Abstract

Eiza Shimizu¹ and Derrick Ethelbhert Yu^1,2

DOI : http://dx.doi.org/10.13005/ojc/340511

Partially-oxidized Iron(III) phthalocyanine (Fe^IIIPc) with axial CN or Br ligands are molecular conductors with giant negative magnetoresistance. Electron conduction occurs via intermolecular overlapping of Pc p-orbitals, while negative magnetoresistance is brought about by intramolecular interaction between Fe-d and Pc-p orbitals. Aside from permitting slip-stacked solid-state arrangement, axial ligands can further enhance the p-d interaction of Fe^III(Pc) depending on the strength of ligand field energies that proportionally leads to larger negative magnetoresistance. However, the strong ligand field of CN results in conductivity reduction due to the p-accepting nature of the ligand which enhances electron gradient in the oxidized Fe³⁺, thereby localizing itinerant electrons in Pc, as evidenced by charge transfers between Fe-d and CN-p orbitals. In contrast, the p-donating nature of Br ligands complements the electron deficiency of Fe³⁺, resulting in the delocalization of itinerant electrons in the Pc system, thus creating a highly conducting molecular system with giant negative magnetoresistance.

Axially-ligated iron(III) phthalocyanine; Giant negative magnetoresistance; molecular conductor; pi-d interaction

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