Synthesis, structures, thermal and magnetic properties of two bis(oxalato)cuprate(II) hybrid salts containing pyridinium derivative cations

Abstract

Two bis(oxalato)cuprate(II) hybrid salts, (C 5 H 7 N 2 ) 2 [Cu(C 2 O 4 ) 2 ]·2H 2 O ( 1 ) and (C 7 H 11 N 2 ) 2 [Cu(C 2 O 4 ) 2 ]·5H 2 O ( 2 ) (C 5 H 7 N 2 = 3-aminopyridinium; C 7 H 11 N 2 = 2-amino-4,6-dimethylpyridinium) have been synthesized and characterized by elemental and TGA-DSC analyses, IR and UV–Vis, single-crystal X-ray diffraction and magnetic susceptibility measurements. The polymeric anionic motifs in the two salts are significantly different. In 1 , stacking of [Cu(C 2 O 4 ) 2 ] 2- units through axial Cu⋯O contacts (2.890 Å) yields straight Cu(II) chains, with a prolate CuO6 octahedron around Cu(II) ions, formed by two cis -chelated oxalate anions and two axial O-atoms of neighboring [Cu(C 2 O 4 ) 2 ] 2- units. By contrast, in 2 , stacking of [Cu(C 2 O 4 ) 2 ] 2- units occurs via bis-bidentate oxalate groups, yielding zigzag Cu(II) chains with a distorted CuO6 coordination sphere. Thermal studies confirmed the presence of solvent water molecules in both salts. Magnetic studies revealed weak antiferromagnetic and weak ferromagnetic interactions between Cu(II) ions in 1 and 2 , respectively. The synthesis of two hybrid salts containing bis(oxalato)cuprate(II) units and pyridinium derivatives as counter cations is presented. The solid state structures of these salts highlight different coordination modes of oxalate ligand, leading to straight and zigzag Cu(II) chains for compounds 1 and 2 , respectively. 1 exhibits weak antiferromagnetic interactions whereas 2 exhibits weak ferromagnetic interactions. • Two hybrid salts (C 5 H 7 N 2 ) 2 [Cu(C 2 O 4 ) 2 ]∙2H 2 O ( 1 ) and (C 7 H 11 N 2 ) 2 [CuC 2 O 4 ) 2 ]·5H 2 O ( 2 ) have been synthesized. • Compounds 1 and 2 crystallize in the monoclinic system, space group P 2 1 /c and in triclinic system, space group P -1, respectively. • Hydrogen bonding interactions occur between cations, anions and solvent waters. • Different coordination modes of oxalate ligand are observed in the two (oxalato)cuprate(II) hybrid salts. • Compounds 1 and 2 exhibit weak antiferromagnetic and weak ferromagnetic interactions, respectively.