Copper(I) Complexes withN⁴-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]-4 H -1,2,4-triazol-4-amine (L1) and various spacer ligands yields five different crystalline species: ∞ 1 {[Cu 2 (μ-L1) 2 (μ-L2)(CH 3 CN) 2 ](ClO 4 ) 2 } ( 3 ) (L2 = pyrazine), ∞ 1 {[Cu(L1)(μ-L3)(CH 3 CN)](ClO 4 )} ( 4 ) and ∞ 1 {[Cu(L1) 2 (μ-L3)](ClO 4 )} ( 5 ) (L3 = 4,4′- bipyridyl), ∞ 3 {[Cu 2 (μ-L1) 2 (μ-L4) 2 ][Cu(μ-L4) 3/2 (CH 3 CN)] 2 (ClO 4 ) 4 ·6CH 3 CN} ( 6 ) and ∞ 2 {[Cu 2 (μ-L1) 2 (μ-L4) 3 (CH 3 CN)](ClO 4 ) 2 ·CH 3 CN} ( 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 N 1, N 2 -coordinated triazole ligands L1. Such a coordination mode was previously observed for dimeric complexes {[Cu 2 (L1) 4 ](ClO 4 ) 2 }·2CH 3 CN ( 1 ) and {[Cu 2 (L1) 4 (CH 3 CN) 2 ](ClO 4 ) 2 }·CH 3 CN ( 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 ](ClO 4 )·H 2 O} 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.