BCSJ : Vol. 78 (2005) , No. 7 pp.1279-1282

Infinite Chain Structure and Steep Spin Crossover of a Fe^III Complex with a N₃O₂ Pentadentate Schiff-Base Ligand and 4-Aminopyridine

Kyoichi Tanimura¹⁾, Ryoko Kitashima¹⁾, Nicolas Bréfuel¹⁾, Masaaki Nakamura¹⁾, Naohide Matsumoto¹⁾, Sergiu Shova²⁾ and Jean-Pierre Tuchagues²⁾

1) Department of Chemistry, Faculty of Science, Kumamoto University
2) Laboratoire de Chimie de Coordination du CNRS

(Received January 7, 2005)

A spin crossover (SC) Fe^III complex, [Fe^III(4-NH₂py)L]BPh₄, was synthesized and characterized, where 4-NH₂py = 4-aminopyridine, H₂L = pentadentate N₃O₂ Schiff-base ligand of the 2:1 condensation product of 3-methoxysalicylaldehyde and bis(3-aminopropyl)methylamine, and BPh₄⁻ = tetraphenylborate. Cryomagnetic susceptibility measurements revealed a steep spin transition between Fe^III low-spin (S = 1/2) and high-spin (S = 5/2) states at T_1/2 = 120 K, but showed no hysteresis. Crystal-structural analyses were performed at 293 and 90 K in order to investigate the origin of the steep spin crossover, and to determine the structures of the high-spin and low-spin states. The crystal structure consisted of a one-dimensional chain constructed by hydrogen bonds between the amino group of 4-NH₂py of a molecule and the methoxy group of the adjacent molecule.