title: Ligand-controlled magnetic interactions in Mn(4) clusters.
abstract: A method is presented to design magnetic molecules in which the exchange interaction between adjacent metal ions is controlled by electron density withdrawal through their bridging ligands. We synthesized a novel Mn(4) cluster in which the choice of the bridging carboxylate ligands (acetate, benzoate, or trifluoroacetate) determines the type and strength of the three magnetic exchange couplings (J(1), J(2), and J(3)) present between the metal ions. Experimentally measured magnetic moments in high magnetic fields show that, upon electron density withdrawal, the main antiferromagnetic exchange constant J(1) decreases from -2.2 K for the [Mn(4)(OAc)(4)] cluster to -1.9 K for the [Mn(4)(H(5)C(6)COO)(4)] cluster and -0.6 K for the [Mn(4)(F(3)CCOO)(4)] cluster, while J(2) decreases from -1.1 K to nearly 0 K and J(3) changes to a small ferromagnetic coupling. These experimental results are further supported with density-functional theory calculations based on the obtained crystallographic structures of the [Mn(4)(OAc)(4)] and [Mn(4)(F(3)CCOO)(4)] clusters.
authors.affiliation: Institute for Molecules and Materials, Radboud University Nijmegen, Toernooiveld 7, 6525 ED Nijmegen, The Netherlands.
authors.forename: Erik
authors.initials: E
authors.lastname: Kampert
authors.forename: Femke F B J
authors.initials: FF
authors.lastname: Janssen
authors.forename: Danil W
authors.initials: DW
authors.lastname: Boukhvalov
authors.forename: Jaap C
authors.initials: JC
authors.lastname: Russcher
authors.forename: Jan M M
authors.initials: JM
authors.lastname: Smits
authors.forename: René
authors.initials: R
authors.lastname: de Gelder
authors.forename: Bas
authors.initials: B
authors.lastname: de Bruin
authors.forename: Peter C M
authors.initials: PC
authors.lastname: Christianen
authors.forename: Uli
authors.initials: U
authors.lastname: Zeitler
authors.forename: Mikhail I
authors.initials: MI
authors.lastname: Katsnelson
authors.forename: Jan C
authors.initials: JC
authors.lastname: Maan
authors.forename: Alan E
authors.initials: AE
authors.lastname: Rowan
mesh_terms: D000085:Acetates / Q000737:chemistry*; D001565:Benzoates / Q000737:chemistry*; D003198:Computer Simulation; D018360:Crystallography, X-Ray; D008024:Ligands; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D014269:Trifluoroacetic Acid / Q000737:chemistry*
chemical_list: D000085:Acetates; D001565:Benzoates; D008024:Ligands; D009942:Organometallic Compounds; D008345:Manganese; D014269:Trifluoroacetic Acid