Chemistry - A European Journal · 2019 · 27 citations · 51 references
The single-molecule magnet (SMM) properties of a series of ferrocenium complexes, [Fe(η<sup>5</sup> -C<sub>5</sub> R<sub>5</sub> )<sub>2</sub> ]<sup>+</sup> (R=Me, Bn), are reported. In the presence of an applied dc field, the slow dynamics of the magnetization in [Fe(η<sup>5</sup> -C<sub>5</sub> Me<sub>5</sub> )<sub>2</sub> ]BAr<sub>F</sub> are revealed. Multireference quantum mechanical calculations show a large energy difference between the ground and first excited states, excluding the commonly invoked, thermally activated (Orbach-like) mechanism of relaxation. In contrast, a detailed analysis of the relaxation time highlights that both direct and Raman processes are responsible for the SMM properties. Similarly, the bulky ferrocenium complexes, [Fe(η<sup>5</sup> -C<sub>5</sub> Bn<sub>5</sub> )<sub>2</sub> ]BF<sub>4</sub> and [Fe(η<sup>5</sup> -C<sub>5</sub> Bn<sub>5</sub> )<sub>2</sub> ]PF<sub>6</sub> , also exhibit magnetization slow dynamics, however an additional relaxation process is clearly detected for these analogous systems.
51