X-Ray Near-Edge Absorption Study of Temperature-Induced Low-Spin-to-High-Spin Change in Metallo-Supramolecular Assemblies

• Published in: Chemphyschem 2011-02, Vol.12 (2), p.405-410
• Main Authors: Arezki, Bahia, Schwarz, Guntram, Bodenthin, Yves, Luetzenkirchen-Hecht, Dirk, Markert, Christian, Wagner, Ralph, Frahm, Ronald, Kurth, Dirk G., Pietsch, Ullrich
• Format: Article
• Language: English
• Subjects: Applied sciences; bis-terpyridine ligands; Exact sciences and technology; Inorganic and organomineral polymers; iron(II) complexes; molecular magnetism; Physicochemistry of polymers; Properties and characterization; spin crossover; X-ray absorption spectroscopy
• ISSN: 1439-4235; 1439-7641
• DOI: 10.1002/cphc.201000428

X‐ray absorption near the iron K edge (XANES) was used to investigate the characteristics of temperature‐induced low‐spin‐to‐high‐spin change (SC) in metallo‐supramolecular polyelectrolyte amphiphile complexes (PAC) containing FeN6 octahedra attached to two or six amphiphilic molecules. Compared to the typical spin‐crossover material Fe(phen)2(NCS)2 XANES spectra of PAC show fingerprint features restricted to the near‐edge region which mainly measures multiple scattering (MS) events. The changes of the XANES profiles during SC are thus attributed to the structure changes due to different MS path lengths. Our results can be interpreted by a uniaxial deformation of FeN6 octahedra in PAC. This is in agreement with the prediction that SC is originated by a structural phase transition in the amphiphilic matrix of PAC, but in contrast to Fe(phen)2(NCS)2, showing the typical spin crossover being associated with shortening of all the metal–ligand distances. Spin doctor: X‐ray absorption near the iron K edge is used to investigate the characteristics of temperature‐induced low‐spin‐to‐high‐spin change (SC) in metallo‐supramolecular polyelectrolyte amphiphile complexes (PAC) containing FeN6 octahedra attached to two or six amphiphilic molecules (see picture). A uniaxial deformation of the FeN6 octahedron in PAC that accompanies the structural phase transition previously predicted as being responsible of the thermally induced change from the LS to the HS state is observed.