Synthesis, structural characterization, and magnetic studies of polynuclear iron complexes with a new disubstituted pyridine ligand

A series of novel polyiron species have been prepared from the reaction of iron chloride with the 2,5-disubstituted pyriclines H2Ln (H2L1 = N,N'-bis(n-butylcarbamoyl)pyridine-2,6-dicarboxamide; H2L2 = N,N'-bis(n-ethylcarbamoyl)pyridine-2,6-dicarboxamide). By small modifications of the experimental conditions under which the reactions are carried out, it has been possible to prepare the quadruply stranded diiron(II) complex [Fe-2(mu-H2L1)(4)(mu-Cl)(2)][FeCl4](2) (1), the metallamacrocycle [Fe-2(mu-H2L1)(2)(THF)(4)Cl-2][FeCl4](2) (2), the hexairon(III) compound [Fe-6(L-1)(2)(mu-OMe)(6)(mu(4)-O)(2)Cl-4] (3), and the mixed-valence trinuclear iron complexes [Fe-3(L-n)(3)(mu(3)-O)] (n = 1, 4; n = 2, 5). The X-ray crystal structures oi 3 and 5 and magnetic studies for all the compounds are herein presented. Interestingly, the structural analysis of 5 at room temperature indicates that one of the iron centers is Fe-III while the other two have an average valenco state between Fe-II and Fe-III. The five complexes herein presented demonstrate the great versatility that the n3w ligand has as a building block for the formation of supramolecular coordination assemblies.