Synthesis and characterization of iron(III) complexes of N4 Schiff base macrocycles

Iron(III) complexes of the diprotic N-4 Schiff base macrocycles, 7,8,15,16,17,18-hexahydrow-dibenzo [e,m] [1,4,8,11] tetraazacyclotetradecine (H-2(2,2 mac)) and 8,9,16,17,18,19-hexahydro-7H-dibenzo [e,n] [1,4,8,12] tetraazacyclopentaadecine (H-2(3,2mac)),were prepared by the metathesis reaction of anhydrous iron(III) bromide with the disodium or magnesium complexes of the dianionic ligands in THF under an inert atmosphere. The complexes exhibit the intermediate spin state as evidenced by magnetic susceptibility and Mossbauer spectroscopy. Fe(3,2 mac)Br is structurally characterized as a distorted square pyramid with the four nitrogen atoms in the basal positions and the bromide occupying the axial site. The average iron to nitrogen bond distance is 1.921 Angstrom. (C) 1999 Elsevier Science S.A. All rights reserved.