Amphiphilic iron(ii) complexes with short alkyl chains – crystal packing and spin transition properties

Abstract

An amphiphilic iron(II) spin crossover complex with relatively short octyl chains was synthesised and the crystal structures of the high spin and the low spin state could be determined. In further reactions, a second modification of the hexa-coordinated complex and two different penta-coordinated complexes could be obtained and characterised by X-ray structure analysis. The examples demonstrate an influence of the alkyl chains on the stoichiometry of the final product. Different arrangements of the alkyl chains were observed in the crystal packing. Despite those differences, the spin transition of the hexacoordinated complexes is always gradual and comparable to that observed in solution.

Iron(ii) spin crossover complexes with diaminonaphthalene-based Schiff base-like ligands: mononuclear complexes

“…24,25 Measured O eq -Fe-O eq angles for the HS structures (106.98(14)°for 10 HS , 111.5(4)°, and 112.6(4)°for 11) and for the LS structures (90.49(12)°for 10 LS and 87.79(14)°for 12) are in agreement with similar compounds in literature. 8,26 Selected bond lengths and angles are listed in Table 4. Upon SCO, the volume of the cell of 10 is reduced by 2.5%, in agreement with the volume reduction of the coordination sphere of the iron centre as it switches from HS to LS state.…”

Solution and Solid‐State Study of the Spin‐Crossover [FeII(R‐bik)3](BF4)2 Complexes (R = Me, Et, Vinyl)

“…In fact, the NMR spectroscopic chemical shifts are highly sensitive to changes in electronic ground states in transition‐metal complexes . Alternatively, magnetic measurements of solutions can be used to follow the temperature dependence of the magnetic susceptibility in a direct manner . However, this method is not so common and it may suffer from approximations; for example, due to an important diamagnetic contribution (arising from the dilution of the paramagnetic species in a diamagnetic solvent).…”

Influence of the Alkyl Chain Length on the Self‐Assembly of Amphiphilic Iron Complexes: An Analysis of X‐ray Structures

“…Therefore, we designed N 2 O 2 -coordinating Schiff-base-like equatorial ligands with long alkyl chains in the outer periphery (Scheme 1). In combination with various axial ligands, octahedral iron(II) complexes with thermal spin crossover activity can be realised, [16][17][18] and the influence of the hydrophobic substituents can be investigated. In a previous work we showed, that the amphiphilic complexes of this family can self-assemble to lipid-layer-like arrangements, [16,17] with one of those complexes exhibiting a highly cooperative spin transition with a wide hysteresis loop.…”