Tuning the interactions from antiferro- to ferro-magnetic by molecular tailoring and manipulating.

Four novel Cu(II) complexes {Na[Cu(4)(hmp)(4)(CHOO)(3)](ClO(4))(2)·H(2)O}(n) (1), [Cu(8)(hmp)(8)(CH(3)COO)(6)](ClO(4))(2) (2), [Cu(4)(hmp)(4)(CH(3)CN)(2)(ClO(4))(2)(H(2)O)(2)](ClO(4))(2) (3), and [Cu(4)(hmp)(4)(CH(3)COO)(2)(H(2)O)(4)](ClO(4))(2)·2H(2)O (4) with Hhmp = 2-(hydroxymethyl)pyridine were prepared by structural modulation at room temperature. Taking advantage of the steric hindrance of the ancillary ligands, the 1D copper chain (1) is successfully cut down into the octa-nuclear copper cluster (2) with the unchanged antiferromagnetic [Cu(4)O(4)] open-cubane that is further separated into weak antiferromagnetic [Cu(4)O(4)] (3) and then modulated to be the ferromagnetic tetra-nuclear [Cu(4)O(4)] cluster (4). The obtained four complexes allow us to systematically investigate their magnetic properties and find the rules for further magnetic investigations. The results showed that there exist antiferromagnetic interactions between Cu(ii) ions in 1-3, while 4 displays ferromagnetic behaviour. The best fitting results to the experimental magnetic susceptibilities gave J(1) = J(2) = J(3) = -2.26 cm(-1), g = 2.11 for 3 and J(1) = 37.05 cm(-1), J(2) = -0.62 cm(-1), J(3) = -0.62 cm(-1), g = 2.13 for 4.