The Paramagnetic or Spin Crossover Iron(III) Complexes Based-on Pentadentate Schiff Base Ligand: Crystal Structure, and Magnetic Property Investigation

Abstract

A series of bi- or mononuclear hexacoordinate iron(III) complexes, [Fe(L)][Fe(bpb)(CN)2]·CH3OH·0.5H2O (1), [Fe(L)][Co(bpb)(CN)2]·CH3OH (2) [(Fe (L))2(4,4’-bipy)](BPh4)2 (3), [Fe(L)(py)](BPh4) (4) and [Fe(L)(dmap)](BPh4) (5) (bpb = 1,2-bis(pyridine-2-carboxamido)benzenate, L = N,N’-bis(2-hydroxybenzyliden)-1,7-diamino-4-azaheptane, dmap = 4-dimethylaminopyridine), have been prepared with the pentadentate Schiff base iron(III) compound as assemble precursor and characterized by element analysis, IR and X-ray diffraction. Single crystal structural determination revealed the neutral cyanide-bridged binuclear entity for complexes 1 and 2 and the cationic di- or mononuclear structure for complexes 3–5 with the positive charge(s) balanced by BPh4– ion(s). The experimental study and theoretical simulation of the magnetic property discovered the ferromagnetic coupling between the Fe(III) ions bridged by cyanide group in complex 1 and the always high spin state of the Fe(III) ion coordinated to the Schiff base ligand in both complexes 1 and 2. The temperature dependent magnetic susceptibility investigation over complexes 3–5 showed the occurrence of the thermo-induced gradual complete spin crossover (SCO) property at about 115, 170 and 200 K, respectively.

Keywords

• cyanide-bridged
• ferromagneitic coupling
• spin crossover
• dft calculation