The Halogen Effect on the Magnetic Behaviour of Dimethylformamide Solvates in [Fe(halide-salEen)2]BPh4

Abstract

Complexes [Fe(X-salEen)2]BPh4·DMF, with X = Br (1), Cl (2), and F (3), were crystallised from N-ethylethylenediamine with the aim of understanding the role of a high boiling point N,N′-dimethylformamide solvate in the spin crossover phenomenon. The counter ion was chosen for only being able to participate in weak intermolecular interactions. The compounds were structurally characterised by single crystal X-ray diffraction. Complex 1 crystallised in the orthorhombic space group P212121, and complexes 2 and 3 in the monoclinic space group P21/n. Even at room temperature, low spin was the predominant form, although complex 2 exhibited the largest proportion of the high-spin species according to both the magnetisation measurements and the Mössbauer spectra. Density Functional Theory calculations were performed both on the periodic solids and on molecular models for complexes 1–3 and the iodide analogue 4. While all approaches reproduced the experimental structures very well, the energy balance between the high-spin and low-spin forms was harder to reproduce, though some calculations pointed to the easier spin crossover of complex 2, as observed. Periodic calculations with the functional PBE led to very similar ΔEHS-LS values for all complexes but showed a preference for the low-spin form. However, the single-point calculations with B3LYP* showed, for the model without solvate, that the Cl complex should undergo spin crossover more easily. The molecular calculations also reflected this fact, which was more clearly defined when the cation–anion–solvate model was used. In the other models there was not much difference between the Cl, Br, and I complexes.

Reversible Single-Crystal-to-Single-Crystal Transformations in a salEen Fe(III) Spin Crossover Sponge

“…The bond lengths around the iron­(III) center, with values of Fe–O (1.876(9) and 1.897(8) Å), Fe–N (amine) (2.119(10) and 2.106(10) Å), and Fe–N (imine) (1.980(9) and 1.990(10) Å) match the magnetic data at room temperature, where a mixture of LS/HS with predominance of the LS is expected. While the Fe–O and the Fe–N (imine) match the bond lengths expected for a LS state, the Fe–N (amine) bond lengths are neither LS nor HS. − Powder X-ray data collected at room temperature on a pristine sample of 1 shows that the single crystal is a good representation of the bulk, Figure S7.…”

Synthesis, characterization and magnetic properties of halogenated tetranuclear cubane-like nickel(ii) complexes

“…30–32 However, recently many different directions have been pursued in the research field of SMMs, 33–45 in which an important direction is to explore the effects of ligand substitution. 10,46…”

The role of intermolecular interactions in [Fe(X-salEen)2]ClO4 spin crossover complexes

“…[31][32][33][34][35][36] We previously reported the halide (Cl, Br, I) derivatives of [Fe(3,5-halide-salEen) 2 ]X (X = ClO 4 − , BPh 4 − ) and tried to understand the origin of their interesting and unusual magnetic profiles. 34,35,[37][38][39][40] For ClO 4 − salts, the bromine derivative was obtained in two polymorphic forms each with very distinct magnetic profiles, one exhibiting the thermosalient effect while changing the spin state and the other displaying abrupt spin transition at 172 K. The iodine derivative, in turn, behaved very similarly to one of the polymorphic forms of the bromine derivative and also displayed the thermosalient effect while changing the spin state. However, this behaviour was only found in the first heating/cooling cycle and after this, the magnetic profile of the compound was only gradual and matched the profile obtained for the cooling routine.…”