Abstract
Understanding how the magnetic anisotropy in simple coordination complexes can be manipulated is instrumental to the development of single-molecule magnets (SMMs). Clear strategies can then be designed to control both the axial and transverse contributions to the magnetic anisotropy in such compounds, and allow them to reach their full potential. Here we show a strategy for boosting the magnetic anisotropy in a series of trigonal bipyramidal Mn(ii) complexes - [MnCl3(HDABCO)(DABCO)] (1), [MnCl3(MDABCO)2]·[ClO4] (2), and [MnCl3(H2O)(MDABCO)] (3). These have been successfully synthesised using the monodentate [DABCO] and [MDABCO]+ ligands. Through static (DC) magnetic measurements and detailed theoretical investigation using ab initio methods, the magnetic anisotropy of each system has been studied. The calculations reveal that the rhombic zero-field splitting (ZFS) term (E) can be tuned as the symmetry around the Mn(ii) ion is changed. Furthermore, an in silico investigation reveals a strategy to increase the axial ZFS parameter (D) of trigonal bipyramidal Mn(ii) by an order of magnitude.
Highlights
Magnetic anisotropy gives rise to a preference for the magnetisation to be pinned in one of two orientations for an easy-axis type system.[1]
Magnetic anisotropy in particular transpires due to zero-field splitting (ZFS) which removes the degeneracy of Ms states in zero-field for axially symmetric molecules where S > 1/2 through the effects of spin–orbit coupling (SOC).[1]
Crystal structure descriptions Complex 1 crystallises in the trigonal R32 space group with the corresponding crystallographic data given in Table S1.† The complex has two DABCO moieties coordinated in the axial positions of a central MnII, each through a single N donor and with 3 symmetry related Cl sites occupying the equatorial positions completing the trigonal bipyramidal (TBP) coordination geometry
Summary
Magnetic anisotropy gives rise to a preference for the magnetisation to be pinned in one of two orientations for an easy-axis type system.[1]. To a solution of MnCl2·4H2O (0.40 g, 2 mmol) in 10 ml of methanol, a colourless solution of DABCO (0.22 g, 2 mmol) in methanol (10 ml) was added, resulting in a yellow solution This solution was stirred at 60 °C for three hours after which a light brown suspension was obtained which on filtering, once cooled to room temperature, yielded a light brown precipitate and dark brown solution. To a solution of MnCl2 (0.13 g, 1 mmol) in methanol (10 ml), a colourless solution of [MDABCO][I] (0.52 g, 2 mmol) and NaClO4 (0.12 g, 1 mmol) in methanol (10 ml) was added, resulting in a pale brown solution This solution was stirred for three hours at 60 °C before cooling to room temperature. EA analysis: (C7H17MnN2Cl3O) [%], found: C 27.45, H 5.51, N 8.98; calc: C 27.43, H 5.59, N 9.14
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