In-depth investigation of large axial magnetic anisotropy in monometallic 3d complexes using frequency domain magnetic resonance and ab initio methods: a study of trigonal bipyramidal Co(ii)

Moya A. Hay, Arup Sarkar, Gavin A. Craig, Lakshmi Bhaskaran, Joscha Nehrkorn, Mykhailo Ozerov, Katie E. R. Marriott, Claire Wilson, Gopalan Rajaraman, Stephen Hill, Mark Murrie

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

The magnetic properties of 3d monometallic complexes can be tuned through geometric control, owing to their synthetic accessibility and relative structural simplicity. Monodentate ligands offer great potential for fine-tuning the coordination environment to engineer both the axial and rhombic zero-field splitting (ZFS) parameters. In [CoCl3(DABCO)(HDABCO)] (1), the trigonal bipyramidal Co(ii) centre has two bulky axial ligands and three equatorial chloride ligands. An in-depth experimental and theoretical study of 1 reveals a large easy-plane magnetic anisotropy (+ve D) with a negligible rhombic zero-field splitting (E) due to the strict axial symmetry imposed by the C3 symmetric ligand and trigonal space group. The large easy-plane magnetic anisotropy (D = +44.5 cm−1) is directly deduced using high-field EPR and frequency-domain magnetic resonance (FDMR) studies. Ab initio calculations reveal a large positive contribution to the D term arising from ground state/excited state mixing of the 4E′′ states at ∼4085 cm−1 and a minor contribution from the spin–flip transition as well. The nature of the slow relaxation in 1 is elucidated through analysis of the rates of relaxation of magnetisation, taking into account Raman and direct spin–lattice relaxation processes and Quantum Tunnelling of the Magnetisation (QTM). The terms relating to the direct process and QTM were found based on the fit of the field-dependence of τ at 2 K. Subsequently, these were used as fixed parameters in the fit of the temperature-dependence of τ to obtain the Raman terms. This experimental–theoretical investigation provides further insight into the power of FDMR and ab initio methods for the thorough investigation of magnetic anisotropy. Thus, these results contribute to design criteria for high magnetic anisotropy systems.
LanguageEnglish
Pages6354-6361
Number of pages8
JournalChemical Science
Volume10
Issue number25
Early online date20 May 2019
DOIs
Publication statusPublished - 7 Jul 2019

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Magnetic anisotropy
Magnetic resonance
Ligands
Magnetization
Spin-lattice relaxation
Relaxation processes
Excited states
Ground state
Paramagnetic resonance
Chlorides
Magnetic properties
Tuning
Engineers
Temperature

Keywords

  • 3d monometallic complexes
  • monodentate ligands
  • single-molecule magnets
  • SMMs

Cite this

Hay, Moya A. ; Sarkar, Arup ; Craig, Gavin A. ; Bhaskaran, Lakshmi ; Nehrkorn, Joscha ; Ozerov, Mykhailo ; Marriott, Katie E. R. ; Wilson, Claire ; Rajaraman, Gopalan ; Hill, Stephen ; Murrie, Mark. / In-depth investigation of large axial magnetic anisotropy in monometallic 3d complexes using frequency domain magnetic resonance and ab initio methods: a study of trigonal bipyramidal Co(ii). In: Chemical Science. 2019 ; Vol. 10, No. 25. pp. 6354-6361.
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abstract = "The magnetic properties of 3d monometallic complexes can be tuned through geometric control, owing to their synthetic accessibility and relative structural simplicity. Monodentate ligands offer great potential for fine-tuning the coordination environment to engineer both the axial and rhombic zero-field splitting (ZFS) parameters. In [CoCl3(DABCO)(HDABCO)] (1), the trigonal bipyramidal Co(ii) centre has two bulky axial ligands and three equatorial chloride ligands. An in-depth experimental and theoretical study of 1 reveals a large easy-plane magnetic anisotropy (+ve D) with a negligible rhombic zero-field splitting (E) due to the strict axial symmetry imposed by the C3 symmetric ligand and trigonal space group. The large easy-plane magnetic anisotropy (D = +44.5 cm−1) is directly deduced using high-field EPR and frequency-domain magnetic resonance (FDMR) studies. Ab initio calculations reveal a large positive contribution to the D term arising from ground state/excited state mixing of the 4E′′ states at ∼4085 cm−1 and a minor contribution from the spin–flip transition as well. The nature of the slow relaxation in 1 is elucidated through analysis of the rates of relaxation of magnetisation, taking into account Raman and direct spin–lattice relaxation processes and Quantum Tunnelling of the Magnetisation (QTM). The terms relating to the direct process and QTM were found based on the fit of the field-dependence of τ at 2 K. Subsequently, these were used as fixed parameters in the fit of the temperature-dependence of τ to obtain the Raman terms. This experimental–theoretical investigation provides further insight into the power of FDMR and ab initio methods for the thorough investigation of magnetic anisotropy. Thus, these results contribute to design criteria for high magnetic anisotropy systems.",
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In-depth investigation of large axial magnetic anisotropy in monometallic 3d complexes using frequency domain magnetic resonance and ab initio methods: a study of trigonal bipyramidal Co(ii). / Hay, Moya A.; Sarkar, Arup; Craig, Gavin A.; Bhaskaran, Lakshmi; Nehrkorn, Joscha; Ozerov, Mykhailo; Marriott, Katie E. R.; Wilson, Claire; Rajaraman, Gopalan; Hill, Stephen; Murrie, Mark.

