title: The mixed-valent manganese [3 x 3] grid [Mn(III)4Mn(II)5(2poap-2H)6](ClO4)10.10 H2O, a mesoscopic spin-1/2 cluster.
abstract: The magnetic susceptibility and low-temperature magnetization curve of the [3 x 3] grid [Mn(III)4Mn(II)5(2poap-2H)6](ClO4)10.10 H2O (1) are analyzed within a spin Hamiltonian approach. The Hilbert space is huge (4,860,000 states), but the consequent use of all symmetries and a two-step fitting procedure nevertheless allows the best-fit determination of the magnetic exchange parameters in this system from complete quantum mechanical calculations. The cluster exhibits a total spin S = 1/2 ground state; the implications are discussed.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern, CH-3012 Bern, Switzerland. waldmann@iac.unibe.ch
authors.forename: Oliver
authors.initials: O
authors.lastname: Waldmann
authors.forename: Hans U
authors.initials: HU
authors.lastname: Güdel
authors.forename: Timothy L
authors.initials: TL
authors.lastname: Kelly
authors.forename: Laurence K
authors.initials: LK
authors.lastname: Thompson