Three isostructural disklike heptanuclear Fe
III compounds of the
general formula [Fe
III7(
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3-O)
3(L)
3(
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2CCMe
3)
6(
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1-O
2CCMe
3)
3(H
2O)
3], where L represents a di- or triethanolamine moiety, display a three-blade propeller topolo
gy,with the central Fe atom representin
g the axle or axis of the propeller. This motif corresponds to the theoreticalmodel of a frustrated Heisenber
g star, which is one of the very few solvable models in the area of frustratedquantum-spin systems and can, furthermore, be converted to an octanuclear ca
ge for the case where L istriethanolamine to
give [Fe
III8(
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4O)
3(
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4-tea)(teaH)
3(O
2CCMe
3)
6(N
3)
3]·
1/
2MeCN·
1/
2H
2O or [Fe
III8(
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4O)
3(
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4-tea)(teaH)
3(O
2CCMe
3)
6(SCN)
3]·2MeCN when treated with excess NaN
3 or NH
4SCN, respectively. The core structure is formallyderived from that of the heptanuclear compounds by the replacement of the three aqua li
gands by an {Fe(tea)}moiety, so that the 3-fold axis of the propeller is now defined by two central Fe
III atoms. Ma
gnetic studies on twoof the heptanulcear compounds established unequivocally
S =
5/
2 spin
ground state for these complexes, consistentwith overall antiferroma
gnetic interactions between the constituent Fe
III ions.