Ionic compound containing iron phthalocyanine (FeIPc)− anions and (C70−)2 dimers. Optical and magnetic properties of (FeIPc)− in the solid state

Abstract

Ionic compounds containing the anion of iron phthalocyanine (Fe^IPc)⁻, {(Fe^IPc)⁻}·(cryptand[2,2,2]·[Na⁺])·(C₆H₄Cl₂) (1), and the fullerene C₇₀⁻ and Fe^IPc⁻ anions, (C₇₀⁻)₂·{(Fe^IPc)⁻}₆·(cryptand[2,2,2]·[Na⁺])₈·(C₆H₄Cl₂)_8.65·(C₆H₁₄)_0.35 (2), were obtained as single crystals. Their crystal structures and optical and magnetic properties were analyzed. Spectra of 1 and 2 manifest intense bands in visible-NIR range at 820, 690, 555, 528, 449, 400 and 316 nm attributed to (Fe^IPc)⁻. The four-coordinate (Fe^IPc)⁻ anions show an EPR signal with perpendicular and parallel components at g_⊥ = 2.487 and g_‖ = 2.353 in 1 and g_⊥ = 2.328 and g_‖ = 2.230 in 2. According to magnetic measurements the (Fe^IPc)⁻ anions have low spin (S = 1/2) state indicating d⁷ configuration for the Fe^I atoms with the odd electron on the d_z² orbital. Fullerene anions form singly bonded (C₇₀⁻)₂ dimers in 2, the shape of which efficiently fitted with the large planar phthalocyanine anions to be surrounded completely by eight (Fe^IPc)⁻ anions. The (C₇₀⁻)₂ dimers are diamagnetic and EPR silent up to 350 K. Both complexes contain channels formed by four (Fe^IPc)⁻ planes in 1 or four (Fe^IPc)⁻ planes and two (C₇₀⁻)₂ dimers in 2. The channels are occupied by double chains of alternating cryptand[2,2,2]·[Na⁺] cations and solvent C₆H₄Cl₂ molecules.