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 (teaH(3)) based octanuclear cluster [Fe-III O-8(3)(O2CCH2CH3)(6)(tea)(teaH)(3)(F)(3)] center dot 0.5MeOH center dot 0.5H(2)O ( 1) is reported. The octanuclear core in 1 has only been observed once before in the analogous teaH(3) based [Fe8O3(O2CPh)(9)(tea)(teaH)(3)] center dot 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 [Fe-III O-3(O2CCMe3)(6)(H2O)(3)](O2CCMe3) with the tripodal ligands 1-[N,N-bis(2-hydroxyethyl)amino]- 2- propanol (bheapH(3)) and triethanolamine (teaH(3)) gives [Fe-III O-7(3)(O2CCMe3)(9)(bheapH)(3)( H2O)(3)] ( 2) and [(Fe7O3)-O-III(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).