Mono- and dinuclear CuII complexes of the benzyldipicolylamine (BDPA) ligand: crystal structure, synthesis and characterization

Abstract

The crystal structures of mono- and dinuclear Cu^II trifluoromethanesulfonate (triflate) complexes with benzyldipicolylamine (BDPA) are described. From equimolar amounts of Cu(triflate)₂ and BDPA, a water-bound Cu^II mononuclear complex, aqua(benzyldipicolylamine-κ³N,N',N'')bis(trifluoromethanesulfonato-κO)copper(II) tetrahydrofuran monosolvate, [Cu(CF₃SO₃)₂(C₁₉H₁₉N₃)(H₂O)]·C₄H₈O, (I), and a triflate-bridged Cu^II dinuclear complex, bis(μ-trifluoromethanesulfonato-κ²O:O')bis[(benzyldipicolylamine-κ³N,N',N'')(trifluoromethanesulfonato-κO)copper(II)], [Cu₂(CF₃SO₃)₄(C₁₉H₁₉N₃)₂], were synthesized. The presence of residual moisture in the reaction medium afforded water-bound complex (I), whereas dinuclear complex (II) was synthesized from an anhydrous reaction medium. Single-crystal X-ray structure analysis reveals that the Cu^II centres adopt slightly distorted octahedral geometries in both complexes. The metal-bound water molecule in (I) is involved in intermolecular O-H...O hydrogen bonds with triflate ligands and tetrahydrofuran solvent molecules. In (II), weak intermolecular C-H...F(triflate) and C-H...O(triflate) hydrogen bonds stabilize the crystal lattice. Complexes (I) and (II) were also characterized fully using FT-IR and UV-Vis spectroscopy, cyclic voltammetry and elemental analysis.

Keywords: IR spectroscopy; UV–Vis spectroscopy; benzyldipicolylamine; characterization; copper(II); crystal structure; dimer; intermolecular hydrogen bonds; monomer.