The synthesis of three new Cu5, Cu8 and Cu12 clusters via the use of a semi-flexible aminotriazine-based bis-methylpyridine ligand.

Abstract

The synthesis of three new polynuclear Cu5, Cu8 and Cu12 clusters has been achieved using a semi-flexible aminotriazine-based bis-methylpyridine ligand, N2,N2-dibenzyl-N4,N6-di(pyridylmethyl)-1,3,5-triazine-2,4,6-triamine (H2dpmta). The reaction of Cu(ClO4)2·6H2O with H2dpmta in i-PrOH afforded the complex [Cu5(OH)4(H2dpmta)2(ClO4)4(H2O)4](ClO4)2·Et2O·5i-PrOH (1). A similar reaction of Cu(ClO4)2·6H2O and H2dpmta in the presence of PhCO2Na in i-PrOH/CH2Cl2 gave the complex [Cu8(OH)6(O2CPh)4(H2dpmta)2(ClO4)4(i-PrOH)2](ClO4)2·2CH2Cl2·2i-PrOH (2). The complex [Cu12O3(OH)2(Hdpmta)2(dpmta)2(O2CMe)8](ClO4)2·2MeCN (3) was produced from the reaction of [Cu2(O2CMe)4]·2H2O with H2dpmta and NaClO4 in MeCN/CH2Cl2. Single-crystal X-ray diffraction measurements were carried out on these complexes. The Cu5 cluster of 1 consisted of a planar [Cu5(μ-OH)4]6+ core in a rectangle-like arrangement. The Cu12 cluster of 2 represented a [Cu8(μ3-OH)4(μ-OH)2]10+ core infusion of two [Cu4(OH)2]6+ butterfly subunits. Complex 3 possesses a bent [Cu12(μ4-O)3(μ-OH)2]16+ core structure, in which a central [Cu4(μ4-O2-)] square planar moiety was fused with two butterfly-like [Cu4(μ4-O)(μ3-OH)] subunits. The magnetic properties of these three complexes were characterized by the measurements of variable-temperature and field magnetic susceptibility. The magnetic analysis showed that a strong antiferromagnetic interaction was mediated between Cu(ii) ions by the single OH- bridge in 1 and resulted a S = 3/2 spin ground state. In complex 2, both intramolecular antiferro- and ferromagnetic interactions were dominated between Cu(ii) ions resulting a spin ground state of S = 2. Indeed, complex 3 displayed an overall antiferromagnetic coupling.