A spin-crossover complex based on a 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) ligand functionalized with a carboxylate group

Abstract

Combining Fe(ii) with the carboxylate-functionalized 2,6-bis(pyrazol-1-yl)pyridine (bppCOOH) ligand results in the spin-crossover compound [Fe(bppCOOH)2](ClO4)2 which shows an abrupt spin transition with a T1/2 of ca. 380 K and a TLIESST of 60 K due to the presence of a hydrogen-bonded linear network of complexes.

Fe(II) spin crossover complexes of a derivative of 2,6-bis(pyrazol-1-yl)pyridine (1-bpp) functionalized with a carboxylic acid in the 3-pyridyl position

“…In previous works, we prepared the Fe(II) complex of bpp ligand functionalized with a carboxylic acid at the 4-pyridyl position (2,6-di(pyrazol-1-yl)-pyridine-4-dicarboxylic acid, bppCOOH, see Scheme 1). We showed that the solvent-free ClO 4 and BF 4 salts of [Fe II (bppCOOH) 2 ] 2+ exhibit abrupt thermal and light-induced spin transition related to the presence of a hydrogen-bonded linear network of complexes, whereas the incorporation of solvent molecules in the structure of the CF 3 SO 3 -, AsF 6 an SbF 6 salts induces reversible solvent-induced SCO [5][6]. The carboxylic acid of these SCO complexes could be used for the preparation of polynuclear metal complexes [7].…”

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

“…In a previous work, we prepared the iron(II) complex of bpp ligand functionalized with a carboxylic acid (bppCOOH, see Scheme 1). 5 This resulted in the SCO compound [Fe(bppCOOH) 2 ](ClO 4 ) 2 , which forms an extended 1D network built via hydrogen-bond intermolecular interactions. This leads to an abrupt spin transition with T 1/2 (T 1/2 = temperature of 50 % HS→LS conversion) of ca.…”

Bimetallic MnIII–FeII hybrid complexes formed by a functionalized MnIII Anderson polyoxometalate coordinated to FeII: observation of a field-induced slow relaxation of magnetization in the MnIII centres and a photoinduced spin-crossover in the FeII centres

“…Indeed, minimum distances between Fe and Mn are close to 6.4 Å in 2. Finally, as spin-crossover of other 1-bpp derivatives has been observed at temperatures well above 300 K, 34 w m T of 3 has been measured up to 400 K. Unfortunately, w m T remains close to LS values indicating that no spin-crossover is taking place in this polymer. To see if it was possible to photoinduce the spin-crossover, 3 was irradiated with green light (l = 532 nm, optical power 3.4 mW cm À2 ) at 10 K. A small but significant increase of the magnetic signal was observed.…”