Synthesis, crystal structure, magnetic and electrochemical studies of two copper complexes with carboxylate rich dinucleating ligand

Three new copper compounds of a symmetric dinucleating ligand, N,N′-bis[2-carboxybenzomethyl]-N,N′-bis[carboxymethyl]-1,3-diaminopropan-2-ol (H5ccdp) with diverse coordinating groups, have been synthesized and studied in the solid state as well as in solution. In acetonitrile/H2O solution, the reaction of stoichiometric amounts of Cu(NO3)2·2.5H2O and the ligand H5ccdp, in the presence of K2CO3, produced a dinuclear copper compound, K3[Cu2(ccdp)(μ-CO3)]·7H2O·C3H6O, K3[1]·7H2O·C3H6O. Whereas in an alkaline methanol/water solution, the reaction of Cu(ClO4)2·6H2O and the ligand H5ccdp gave a slightly different dinuclear copper compound, Na3[Cu2(ccdp)(μ-CO3)]·5H2O, Na3[1]·5H2O. The reaction of Cu(ClO4)2·6H2O and the ligand H5ccdp, in the presence of NaOH in water yielded a tetranuclear copper compound, Na2[Cu2(ccdp)(H2O)(μ-OH2)]2·15H2O, Na2[2]·15H2O. The structures of the all three complexes were determined using single crystal X-ray diffraction analyses. Variable-temperature magnetic susceptibility studies on the powder samples of the complexes showed antiferromagnetic behavior. Electrochemical studies in aqueous solutions of these negatively charged complex ions showed fairly assessable oxidations.

Three new di- and tetranuclear copper compounds K3[Cu2(ccdp)(μ-CO3)]·7H2O·C3H6O (K3[1)]·7H2O·C3H6O), Na3[Cu2(ccdp)(μ-CO3)]·5H2O (Na3[1]·5H2O), and Na2[Cu2(ccdp)(μ-OH2)2]2·15H2O (Na2[2]·15H2O) are reported. In the dinuclear copper comounds K3[1)]·7H2O·C3H6O and Na3[1]·5H2O, the copper ions are symmetrically coordinated to the heptadentate part of the dinucleating ligand with a carbonate ligand bridging the two metals. The tetranuclear copper compound Na2[2]·15H2O consists of two dinuclear subunits bridged by two water molecules. The four copper ions possess alternating 5- and 6-coordination sites. The complexes reveal the overall antiferromagnetic coupling between Cu(II) ions at wide temperature ranges. Electrochemical studies in aqueous solutions of these negatively charged complex ions showed fairly assessable oxidations.Figure optionsDownload as PowerPoint slideHighlights
► Three new polynuclear copper complexes have been synthesized and characterized.
► The structures of the complexes were determined using single crystal X-ray diffraction analyses.
► The solid state structure of 1 and 2 contain a carbonato ligand bridging the two copper ions in a syn–syn coordination.
► Variable-temperature magnetic susceptibility indicated antiferromagnetic behavior.
► Electrochemical studies reveal fairly assessable oxidations.