Homo- and heterometallic complexes constructed from hexafluoroacetylacetonato and Schiff-base complexes as building-blocks

摘要

Three new homo- and heterotrimetallic complexes have been synthesized and crystallographically characterized: [Cu-2(saldmpn)(2)(-OCH3)(2)Cu-2(hfac)(2)] (1), [Ni-2(valaepy)(2)(hfac)(2)] (2), [Cu(saldmpn)Co(hfac)(2)] (3) [H(2)saldmpn is the Schiff-base resulting from condensation of salicylaldehyde with 2,2-dimethyl-1,3-diaminopropane and Hvalaepy results from the reaction of o-vanillin with 2-(2-aminoethyl)pyridine)]. The structure of 1 consists of a neutral tetranuclear species that can be viewed as resulting from mutual coordination of one {(hfac)Cu(-OCH3)(2)(Cu(hfac)} and two {Cu(saldmpn)} building blocks. Compound 2 is a binuclear complex that results from two {Ni(hfac)(valaepy} fragments, the nickel(II) ions bridged by the two phenoxide-oxygens. The heterobinuclear complex 3 results from coordination of the [Cu(saldmpn)] metalloligand to cobalt(II) from the {Co(hfac)(2)} unit. The magnetic properties of 1-3 have been investigated from 1.9 to 300K. An overall ferromagnetic behavior is observed for 1 and 2 leading to S=2 low-lying spin state for each one. In the case of 3, a non-magnetic ground state results because of the occurrence of an intramolecular antiferromagnetic coupling between the copper(II) ion and the high-spin cobalt(II) ion, this last one behaving as an effective spin S-eff=1/2 at low temperatures where only the ground Kramers doublet of Co(II) is thermally populated. The values of the intramolecular magnetic couplings in 1-3 are compared with those from the literature on related systems.