Counterion Effect on the Spin-Transition Properties of the Cation [Fe(btzx)3]2+ (btzx=m-Xylylenebis(tetrazole))

Manuel Quesada (1) , Ferry Prins (1) , Eckhard Bill (2) , Huub Kooijman (3) , Patrick Gamez (1) , Olivier Roubeau (4) , Anthony L. Spek (3) , Jaap G. Haasnoot (1) , Jan Reedijk (1)

1 Leiden Institute of Chemistry
2 Max‐Planck‐Institut für Bioanorganische Chemie
3 Bijvoet Center of Biomolecular Research [Utrecht]
4 CRPP - Centre de recherches Paul Pascal

Abstract: The influence of the counteranion on the structure and the spintransition properties of original 1D bis(tetrazole) FeII systems, namely[Fe(btzx)3]X2 (X=PF6 (1), CF3SO3(2) and ClO4 (3); btzx=m-xylylenebis( tetrazole)) is studied. The X-ray crystal structures of compounds 1 and 2 are described in detail. These structures present a solvent molecule encapsulated within pockets formed by btzx ligands along the 1D coordination chains. Compound 2 is shown to be the first structurally characterised alternating HS–LS 1D spin-transition system (HS=high spin, LS=low spin). The magnetic susceptibility measurements of all three compounds are compared. The degree of completion and the transition temperature are both drastically influenced by the counterion used, while surprisingly, the cooperative nature of the transition is not affected by the choice of counterion. Compounds 1 and 2 are further studied by Mçssbauer spectroscopy and their dis tinct LIESSTproperties are compared.

Mots clés: spin crossover; polymers; bis(tetrazole); iron; anions

Domaines: Matériaux; Chimie de coordination

Manuel Quesada, Ferry Prins, Eckhard Bill, Huub Kooijman, Patrick Gamez, et al.. Counterion Effect on the Spin-Transition Properties of the Cation [Fe(btzx)3]2+ (btzx=m-Xylylenebis(tetrazole)). Chemistry - A European Journal, 2008, 14 (28), pp. 8486-8499. ⟨10.1002/chem.200800990⟩. ⟨hal-00323792⟩