Single-ion anisotropy and exchange coupling in cobalt( ii )-radical complexes: insights from magnetic and ab initio studies

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dc.contributor.authorGransbury, GKen_AU
dc.contributor.authorBoulon, MEen_AU
dc.contributor.authorMole, RAen_AU
dc.contributor.authorGable, RWen_AU
dc.contributor.authorMoubaraki, Ben_AU
dc.contributor.authorMurray, KSen_AU
dc.contributor.authorSorace, Len_AU
dc.contributor.authorSoncini, Aen_AU
dc.contributor.authorBoskovic, Cen_AU
dc.date.accessioned2024-10-03T23:25:43Zen_AU
dc.date.available2024-10-03T23:25:43Zen_AU
dc.date.issued2019-10-07en_AU
dc.date.statistics2024-09-25en_AU
dc.description.abstractThe concurrent effects of single-ion anisotropy and exchange interactions on the electronic structure and magnetization dynamics have been analyzed for a cobalt(II)-semiquinonate complex. Analogs containing diamagnetic catecholate and tropolonate ligands were employed for comparison of the magnetic behavior and zinc congeners assisted with the spectroscopic characterization and assessment of intermolecular interactions in the cobalt(II) compounds. Low temperature X-band (ν ≈ 9.4 GHz) and W-Band (ν ≈ 94 GHz) electron paramagnetic resonance spectroscopy and static and dynamic magnetic measurements have been used to elucidate the electronic structure of the high spin cobalt(II) ion in [Co(Me3tpa)(Br4cat)] (1; Me3tpa = tris[(6-methyl-2-pyridyl)methyl]amine, Br4cat2− = tetrabromocatecholate) and [Co(Me3tpa)(trop)](PF6) (2(PF6); trop− = tropolonate), which show slow relaxation of the magnetization in applied field. The cobalt(II)-semiquinonate exchange interaction in [Co(Me3tpa)(dbsq)](PF6)·tol (3(PF6)·tol; dbsq− = 3,5-di-tert-butylsemiquinonate, tol = toluene) has been determined using an anisotropic exchange Hamiltonian in conjunction with multistate restricted active space self-consistent field ab initio modeling and wavefunction analysis, with comparison to magnetic and inelastic neutron scattering data. Our results demonstrate dominant ferromagnetic exchange for 3+ that is of similar magnitude to the anisotropy parameters of the cobalt(II) ion and contains a significant contribution from spin–orbit coupling. The nature of the exchange coupling between octahedral high spin cobalt(II) and semiquinonate ligands is a longstanding question; answering this question for the specific case of 3+ has confirmed the considerable sensitivity of the exchange to the molecular structure. The methodology employed will be generally applicable for elucidating exchange coupling between orbitally-degenerate metal ions and radical ligands and relevant to the development of bistable molecules and their integration into devices. © The Royal Society of Chemistry 2019. Open Access CC-NCen_AU
dc.description.sponsorshipWe thank the Australian Research Council for financial support to CB and LS through DP150100353. GKG acknowledges the support of an Elizabeth and Vernon Puzey Scholarship from the University of Melbourne and an Australian Government Research Training Scholarship. LS and MEB acknowledge the financial support from Italian MIUR through Project No. PRIN 2015-HYFSRT. The authors wish to thank Dr Willem Van den Heuvel for guidance on ab initio calculations, Mr Edward Nagul for running ICP-OES and Dr Nick Chilton for helpful discussions. This research was supported by use of the NeCTAR Research Cloud, a collaborative Australian research platform supported by the National Collaborative Research Infrastructure Strategy (NCRIS).en_AU
dc.format.mediumElectronic-eCollectionen_AU
dc.identifier.citationGransbury, G. K., Boulon, M.-E., Mole, R. A., Gable, R. W., Moubaraki, B., Murray, K. S., Sorace, L., Soncini, A., & Boskovic, C. (2019). Single-ion anisotropy and exchange coupling in cobalt(ii)-radical complexes: insights from magnetic and ab initio studies. Chemical Science, 10(38), 8855-8871. doi:10.1039/C9SC00914Ken_AU
dc.identifier.issn2041-6520en_AU
dc.identifier.issn2041-6539en_AU
dc.identifier.issue38en_AU
dc.identifier.journaltitleChemical Scienceen_AU
dc.identifier.pagination8855-8871en_AU
dc.identifier.urihttps://doi.org/10.1039/c9sc00914ken_AU
dc.identifier.urihttps://apo.ansto.gov.au/handle/10238/15723en_AU
dc.identifier.volume10en_AU
dc.languageEnglishen_AU
dc.language.isoenen_AU
dc.publisherRoyal Society of Chemistryen_AU
dc.subjectAnisotropyen_AU
dc.subjectIonsen_AU
dc.subjectCobalten_AU
dc.subjectMagnetismen_AU
dc.subjectElectronic structureen_AU
dc.subjectZincen_AU
dc.subjectSpectroscopyen_AU
dc.subjectTemperature rangeen_AU
dc.titleSingle-ion anisotropy and exchange coupling in cobalt( ii )-radical complexes: insights from magnetic and ab initio studiesen_AU
dc.typeJournal Articleen_AU
dcterms.dateAccepted2019-07-27en_AU
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