Modelling the Magnetic Behaviour of Square‐Pyramidal CoII5 Aggregates: Tuning SMM Behaviour through Variations in the Ligand Shell |
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| Authors: | Frederik Klöwer Yanhua Lan Dr. Joscha Nehrkorn Oliver Waldmann Prof. Christopher E. Anson Dr. Annie K. Powell Prof. |
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| Affiliation: | 1. Institut für Anorganische Chemie der Universit?t Karlsruhe, Karlsruhe Institute of Technology, Engesserstrasse 15, 76131 Karlsruhe (Germany), Fax: (+49)?721‐608‐8142;2. Physikalisches Institut, Universit?t Freiburg, Hermann‐Herder‐Strasse 3, 79104 Freiburg (Germany) |
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| Abstract: | Three new μ4‐bridged CoII5 clusters with similar core motifs have been synthesised with the use of N‐tert‐butyldiethanolamine (tbdeaH2) and pivalic acid (piv): [CoII5(μ4‐N3)(tbdea)2(μ‐piv)4(piv)(CH3CN)2]?CH3CN ( 1 ), [CoII5(μ4‐Cl)(Cl)(tbdea)2(μ‐piv)4(pivH)2] ( 2 ) and [CoII5(μ4‐N3)(Cl)(tbdea)2(μ‐piv)4(pivH)2] ( 3 ). Magnetic measurements were performed for all three compounds. It was found that while the chloride‐bridged cluster 2 does not show an out‐of‐phase signal, which excludes single‐molecule magnet (SMM) behaviour, the azide‐bridged compounds 1 and 3 show out‐of‐phase signals as well as frequency dependence of the ac susceptibility, as expected for SMMs. We confirmed that 1 is a SMM with zero‐field quantum tunnelling of the magnetisation at 1.8 K. Compound 3 is likely a SMM with a blocking temperature well below 1.8 K. We established a physical model to fit the χT versus T and M versus B curves of the three compounds to reproduce the observed SMM trend. The analysis showed that small changes in the ligand shell modify not only the magnitude of exchange constants, but also affect the J and g matrices in a non‐trivial way. |
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| Keywords: | cluster compounds cobalt magnetic properties molecular modeling single‐molecule studies single‐molecule magnets |
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