Heptanuclear iron(III) triethanolamine clusters exhibiting ‘millennium dome’-like topologies and an octanuclear analogue with ground spin states of S = 5/2 and 0, respectively

The synthesis and structural determination of the tripodal triethanolamine (teaH3) based octanuclear cluster [FeIII8O3(O2CCH2CH3)6(tea)(teaH)3(F)3]·0.5MeOH·0.5H2O (1) is reported. The octanuclear core in 1 has only been observed once before in the analogous teaH3 based [Fe8O3(O2CPh)9(tea)(teaH)3]·MeCN cluster and, as observed in that case, magnetic susceptibility measurements on 1 indicate a ground spin state of S = 0. Reaction of the trinuclear complex [FeIII3O(O2CCMe3)6(H2O)3](O2CCMe3) with the tripodal ligands 1-[N,N-bis(2-hydroxyethyl)-amino]-2-propanol (bheapH3) and triethanolamine (teaH3) gives [FeIII7O3(O2CCMe3)9(bheapH)3(H2O)3] (2) and [FeIII7O3(O2CCMe3)9(teaH)3(H2O)3] (3), respectively. The cores in 2 and 3 are dome-like in topology, an architecture unseen in any heptanuclear clusters reported to date. Magnetisation and susceptibility measurements show that clusters 2 and 3 exhibit ground spin states of S = 5/2. Low temperature EPR measurements confirm these ground spin states and yield zero-field splitting parameters of D = 0.28 cm−1 and E/D of 0.21 (for 3).