title: Synthesis and magnetism of oxygen-bridged tetranuclear defect dicubane Co(II) and Ni(II) clusters.
abstract: Reaction of aqueous/ethanolic solutions of CoCl2.6H2O and nitrilotripropionic acid (H3ntp=N(CH2CH2COOH)3) in the presence of potassium hydroxide affords the hydroxy-bridged tetranuclear cluster [Co4mu3-OH)2(H2O)6(ntp)2].2H2O (1). The Ni(II) analogue [Ni4(mu3-OH)2(H2O)6(ntp)2].2H2O (2) can also be isolated using aqueous solutions and Ni(SO4).7H2O as metal salt. With small changes in reaction conditions the methoxy-bridged analogue, [Ni4(mu3-OMe)2(H2O)6(ntp)2](3), can also be isolated. In these tetramers the M(II) ions are oxygen-bridged and exhibit a defect dicubane-like core with two missing vertices. The magnetic properties have been studied for all three clusters and reveal competing antiferromagnetic and ferromagnetic interactions between the four Co(II) ions in 1 and ferromagnetic coupling between the four Ni(II) ions in 2 and 3. In all three compounds the individual clusters order antiferromagnetically at Neel temperatures below 1 K.
authors.affiliation: Institut für Anorganische Chemie der Universität Karlsruhe, Germany.
authors.forename: Philippa
authors.initials: P
authors.lastname: King
authors.forename: Rodolphe
authors.initials: R
authors.lastname: Clerac
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wernsdorfer
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Anson
authors.forename: Annie K
authors.initials: AK
authors.lastname: Powell