studies are required to unravel the nature of the coupling and, thus, leverage it in molecular engineering approaches. To this end, we describe here a combined ligand field theory and multireference ab initio model to define spin–phonon coupling terms in S = 2 transition metal complexes and demonstrate how couplings originate from both the static and dynamic properties of ground and excited states. By extending concepts to spin conversion processes, ligand field dynamics manifest in the evolution of the excited state origins of zero-field splitting (ZFS) along specific normal mode potential energy surfaces. Dynamic ZFSs provide a powerful means to independently evaluate contributions from spin-allowed and/or spin-forbidden excited states to spin–phonon coupling terms. Furthermore, ratios between various intramolecular coupling terms for a given mode drive spin conversion processes in transition metal complexes and can be used to analyze the mechanisms of ISC. Variations in geometric structure strongly influence the relative intramolecular linear spin–phonon coupling terms and will define the overall spin state dynamics. While the findings of this study are of general importance for understanding magnetization dynamics, they also link the phenomenon of spin–phonon coupling across fields of single molecule magnetism, quantum materials/qubits, and transition metal photophysics.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Higdon, Nicholas J.0000-0002-5806-1151
Barth, Alexandra T.0000-0002-1813-4029
Hadt, Ryan G.0000-0001-6026-1358
Additional Information:© 2020 Published under license by AIP Publishing. Submitted: 2 March 2020; Accepted: 7 May 2020; Published Online: 27 May 2020. The authors acknowledge Dr. Jay Winkler for helpful discussions and Dr. Martin Srnec for assistance with initial CASSCF/NEVPT2 calculations. A.T.B. acknowledges funding through a National Science Foundation Graduate Research Fellowship (NSF Grant No. DGE-1745301). P.T.K. acknowledges funding through the Caltech Summer Undergraduate Research Fellowship (SURF) program. Financial support from Caltech and the Dow Next Generation Educator Fund is gratefully acknowledged. Data Availability: The data that support the findings of this study are available from the corresponding author upon reasonable request.
Funding AgencyGrant Number
NSF Graduate Research FellowshipDGE-1745301
Caltech Summer Undergraduate Research Fellowship (SURF)UNSPECIFIED
Dow Next Generation Educator FundUNSPECIFIED
Subject Keywords:intersystem crossing (ISC); zero-field splitting; photosensitizers; magnetization dynamics; ligand field theory; ab initio calculation; photomagnetism; spin-phonon coupling; photophysics
Issue or Number:20
Record Number:CaltechAUTHORS:20200303-160403611
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:101688
Deposited By: Tony Diaz
Deposited On:04 Mar 2020 03:44
Last Modified:02 Jun 2021 19:31

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