SPIN CROSSOVER PROPERTIES OF IRON(II) COMPLEXES WITH A N_4O_2 DONOR SET BY EXTENDED Ⅱ-CONJUGATED SCHIFF-BASE LIGANDS

摘要

The preparation and magnetic properties of three Fe(II) Schiff-base complexes, [Fe(qnal-21)_2]?CH_2Cl_2 (1), [Fe(qnal-12)_2]?2C_6H_6 (2) and [Fe(Hqsalc)_2] (3), (Hqnal-21 = N-(8'-quinolyl)-2-hydroxy-1-naphthaldimine, Hqnal-12 = N-(8'-quinolyl)-1-hydroxy-2-naphthaldimine, H2qsalc = 4-hydroxy-3-[(8-quinolinylimino)methyl]benzoic acid) are reported. X-ray single crystal structure analyses of 1 and 2 reveal that an Fe(II) ion in each complex is coordinated by two Schiff-base ligands, qnal-21 or qnal-12, in a meridional fashion. Molecular packing of 2 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 2 shows a high-spin state at all the temperature range measured, the χT-T plot of 3 shows abrupt spin crossover behavior with a wide hysteresis of 21 K, probably due to the hydrogen-bond network originated by carboxyl groups.