Magnetic and spectroscopic investigations of tetra-(4-t-butyl)phthalocyano complexes of μ-oxo-bridged iron(II) dimer

Abstract

The tetra(4-t-butyl)phthalocyanine derivative of the μ-oxo dimer of Fe was studied by ESR and Mössbauer spectroscopic and magnetic susceptibility methods. The Mössbauer spectrum of the iron complex shows ΔE_Q = 1.34 mm s^-1 and δ = 0.14 mm s-1. The susceptibility data measured as a function of temperature fit the S₁ = S₂ = 1 dimer with J = -5.2 cm^-1 and thus the oxidation state of iron is suggested as +2. The weak exchange coupling is attributed to the presence of the bulky t-butyl groups on phthalocyanine. It is proposed that the two phthalocyanine moieties are not superimposable on one another owing to the steric hindrance posed by the t-butyl groups of Pc^t. This is likely to lead to a rotation of one of the FePc^t moieties about the Fe-O-Fe axis as well as an increase in Fe-O distance.