The flexibility of long chain substituents influences spin-crossover in isomorphous lipid bilayer crystals

Abstract

[Fe(bpp)2][BF4]2 (bpp = 2,6-di{pyrazol-1-yl}pyridine) derivatives bearing a bent geometry of hexadec-1-ynyl or hexadecyl substituents pyrazole are isomorphous, and high-spin at room temperature. However, only the latter compound undergoes an abrupt,...

Iron/2,6‐Di(pyrazol‐1‐yl)pyridine Complexes with a Discotic Pattern of Alkyl or Alkynyl Substituents

“…These procedures can require extended work‐ups, to separate byproducts iodinated at other sites on the bpp ligand skeleton [57] . We have found it more convenient to prepare from commercially available 4‐iodo‐1 H ‐pyrazole and 2,6‐difluoropyridine, under typical conditions employed for bpp synthesis from fluoropyridine precursors [43,58] . This gave in 68 % yield in NMR purity, without the need for additional purification.…”

“…Where mesophase behavior does not occur, SCO compounds decorated with long chains can exhibit unusual switching cooperativity in the solid state. This often reflects the involvement of conformational changes or order:disorder transitions in the alkyl substituents in the spin transition process [40–43] …”

“…To that end, we have reported [Fe(bpp) 2 ] 2+ derivatives with long alkyl chain substituents at the R 1 position and R 2 =R 3 =H; [50] and, alkyl chains at R 2 with R 1 =R 3 =H (Scheme 1). [43] These substituent patterns correspond to linear and bent amphiphile geometries, respectively. The bent amphiphilic molecules were of particular interest in forming an isomorphous series of lipid bilayer crystals, some of which exhibited an abrupt spin‐transition on cooling while others did not.…”

“…The bent amphiphilic molecules were of particular interest in forming an isomorphous series of lipid bilayer crystals, some of which exhibited an abrupt spin‐transition on cooling while others did not. These differences correlate with the length and flexibility of the R 2 alkyl chain substituents in the lattice [43] …”

Highly Ordered, Self‐Assembled Monolayers of a Spin‐Crossover Complex with In‐Plane Interactions

“…Of particular interest are highly‐ordered, self‐assembled nanostructures [2,20–22] . For example, metal complexes with long alkyl chains were shown to self‐assemble into structured multifunctional nanomaterials, [23–28] i. e ., materials in which several properties are combined, such as SCO and liquid crystal behavior [23,29–31] or magnetic exchange interactions, [32] as well as single‐molecule magnet (SMM) properties [33] . In all cases, examples have shown that the self‐assembly of such molecules to surfaces using the bottom‐up approach was a new and powerful tool to prepare devices, [34–35] which might be complementary to more traditional top‐down microfabrication techniques [34] .…”