An iron(iii)-centred ferric wheel Fe⊂{Fe₆} with a siloxane-based bis-salicylidene Schiff base

A new iron(iii)-centred ferric wheel Fe⊂{Fe₆} of the formula [Fe₇(H₂L)₆(NCS)₆](ClO₄)₃·10H₂O, where H₄L = N,N'-bis(3-carboxylsalicylidene)-1,3-bis(3-aminopropyl)tetramethyldisiloxane, was synthesised and fully characterised. ⁵⁷Fe Mössbauer spectra indicate the presence of high spin (S = 5/2) Fe³⁺ cations adopting a slightly different coordination environment in agreement with the X-ray diffraction structure. There are competing antiferromagnetic exchange interactions along the rim (J₁ = -1.00 cm^-1) and the radius (J₂ = -1.46 cm^-1) of the wheel.