Copper(I) Complexes with <i>N</i>⁴-Functionalized-1,2,4-Triazole and Bidentate Spacer Ligands: From One- to Three-Dimensional Architecture

The self-assembly of Cu(I) ions with N-[(E)-(4-chlorophenyl)methylidene]-4H-1,2,4-triazol-4-amine (L1) and various spacer ligands yields five different crystalline species: ∞1{[Cu2(μ-L1)2(μ-L2)(CH3CN)2](ClO4)2} (3) (L2 = pyrazine), ∞1{[Cu(L1)(μ-L3)(CH3CN)](ClO4)} (4) and ∞1{[Cu(L1)2(μ-L3)](ClO4)} (5) (L3 = 4,4′- bipyridyl), ∞3{[Cu2(μ-L1)2(μ-L4)2][Cu(μ-L4)3/2(CH3CN)]2(ClO4)4·6CH3CN} (6) and ∞2{[Cu2(μ-L1)2(μ-L4)3(CH3CN)](ClO4)2·CH3CN} (7) (L4 = 1,4-bis(3-pyridyl)-2,3-diaza-1,3-butadiene). Complexes 3−5 are zigzag polymeric one-dimensional (1D) chains, 7 shows a two-dimensional (2D) layered structure, whereas 6 forms a three-dimensional (3D) polymeric structure. In crystals of 3 and 7, the nodes of the polymers are formed by two copper(I) ions bridged by two N1,N2-coordinated triazole ligands L1. Such a coordination mode was previously observed for dimeric complexes {[Cu2(L1)4](ClO4)2}·2CH3CN (1) and {[Cu2(L1)4(CH3CN)2](ClO4)2}·CH3CN (2), and the {Cu-(μ-L1)2-Cu} fragment can be treated as a secondary building unit (SBU) of the polymers. On the other hand, in 4 and 5 the ligands L1 are bound in a monodentate fashion. In 6 two different copper sites are detected: one with SBU coordination mode, while in the other one the metal atom is tetrahedrally coordinated to three L4 spacer ligands and to the acetonitrile molecule. When using L5 as a spacer ligand (L5 = 1,4-bis(4-pyridyl)-2,3-diaza-1,3-butadiene), the microcrystalline product 8 of formula {[Cu(L5)2](ClO4)·H2O} is formed. Irrespective of the metal/L1/L5 molar ratio, no triazole ligand in the final product is observed. The propensity for Cu(I) networks to undergo transitions from a more kinetic to a more thermodynamic product (1 to 2 and 4 to 5) is demonstrated. The role of spacer ligand L4 conformation on metal···metal separation is discussed.