Spin-crossover compounds based on iron(II) complexes of 2,6-bis(pyrazol-1-yl)pyridine (bpp) functionalized with carboxylic acid and ethyl carboxylic acid

Víctor García-López (1) , Mario Palacios-Corella (1) , Alexandre Abhervé (1) , Isaac Pellicer-Carreño (1) , Cédric Desplanches (2) , Miguel Clemente-León (1) , Eugenio Coronado (1)

1 ICMol - Instituto de Ciencia Molecular
2 ICMCB - Institut de Chimie de la Matière Condensée de Bordeaux

Four new salts of the iron(II) complex of the 2,6-bis(pyrazol-1-yl)pyridine ligand functionalized with a carboxylic acid group (bppCOOH) of formulas [Fe(bppCOOH)2](BF4)2 (1(BF4)2), [Fe(bppCOOH)2](CF3SO3)2·yMe2CO (1(CF3SO3)2·yMe2CO), [Fe(bppCOOH)2](AsF6)2·yMe2CO (1(AsF6)2·yMe2CO) and [Fe(bppCOOH)2](SbF6)2·yMe2CO (1(SbF6)2·yMe2CO) have been prepared and characterized together with a more complete structural and photomagnetic characterization of the previously reported [Fe(bppCOOH)2](ClO4)2 (1(ClO4)2). Furthermore, the iron(II) complex of the ethyl ester derivative of bppCOOH (bppCOOEt) has been prepared and characterized (compound [Fe(bppCOOEt)2](ClO4)2·yMe2CO, 2(ClO4)2·yMe2CO). Isostructural 1(BF4)2 and 1(ClO4)2 show an abrupt and reversible spin transition with a much lower T1/2 for the BF4− salt. CF3SO3−, SbF6− and AsF6− counteranions and the bppCOOEt ligand lead to the incorporation of solvent molecules in the structures, which play an important role in the spin-crossover properties of these compounds. In the case of 1(CF3SO3)2·yMe2CO, a reversible spin transition is obtained after desolvation. All these compounds show a LIESST effect.

Domaines: Matériaux

Víctor García-López, Mario Palacios-Corella, Alexandre Abhervé, Isaac Pellicer-Carreño, Cédric Desplanches, et al.. Spin-crossover compounds based on iron(II) complexes of 2,6-bis(pyrazol-1-yl)pyridine (bpp) functionalized with carboxylic acid and ethyl carboxylic acid. Dalton Transactions, 2018, 47 (47), pp.16958-16968. ⟨10.1039/C8DT03511C⟩. ⟨hal-01945584⟩