HYDROXIDE-BRIDGED DIIRON(III) COMPLEXES OF TETRAAMINODIPHENOL MACROCYCLIC LIGANDS - STRUCTURE AND PROPERTIES

Some dinuclear iron(III) complexes derived from two tetraaminodiphenol macrocyclic ligands, one (H(2)L(1)) contains two -NH(CH2)(3)NH- and t he other (H(2)L(2)) one -NH(CH2)(3)NH- and one -NH(CH2)(2)NH- units, a nd an acyclic tetradentate ligand {H(2)L(3) N,N'-bis(2-hydroxybenzyl)- 1,3-diaminopropane} have been synthesised and studied. In all of the m acrocyclic complexes [Fe-2(mu-OH)(2)(H L(1))(2)][ClO4](2) 1, [Fe-2(mu- OH)(2)L(2)(1)]. 2H(2)O 2, [Fe(H(2)L(1)) (H2O)(2)] [ClO4](3) . H2O 3, [ Fe-2(mu- OH)(2)(H(2)L(2))(2)]-[ClO4]4 . 2H(2)O 4, [Fe-2(mu-OH)(2)L22]. 2H(2)O 5 and [Fe-2(mu-OH)(2)L(2)(3)] 6 only N2O2 donation to the meta l centres occurs, while the two unco-ordinated amino nitrogens either remain singly protonated (2 and 5) or one (1) or both of these (3 and 4) is doubly protonated. Variable-temperature magnetic susceptibility data for 1, 4 and 6 indicate weak antiferromagnetic-exchange interacti ons in each case with J values of: -5.5 (1), -7.3 (4) and -11.8 cm(-1) (6). The isomer-shift and quadrupole-splitting values for 1 at 77 K a re 0.46 and 0.43 mm s(-1). respectively. The redox chemistry of 1 has been studied by cyclic voltammetry and its crystat structure has been determined: monoclinic, space group P2(1)/c, a = 13.448(1), b = 14.847 (1), c = 13.442(1) Angstrom, beta = 91.48 (1)degrees, Z = 2, R = 0.048 and R' = 0.050. The two edge-sharing FeO4N2 octahedra are distorted a nd connected by a centre of inversion.