A copper-based coordination polymer formed through synergistic bridging of 1,2,4-triazole and acetate anions: synthesis, crystal structure and magnetic properties

Abstract

A Cu(II) coordination polymer, [Cu2(pztrz)2(μ-CH3COO)(CH3COO)]·3H2O (1), derived from mono-substituted 1,2,4-triazole derivative 3-(pyrazinyl)-1,2,4-triazole (Hpztrz) is isolated and structurally characterized. X-ray structural analysis shows that Hpztrz ligands and acetate anions demonstrate different coordination modes in complex 1. The two Cu(II) ions are bridged by the 1,2,4-triazole ring of Hpztrz to form a dinuclear unit, which is further linked by two bridging acetate anions to form a tetranuclear Cu4 unit. Interestingly, each Cu4 unit is connected to another four Cu4 units through the outer pyrazinyl of Hpztrz, resulting in a two-dimensional (2D) layer structure. Consecutive layers are further packed into three-dimensional (3D) structures through interlayer hydrogen-bonding interactions. Furthermore, variable-temperature magnetic susceptibility studies reveal that the antiferromagnetic interactions are mediated through 1,2,4-triazole-N1,N2 bridges and acetate bridges with coupling constants of J1 = − 69.98 cm−1 and J2 = − 2.15 cm−1. Synergistic co-coordination of 1,2,4-triazole and acetate ions with Cu(II) ions led to a dinuclear unit, then to a Cu4 unit and finally to a 2D layer. Consecutive layers are further packed into a 3D framework through interlayer hydrogen-bonding interactions. Furthermore, variable-temperature magnetic susceptibility studies indicated the existence of antiferromagnetic coupling between the Cu(II) ions.