A Trinuclear Iron(III) Complex of a Triple Noninnocent Ligand for Spin-Structured Molecular Conductors.

Abstract

N,N',N'',N''',N'''',N'''''-(Triphenylene-2,3,6,7,10,11-hexayl)hexapicolinamide (H6 hptp), a triangular ligand containing three noninnocent coordination sites, and its trinuclear iron(III) complex (PPh4 )3 [FeIII 3 (hptp)6 (CN)6 ] were prepared. In this complex, three low-spin Fe3+ ions are coordinated by the triangular hptp6- bridging ligand at its apices. Cyclic voltammetry of (PPh4 )3 [FeIII 3 (hptp)6 (CN)6 ] in PhCN solution showed one reductive wave for 3 Fe2+ /3 Fe3+ and three oxidative waves for the hptp6- ligand. The controlled-potential electronic spectra of the solution presented broad absorption bands in the near-IR (NIR) region for oxidations because a π-radical is generated on the hptp6- ligand. The EPR spectra of frozen solutions also showed large oxidization-state dependent differences caused by the strong exchange interactions between the electrons in the d orbitals of the Fe3+ ions and those of the π-radicals in the hptp6- ligand. The electronic and magnetic states of the oxidized species were investigated using density functional theory.