Abstract
The compound (Hql)2[Fe2(cit)2(H2O)2]·4H2O (1) [ql = quinoline, cit4− = C(O−)(CO−2)(CH2CO−2)2], prepared by reacting ferric nitrate, sodium citrate and quinoline in a molar ratio of 1:1:1 in aqueous solution, was characterized by density measurements, elementary analysis, i.r., X-ray crystallography and magnetic measurements. The X-ray crystallography results reveal that the molecule (1) consists of a binuclear iron(III) citrate anionic complex [Fe2(cit)2(H2O)2]2− and two protonated quinolines [Hql]+. The anionic complex has a centro-symmetric structure, in which two Fe3+ ions are bridged by two μ2-alkoxo groups of the two deprotonated citrate ligands. The other coordination sites of the two slightly distorted octahedra are completed by all the carboxylate groups of the two cit4− ligands in a monodentate mode, and two coordinated water molecules. Magnetic measurements indicate that the two Fe3+ ions are antiferromagnetically coupled below 200 K. A least-squares fit of variable-temperature (1.5–291 K) molar susceptibility data to a dimer model gave the coupling constant J/k = −6.35(7) K and Lande factor g = 2.052(9), where the spin-only Heisenberg–Dirac–van Vleck Hamiltonian is expressed as H = −2JS1S2.
Published Version
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