title: Binding of ligands containing carbonyl and phenol groups to iron(iii): new Fe6, Fe10and Fe12coordination clusters.
abstract: The initial use of ligands 2'-hydroxyacetophenone (HL1), 2-hydroxybenzophenone (HL2) and 2,2'-dihydroxybenzophenone (H2L3) in iron(iii) chemistry is described. The syntheses and crystal structures are reported for five iron(iii) clusters: [Fe10O4(OMe)14(L1)6(MeOH)2](NO3)2·3MeOH (1·3MeOH), [Fe12O4(OH)(OMe)17(L1)8](ClO4)2·2H2O (2·2H2O), [Fe10O4(OMe)14Cl4(L2)4(MeOH)2] (3), [Fe10O4(OMe)14(L2)6(py)2](ClO4)2·MeOH (4·MeOH), where py = pyridine, and [Fe6O2(OEt)6(O2CMe)2(L3)2(HL3)2] (5). The molecular structures of the decanuclear clusters 1, 3 and 4 are organized around a {Fe10(μ4-O)4(μ3-OMe)2(μ-OMe)12}8+core consisting of ten {Fe3O4} face-sharing defective cubane units. The core of 2 consists of a {Fe12(μ4-O)4(μ3-OMe)4(μ-OH)(μ-OMe)13}10+unit composed of twelve {Fe3O4} face-sharing defective cubanes. The ligands (L1)-and (L2)-in 1-4 adopt the O,O'-bidentate chelating coordination mode and their roles are to terminate the further aggregation of the FeIII/O2-/RO-cores. Complex 5 contains the {Fe6(μ4-O)2(μ-OEt)6(μ-Ocarbonyl)2}4+core, where the μ-Ocarbonylatoms are the bridging carbonyl oxygens of the two η1:η2:η1:μ (L3)2-ligands; the (HL3)-groups behave as Ophenolate, Ocarbonyl-bidentate chelating ligands with the neutral hydroxyl group being unbound to the FeIIIatoms. The core is composed of four {Fe3O4} face-sharing defective cubanes. The FeIIIatoms in 1-5 are all six-coordinate with distorted octahedral geometries. The IR spectra of the complexes are discussed in terms of the known coordination modes of the ligands and the ionic character of nitrates and perchlorates. Variable-temperature magnetic susceptibility and variable-field magnetization measurements establish that 2, 3 and 5 have S = 3, 0 and 5 ground states, respectively. The susceptibility data for 5 were fitted using a 3-J model indicating the simultaneous presence of both antiferromagnetic and ferromagnetic FeIIIFeIIIexchange interactions. Known magnetostructural correlations in oxido-bridged iron(iii) systems have been applied to rationalise the magnetic behaviour of the three clusters. The results of the present study demonstrate the utility of HL1, HL2and H2L3in the stabilisation of robust iron(iii)/oxido/alkoxido clusters.
authors.affiliation: Department of Chemistry, University of Patras, 26504 Patras, Greece. nastopoulos@chemistry.upatras.gr.
authors.forename: Alexandros A
authors.initials: AA
authors.lastname: Kitos
authors.affiliation: Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus and School of Chemistry, National University of Ireland Galway, Galway, Ireland.
authors.forename: Constantina
authors.initials: C
authors.lastname: Papatriantafyllopoulou
authors.affiliation: Department of Chemistry, University of Cyprus, 1678 Nicosia, Cyprus.
authors.forename: Anastasios J
authors.identifier: http://orcid.org/0000-0002-4804-3822
authors.initials: AJ
authors.lastname: Tasiopoulos
authors.affiliation: Department of Chemistry, University of Patras, 26504 Patras, Greece. nastopoulos@chemistry.upatras.gr.
authors.forename: Spyros P
authors.initials: SP
authors.lastname: Perlepes
authors.affiliation: Departament de Quimica Inorgànica i Orgànica, Seccio Inorgànica and Institute of Nanoscience and Nanotechnology (IN2UB), Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain. albert.escuer@qi.ub.es.
authors.forename: Albert
authors.initials: A
authors.lastname: Escuer
authors.affiliation: Department of Chemistry, University of Patras, 26504 Patras, Greece. nastopoulos@chemistry.upatras.gr.
authors.forename: Vassilios
authors.identifier: http://orcid.org/0000-0003-4190-1342
authors.initials: V
authors.lastname: Nastopoulos