Two novel copper(II) supramolecular complexes: synthesis, crystal structures, and Hirshfeld surface analysis

Under solvothermal conditions, the reaction of 3-carboxy-1-carboxymethyl-2-oxidopyridinium (H 2 L), and N-donor ligands (2,2′-bipy = 2,2′-bipyridine, 4,4′-bipy = 4,4′-bipyridine) with copper(II) ions, two new complexes biaqua-bis[( μ 2 - 3-carboxylato-1-carboxylatomethyl-2-oxidopyridinium-κ 3 O,O′:O″)-(2,2′-bipyridine-κ 2 N,N′) copper(II)] tetrahydrate (1) and poly{aqua-( μ 2 - 3-carboxylato-1-carboxylatomethyl-2-oxidopyridinium-κ 3 O,O′:O″)-hemi( μ 2 -4,4′-bipyridine-κ 2 N:N′) copper(II)] bihydrate} (2) have been successfully synthesized and structurally confirmed by single-crystal X-ray diffraction analysis techniques and elemental analysis. In complex (1) , the anionic H 2 L ligand connects Cu(II) ions in a μ 2 -η 1 :η 1 :η 1 :η 0 :η 0 mode to form a [Cu(L)] 2 unit, which is further extended into chains via π-π stacking between 2,2′-bipy ligands. Adjacent chains interconnect to form supramolecular layers through additional π-π stacking. Complex (2) was shown to have a chains structure in which the binuclear [Cu(L)] 2 moieties are linked into chains due to the bridging function of the 4,4′-bipy ligand, and further connected by hydrogen bond interactions to form a layered structure. Additionally, the properties of (1) and (2) were characterized by FT-IR, UV–vis, PL, TG and Hirshfeld surfaces analyses.