Effects of Metal Doping on the Spin-Crossover Properties of an Iron(II) Complex with Extended π-Conjugated Schiff-Base Ligand Having an N4O2 Donor Set

Abstract

Abstract The spin-crossover (SCO) complex [Fe(qnal)2]·CH2Cl2 (1), (Hqnal: N-(8′-quinolyl)-2-hydroxy-1-naphthaldimine) with an N4O2 donor set, has been synthesized and characterized. Investigation of magnetic properties shows that the complex exhibits an abrupt and complete spin transition with a 5 K wide thermal hysteresis loop. The X-ray diffraction analysis of complex 1 reveals that the molecules are connected into a quasi one-dimensional chain through extended π–π interactions between aromatic rings of ligands. The effects of metal doping on SCO properties have been investigated in the mixed-metal system [Fe1−xMx(qnal)2]·CH2Cl2 (M = zinc(II) and nickel(II)). The results reveal that metal doping increases the gradual character of spin transition, and no marked differences found between zinc and nickel doping, which suggest the dominant effect of the doping-degree (concentration) rather than metal species on cooperativity. However, the metal doping shows different effects on critical temperature (T1/2), where a more pronounced descending of T1/2 is observed in response to increased Zn-doping than in Ni-doping, indicating the noticeable consequence of internal pressure due to the different radii of doping metal ions.