A tetrairon(III) single-molecule magnet and its solvatomorphs: synthesis, crystal structures and vapor-phase processing

With the aim of investigating the impact of lattice solvent on the processability of tetrairon(III) single-molecule magnets by thermal sublimation, two new solvatomorphs of [Fe4(LPh)2(dpm)6] (1) were prepared and structurally characterized along with unsolvated 1 (H3LPh = 2-(hydroxymethyl)-2-phenylpropane-1,3-diol, Hdpm = dipivaloylmethane). All solvatomorphs crystallize in the C2/c space-group whereas solvent-free 1 belongs to a different space group (P21/c). The pitch of the propeller-like tetrairon(III) molecules is distinctly different in solvated vs. unsolvated phases, highlighting the effect of intermolecular interactions and crystal packing. The compounds sublimate at 450 - 490 K (in high vacuum conditions ~ 10^-6-10^-7 mbar) affording thick deposits which display different crystallinity depending on the particular starting material used. However, all sublimated samples retain slow magnetic relaxation with thermal activation parameters comparable to those of microcrystalline 1. The results indicate that factors other than mere molecular structure have a limited influence on the processability of these materials by thermal sublimation.