X-ray near-edge absorption study of temperature-induced low-spin-to-high-spin change in metallo-supramolecular assemblies

Bahia Arezki; Guntram Schwarz; Yves Bodenthin; Dirk Luetzenkirchen-Hecht; Christian Markert; Ralph Wagner; Ronald Frahm; Dirk G Kurth; Ullrich Pietsch

doi:10.1002/cphc.201000428

X-ray near-edge absorption study of temperature-induced low-spin-to-high-spin change in metallo-supramolecular assemblies

Chemphyschem. 2011 Feb 7;12(2):405-10. doi: 10.1002/cphc.201000428. Epub 2010 Dec 22.

Authors

Bahia Arezki¹, Guntram Schwarz, Yves Bodenthin, Dirk Luetzenkirchen-Hecht, Christian Markert, Ralph Wagner, Ronald Frahm, Dirk G Kurth, Ullrich Pietsch

Affiliation

¹ Physics Department, Universtiy of Siegen, Walter-Flex Str. 3, 57072 Siegen, Germany. bahia.arezki@uni-siegen.de

PMID: 21275032
DOI: 10.1002/cphc.201000428

Abstract

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 FeN(6) 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 FeN(6) 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.