Monomeric, trimeric and polymeric assemblies of dicopper(ii) complexes of a triazolate-containing Schiff-base macrocycle

Abstract

The new triazolate-containing Schiff-base macrocyclic ligand L2²⁻ has been synthesised as [Pb^II₂(L2)](ClO₄)₂, 1, by the [2 + 2] cyclisation reaction of 3,5-diacetyl-1H-1,2,4-triazole and 1,3-diaminopropane using lead(II) template ions. The macrocycle provides four nitrogen atoms, two imine and two triazolate donors, as equatorial donor atoms to each of the two metal ions in the macrocycle. A series of copper(II) complexes of the L2²⁻ macrocycle has been produced with a variety of axial donors. Each copper complex has been structurally characterised by X-ray diffraction and three different structural types can be distinguished: monomeric, trimeric and polymeric. These different types arise from adding a different ratio of thiocyanate ions to the copper(II) transmetallation reaction of [Pb^II₂(L2)](ClO₄)₂ (1). The monomeric dicopper(II) macrocyclic complexes include [Cu^II₂(L2)(NCMe)₂](ClO₄)₂ (2) and [Cu^II₂(L2)(NCS)₂] (3). The trimeric complex {[Cu^II₂(L2)]₃(NCS)₂}(ClO₄)₄ (4) consists of three dicopper(II) macrocyclic complexes bridged by two thiocyanate ions. The thiocyanate-bridged polymeric complex {[Cu^II₂(L2)(NCS)][Cu^II₂(L2)(SCN)](ClO₄)₂}_x (5) comprises two types of macrocyclic units in the repeating unit. A second polymeric isomer {[Cu^II₂(L2)(NCS)](ClO₄)}_x (6), incorporating a more symmetrical thiocyanate-bridging mode that has only one type of macrocyclic unit in the repeating unit, is also reported.