Hay, M. A., Craig, G. A., Bhaskaran, L., Nehrkorn, J., Ozerov, M., Marriott, K. E.R., Wilson, C. , Rajaraman, G., Hill, S. and Murrie, M. (2019) 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). Chemical Science, 10(25), pp. 6354-6361. (doi: 10.1039/C9SC00987F) (PMID:31341591) (PMCID:PMC6601423)
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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.
| Item Type: | Articles |
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| Additional Information: | A portion of this work was performed at the NHMFL, which is supported by the NSF (DMR-1157490 and DMR-1644779) and the State of Florida. SH also acknowledges the support of the NSF (DMR-1610226) and the DOE (Award number DE-SC0019330). GR would like to thank SERB for funding (CRG/2018/000430). AS thanks CSIR for a SRF fellowship. |
| Status: | Published |
| Refereed: | Yes |
| Glasgow Author(s) Enlighten ID: | Wilson, Dr Claire and Craig, Dr Gavin and Marriott, Miss Katie and Hay, Ms Moya Anne and Murrie, Professor Mark |
| Authors: | Hay, M. A., Craig, G. A., Bhaskaran, L., Nehrkorn, J., Ozerov, M., Marriott, K. E.R., Wilson, C., Rajaraman, G., Hill, S., and Murrie, M. |
| College/School: | College of Science and Engineering > School of Chemistry |
| Journal Name: | Chemical Science |
| Publisher: | Royal Society of Chemistry |
| ISSN: | 2041-6520 |
| ISSN (Online): | 2041-6539 |
| Published Online: | 20 May 2019 |
| Copyright Holders: | Copyright © 2019 The Authors |
| First Published: | First published in Chemical Science 10(25): 6354-6361 |
| Publisher Policy: | Reproduced under a Creative Commons License |
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