Novel dinuclear and polynuclear copper(II)-pyrazine-2,3-dicarboxylate supramolecular complexes with 1,3-propanediamine, N,N,N′,N′-tetramethylethylenediamine and 2,2′-bipyridine

Three novel Cu(II)-pyrazine-2,3-dicarboxylate complexes with 1,3-propanediamine (pen), Cu₂(μ-pzdc)₂(pen)₂] · 2H₂O (1), N,N,N′,N′-tetramethylethylenediamine (tmen), {Cu(μ-pzdc)(tmen)] · H₂O}_n(2), and 2,2′-bipyridine (bipy), {Cu(μ-pzdc)(bipy)]·H₂O}_n(3) have been synthesized and characterized by means of elemental and thermal analyses, magnetic susceptibilities, IR and UV/vis spectroscopic studies. The molecular structures of dinuclear (1) and polynuclear (2 and 3) complexes have been determined by the single crystal X-ray diffraction technique. The pyrazine-2,3-dicarboxylate acts as a bridging ligand through oxygen atom of carboxylate group and N atom of pyrazine ring and one oxygen atom of neighboring carboxylate. It links the Cu(II) ions to generate a distorted square pyramidal geometry forming a one-dimensional (1D) chain. Adjacent chains of 1 and 2 are then mutually linked via hydrogen bonding interactions, which are further assembled to form a two and three-dimensional network, respectively. The chains of complex 3 are further constructed to form three-dimensional framework by hydrogen bonding, C–H?π and ring?ring stacking interactions. In the complexes, Cu(II) ions have distorted square pyramidal geometry. Thermal analyses properties and thermal decomposition mechanism of complexes have been investigated by using thermal analyses techniques (TG, DTG and DTA).