Iron(II) Complexes Having Dinuclear Mesocate or Octanuclear Bicapped Trigonal Prism Structures Dependent on the Rigidity of Bis(bidentate) Schiff Base Ligands Containing Imidazole Groups

Dinuclear complex, [Fe2(H2L1,Me)3](ClO4)4 (1Me, H2L1,Me = N,N'-(1,3-phenylene)bis(1-(5-methyl-1H-imidazol-4-yl)methanimine)), and octanuclear complexes, [Fe8(H2L2,H)12](ClO4)16 (2HClO4: H2L2,H = N,N'-(1,3-phenylenebis(methylene))bis- (1-(1H-imidazol-4-yl)methanimine) and [Fe8(H2L2,Me)12](X)16 (2MeX: H2L2,Me = N,N'-(1,3-phenylenebis(methylene))bis- (1-(5-methyl-1H-imidazol-4-yl)methanimine), X = ClO4, BF4), were synthesized. It was revealed by X-ray analysis that 1Me has a dinuclear mesocate structure. On the other hand, 2HClO4 and 2MeX have novel octanuclear bicapped trigonal prism structures with six iron(II) sites having the meridional configuration on vertexes and two iron(II) sites having the facial one on the centers of each triangular base. Magnetic susceptibility studies indicated that these dinuclear and octanuclear complexes show gradual spin-crossover (SCO) behavior.