The reaction of the trimetallic species [Fe3O(PhCOO)(6)(H2O)(3)]NO3 with 1,1,1-tris(hydroxymethyl)ethane (H(3)thme) affords either the octametallic species [Fe-8(PhCOO)(12)(thme)(4)] 1 or the hexadecametallic species [Fe-16(EtO)(4)(PhCOO)(16)-(Hthme)(12)](NO3)(4) 2, depending on the nature of the solvent used for crystallization. The structure of 1 can be described as a nonplanar wheel of eight Fe-III ions bridged by a combination of PhCOO- and thme(3-) ligands,and 2 as a nonplanar wheel of sixteen Fe-III ions bridged by PhCOO-, Hthme(2-), and EtO- ligands. Both compounds can be broken down into simple units of two metal ions and the bridging ligands that connect them. The best fits of the chi vs T curves in the 300-10 K temperature range were obtained with the parameters g = 2.0, J, = -24.0 cm(-1), and J(2) = -8.59 cm(-1) for [Fe-8] and g = 2.0, J(1) = -25.0 cm(-1), J(2) = -11.73 cm(-1), and J3 = -69.3 cm(-1) for [Fe-16]. Density functional theory (DFT) calculations show that the antiferromagnetic interactions between the metals in the dinuclear units decrease when two types of bridging ligands are present, as expected for an orbital counter-complementarity effect.