Ln = Gd (11a), Dy (11b), Tb (11c), Ho (11d), Er (11e) 12 Ln = Dy (12a), Tb (12b), Ho (12c), Er (12d), Lu (12e) 13 Scheme 1-1 Synthetic routes to sulfur diimides. The first reaction was performed with SCl 4 and n-butylamine (1). The reaction of the more stable SCl 2 and tert-butylamine (2) initially resulted in a polymer that undergoes a slow pyrolysis under elevated temperatures (3). [33] It comprises the oxidation of [Li 4 {(NtBu) 3 S} 2 ] [31] (SN-II) with Br 2 , which resulted in easily

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... ollable synthesis parameters and higher yields. Interestingly, an intense blue intermediate radical species forms at the beginning of the reaction, which was subsequently characterized by EPR spectroscopy. [31, 33] 36] [37] The compound consists of a dysprosium metallocene cation [(Cp iPr5 )Dy(Cp*)] + (Cp iPr5 = penta-isopropyl-cyclopentadienyl; Cp* = pentamethylcyclopentadienyl) and a [B(C 6 F 5 ) 4 ]counterion and it displays a remarkable hysteresis even above the boiling point of liquid nitrogen, i.e. up to 80 K . However, it seems possible that the structural optimization for this ligand class has reached a highlevel plateau and that new approaches with rather underexplored compounds should come into focus to further develop the field of molecular magnetism. M S states, E determines the mixing of different states with ΔM S =±2, which induces transverse anisotropy, an obstacle for SMM behavior. A good SMM should have a large, negative D value (maximum M S is stabilized) and a negligible amount of E. In contrast, a stabilization of the lowest M S state would result in a positive D value (Figure 1 -5, right). However, in systems with first-order angular momentum and strong SOC, D and E are no longer valid for a proper description. Therefore, the quantum number S, which only takes the spin into account, needs to be replaced by the quantum number J, a combination of the spin and the OAM (J = |S ± L|). [126] Here, the effective energy barrier U eff (experimentally measured value) can be lower or equal compared to U (energy between the highest and lowest M S state). For example, in a d 7 spin system with M S = 3/2 a transition is only possible between M S = ±3/2 and ±1/2, hence U and U eff are equal (Figure 1 -5, right). For f-elements, both values are often different, since more than two Kramers' doublets offer the possibility for a transition through excited states. A Raman process works in the same manner, but it includes the transition into a virtual state. [171] other important process is the temperature-independent quantum tunneling of the magnetization