A giant negative magnetoresistance effect in an iron tetrabenzoporphyrin complex. Issue 42 (1st August 2016)

• Record Type: Journal Article
• Authors: Nishi, Miki; Ikeda, Mitsuo; Kanda, Akinori; Hanasaki, Noriaki; Hoshino, Norihisa; Akutagawa, Tomoyuki; Matsuda, Masaki
• Is Part Of: Dalton transactions. Volume 45:Issue 42(2016)
• Page Start: 16604
• Page End: 16609
• Publication Date: 2016-08-01
• Subjects: Chemistry, Inorganic -- Periodicals; Chemistry, Physical and theoretical -- Periodicals; Chemistry, Inorganic -- Periodicals; 546.05
• DOI: 10.1039/c6dt01911k
• Languages: English
• ISSNs: 1477-9226

Abstract

Abstract : By measuring the electrical resistivity in TPP[Fe III (tbp)(CN)2 ]2 (TPP = tetraphenylphosphonium and tbp = tetrabenzoporphyrin) under the application of a static magnetic field, a giant negative magnetoresistance (MR) effect with high anisotropy is observed. Abstract : By measuring the electrical resistivity in TPP[Fe III (tbp)(CN)2 ]2 (TPP = tetraphenylphosphonium and tbp = tetrabenzoporphyrin) under the application of a static magnetic field, a giant negative magnetoresistance (MR) effect with high anisotropy is observed. More specifically, the MR ratio at 13 K under a field of 9 T perpendicular to the c axis is −70%, whereas the MR ratio under a field parallel to the c axis is −40%. Furthermore, electron spin resonance (ESR) measurements indicate large anisotropy in the principal g -values of d spin ( S = 1/2) in the [Fe III (tbp)(CN)2 ] unit; the g 1 value almost perpendicular to the tbp plane and the g 2 and g 3 values almost parallel to the tbp plane are 3.60, 1.24, and 0.39, respectively. It is revealed that the anisotropy in the MR effect arises from the anisotropy in the d spin, suggesting that the d spins in TPP[Fe III (tbp)(CN)2 ]2 affect the π-conduction electron via the intramolecular π–d interaction. The anisotropy and magnitude in the giant negative MR effect for TPP[Fe III (tbp)(CN)2 ]2 are smaller than the corresponding values for the isostructural phthalocyanine (Pc) analogue TPP[Fe III (Pc)(CN)2 ]2 . This is consistent with the fact that the intermolecular antiferromagnetic d–d interaction in TPP[Fe III (tbp)(CN)2 ]2 (suggested by the Weiss temperature: Θ = −8.0 K) is weaker than that in TPP[Fe III (Pc)(CN)2 ]2 ( Θ = −12.3 K). This indicates that the minor modification in coordination complexes can significantly affect the MR effect via tuning the intermolecular d–d interaction as well as the intermolecular π–π overlap.