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Applying Unconventional Spectroscopies to the Single‐Molecule Magnets, Co(PPh 3 ) 2 X 2 (X=Cl, Br, I): Unveiling Magnetic Transitions and Spin‐Phonon Coupling
Author(s) -
Bone Alexandria N.,
Widener Chelsea N.,
Moseley Duncan H.,
Liu Zhiming,
Lu Zhengguang,
Cheng Yongqiang,
Daemen Luke L.,
Ozerov Mykhaylo,
Telser Joshua,
Thirunavukkuarasu Komalavalli,
Smirnov Dmitry,
Greer Samuel M.,
Hill Stephen,
Krzystek J.,
Holldack Karsten,
Aliabadi Azar,
Schnegg Alexander,
Dunbar Kim R.,
Xue ZiLing
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202100705
Subject(s) - phonon , condensed matter physics , relaxation (psychology) , spin (aerodynamics) , density functional theory , coupling (piping) , inelastic neutron scattering , electron paramagnetic resonance , chemistry , materials science , physics , nuclear magnetic resonance , scattering , neutron scattering , computational chemistry , quantum mechanics , psychology , social psychology , metallurgy , thermodynamics
Large separation of magnetic levels and slow relaxation in metal complexes are desirable properties of single‐molecule magnets (SMMs). Spin‐phonon coupling (interactions of magnetic levels with phonons) is ubiquitous, leading to magnetic relaxation and loss of memory in SMMs and quantum coherence in qubits. Direct observation of magnetic transitions and spin‐phonon coupling in molecules is challenging. We have found that far‐IR magnetic spectra (FIRMS) of Co(PPh 3 ) 2 X 2 ( Co‐X ; X=Cl, Br, I) reveal rarely observed spin‐phonon coupling as avoided crossings between magnetic and u ‐symmetry phonon transitions. Inelastic neutron scattering (INS) gives phonon spectra. Calculations using VASP and phonopy programs gave phonon symmetries and movies. Magnetic transitions among zero‐field split (ZFS) levels of the S =3/2 electronic ground state were probed by INS, high‐frequency and ‐field EPR (HFEPR), FIRMS, and frequency‐domain FT terahertz EPR (FD‐FT THz‐EPR), giving magnetic excitation spectra and determining ZFS parameters ( D, E ) and g values. Ligand‐field theory (LFT) was used to analyze earlier electronic absorption spectra and give calculated ZFS parameters matching those from the experiments. DFT calculations also gave spin densities in Co‐X , showing that the larger Co(II) spin density in a molecule, the larger its ZFS magnitude. The current work reveals dynamics of magnetic and phonon excitations in SMMs. Studies of such couplings in the future would help to understand how spin‐phonon coupling may lead to magnetic relaxation and develop guidance to control such coupling.