In: Chemical Science, Vol. 10, No. 25, 07.07.2019, p. 6354-6361.

Research output: Contribution to journalArticle

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T1 - In-depth investigation of large axial magnetic anisotropy in monometallic 3d complexes using frequency domain magnetic resonance and ab initio methods: a study of trigonal bipyramidal Co(ii)

AU - Hay, Moya A.

AU - Sarkar, Arup

AU - Craig, Gavin A.

AU - Bhaskaran, Lakshmi

AU - Nehrkorn, Joscha

AU - Ozerov, Mykhailo

AU - Marriott, Katie E. R.

AU - Wilson, Claire

AU - Rajaraman, Gopalan

AU - Hill, Stephen

AU - Murrie, Mark

PY - 2019/7/7

Y1 - 2019/7/7

N2 - The magnetic properties of 3d monometallic complexes can be tuned through geometric control, owing to their synthetic accessibility and relative structural simplicity. Monodentate ligands offer great potential for fine-tuning the coordination environment to engineer both the axial and rhombic zero-field splitting (ZFS) parameters. In [CoCl3(DABCO)(HDABCO)] (1), the trigonal bipyramidal Co(ii) centre has two bulky axial ligands and three equatorial chloride ligands. An in-depth experimental and theoretical study of 1 reveals a large easy-plane magnetic anisotropy (+ve D) with a negligible rhombic zero-field splitting (E) due to the strict axial symmetry imposed by the C3 symmetric ligand and trigonal space group. The large easy-plane magnetic anisotropy (D = +44.5 cm−1) is directly deduced using high-field EPR and frequency-domain magnetic resonance (FDMR) studies. Ab initio calculations reveal a large positive contribution to the D term arising from ground state/excited state mixing of the 4E′′ states at ∼4085 cm−1 and a minor contribution from the spin–flip transition as well. The nature of the slow relaxation in 1 is elucidated through analysis of the rates of relaxation of magnetisation, taking into account Raman and direct spin–lattice relaxation processes and Quantum Tunnelling of the Magnetisation (QTM). The terms relating to the direct process and QTM were found based on the fit of the field-dependence of τ at 2 K. Subsequently, these were used as fixed parameters in the fit of the temperature-dependence of τ to obtain the Raman terms. This experimental–theoretical investigation provides further insight into the power of FDMR and ab initio methods for the thorough investigation of magnetic anisotropy. Thus, these results contribute to design criteria for high magnetic anisotropy systems.

AB - The magnetic properties of 3d monometallic complexes can be tuned through geometric control, owing to their synthetic accessibility and relative structural simplicity. Monodentate ligands offer great potential for fine-tuning the coordination environment to engineer both the axial and rhombic zero-field splitting (ZFS) parameters. In [CoCl3(DABCO)(HDABCO)] (1), the trigonal bipyramidal Co(ii) centre has two bulky axial ligands and three equatorial chloride ligands. An in-depth experimental and theoretical study of 1 reveals a large easy-plane magnetic anisotropy (+ve D) with a negligible rhombic zero-field splitting (E) due to the strict axial symmetry imposed by the C3 symmetric ligand and trigonal space group. The large easy-plane magnetic anisotropy (D = +44.5 cm−1) is directly deduced using high-field EPR and frequency-domain magnetic resonance (FDMR) studies. Ab initio calculations reveal a large positive contribution to the D term arising from ground state/excited state mixing of the 4E′′ states at ∼4085 cm−1 and a minor contribution from the spin–flip transition as well. The nature of the slow relaxation in 1 is elucidated through analysis of the rates of relaxation of magnetisation, taking into account Raman and direct spin–lattice relaxation processes and Quantum Tunnelling of the Magnetisation (QTM). The terms relating to the direct process and QTM were found based on the fit of the field-dependence of τ at 2 K. Subsequently, these were used as fixed parameters in the fit of the temperature-dependence of τ to obtain the Raman terms. This experimental–theoretical investigation provides further insight into the power of FDMR and ab initio methods for the thorough investigation of magnetic anisotropy. Thus, these results contribute to design criteria for high magnetic anisotropy systems.

KW - 3d monometallic complexes

KW - monodentate ligands

KW - single-molecule magnets

KW - SMMs

U2 - 10.1039/C9SC00987F

DO - 10.1039/C9SC00987F

M3 - Article

VL - 10

SP - 6354

EP - 6361

JO - Chemical Science

T2 - Chemical Science

JF - Chemical Science

SN - 2041-6520

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ER -