Variety of spin transition temperatures of iron(II) spin crossover complexes with halogen substituted Schiff-base ligands, HqsalX (X = F, Cl, Br, and I)

Abstract

The preparation and magnetic properties of four Fe(II) Schiff-base complexes, [Fe(qsalX)2] (HqsalX=N-(8′-quinolyl)-2-hydroxy-5-halogeno-1-salicylaldimine; X=F(1), Cl(2), Br(3), I(4)) are reported. X-ray single crystal structure analyses of 1 and 2 reveal that Fe(II) ions in both complexes are coordinated by two qsalX ligands in meridional fashion. Molecular packing of 1 shows that a non-planar qsalF ligand interacts with neighboring two qsalF ligand’s through π–π interactions, while that of 2 shows that two planar qsalCl ligands interact each other through π–π interaction. Although the magnetic property of 1 shows a high-spin state at all the temperature range measured, the χT–T plots of 2, 3, and 4 show gradual spin crossover behaviors with T1/2 of 308K, 341K, and 340K, respectively.