Effects of weak interactions on spin crossover properties of iron(II) complexes with extended π-conjugated Schiff-base ligands

Abstract

The preparation and magnetic properties of two Fe(II) Schiff-base complexes, [Fe(qnal-12) 2]·2C 6H 6 ( 1) and [Fe(Hqsalc) 2] ( 2), (Hqnal-12 = N-(8′-quinolyl)-1-hydroxy-2-naphthaldimine, H 2qsalc = 4-hydroxy-3-[(8-quinolinylimino)methyl]benzoic acid) are reported. X-ray single crystal structure analysis of 1 reveals that an Fe(II) ion is coordinated by two qnal-12 ligands in a meridional fashion. Molecular packing of 1 shows that a qnal-12 interacts with neighboring two qnal-12’s through π–π interactions, which results in the formation of one-dimensional chain. Although the magnetic property of 1 shows a high-spin state at all the temperature range measured, the χT– T plot of 2 shows abrupt spin crossover behavior with a wide hysteresis of 21 K, probably due to the hydrogen-bond network originated by carboxyl groups.