Nanosized clusters of transition metals are recent attractive research targets due to their great potential applications in the development of “intelligent” multifunctional materials for information storage and quantum computation. The size of metal clusters can be controlled through a proper choice of the metal ions employed and by the judicious linkage of suitable bridging ligands, and flexible polydentate N-donor alcohol ligands have been shown to be good candidates for generation of such nanosized metal clusters. Magnetic behavior of four new octanuclear iron (III) carboxylate clusters: [Fe8O3(is)9(tea)(teaH)3] (1•MeCN•H2O; 2• MeCN •2H2O), [Fe8O3(is)6(N3)3(tea)(teaH)3] (3) and [Fe8O3(piv)6(N3)3(tea)(teaH)3]•EtOH (4) (where is = isobutyric acid; Hpiv = pivalic acid; teaH3 = triethanolamine) has been investigated. The magnetic susceptibility data of 1-4 are depicted in Fig. 1 as open circles. Fig.1. Temperature dependence of the magnetic susceptibility χm of 1-4 at 0.1 Tesla; inset: temperature dependence of the corresponding effective magnetic moment μeff. Fig.2. Coupling scheme of 1-4 using the example of compound 4: a) front view, b) side view. All compounds approach an effective magnetic moment of approximately μeff = 9.6 μB at 290 K which is well shown below the spin-only value of 16.7 μB expected for eight non-interacting highspin FeIII centers, thus indicating dominant antiferromagnetic exchange interactions within each compound. In addition, the effective magnetic moment continuously decreases by lowering the temperature supporting the interpretation of dominant antiferromagnetic interactions. The calculations of the computer program wxJFinder [1] show that 15 of the 28 exchange interaction parameters are negligible. 12 of the remaining 13 parameters are divided into four categories that represent each three (almost) identical parameters. Thus, all compounds are described by an effective Hamiltonian that contains five independent exchange parameters Ji as depicted in Fig. 2 (notation: Ĥex = Σk<l –2Ji Ŝk⋅Ŝl). Thus, taking the propeller model, the compounds are characterized by moderate antiferromagnetic interactions along the edges and weak antiferromagnetic interactions at the tips. A moderate ferromagnetic interaction is found along the axis, the shortest distance of FeIII–FeIII within the compounds that form in combination with their bridging oxo-ligand an almost right-angled triangle.