title: Enantiopure tetranuclear iron(III) complexes using chiral reduced Schiff base ligands: synthesis, structure, spectroscopy, magnetic properties, and DFT studies.
abstract: Four new tetranuclear iron(III) complexes of formula [{Fe(L)(2)}(3)Fe], 1-4, have been prepared by reacting [Fe(ClO(4))(3)].6H(2)O with H(2)L in methanol. Here, L(2-) is the deprotonated form of N-(2-hyrdoxybenzyl)-l-valinol (H(2)L(1)), N-(2-hyrdoxybenzyl)-l-leucinol (H(2)L(2)), N-(5-chloro-2-hyrdoxybenzyl)-l-leucinol (H(2)L(3)), and N-(2-hyrdoxybenzyl)-l-phenylalaninol (H(2)L(4)). The complexes are prepared in an enantiomeric pure form. The complexes have been characterized with the help of IR, UV-vis, circular dichroism (CD), (1)H, and elemental analyses. The complex [{Fe(L(2))(2)}(3)Fe].CH(3)OH.2H(2)O, 2.CH(3)OH.2H(2)O, crystallizes in enantiomeric pure form containing a propeller-like Fe(4)O(6) core. (1)H and CD spectral studies of the four species are consistent with the structural similarities of the complexes in solution. Variable-temperature magnetic susceptibility of one case shows an intramolecular antiferromagnetic coupling between the Fe(III) ions. Magnetic measurements are in accord with the S = 5 ground state and suggest single molecular magnet behavior. The magnetic exchange coupling constant between the iron centers within the molecule is interpreted using broken-symmetry density functional theory calculation.
authors.affiliation: Inorganic Chemistry Section, Department of Chemistry, Jadavpur University, Kolkata, 700 032, India.
authors.forename: Reena
authors.initials: R
authors.lastname: Singh
authors.forename: Atanu
authors.initials: A
authors.lastname: Banerjee
authors.forename: Enrique
authors.initials: E
authors.lastname: Colacio
authors.forename: Kajal Krishna
authors.initials: KK
authors.lastname: Rajak
mesh_terms: D002942:Circular Dichroism / Q000379:methods; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000138:chemical synthesis* / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008280:Magnetics; D008956:Models, Chemical; D008958:Models, Molecular; D008968:Molecular Conformation; D012545:Schiff Bases / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013237:Stereoisomerism
chemical_list: D005290:Ferric Compounds; D008024:Ligands; D012545:Schiff Bases