Synthesis, characterization and thermodynamic study of copper(II) complexes with unsymmetric tetradentate Schiff base ligands and X-ray structure of {methyl-2-[N-[2-(5-chloro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate

A set of two Cu(II) complexes, [Cu(cdXsalen)] and [Cu(cdXsalMeen)] derived from Schiff base ligands (H2cdXsalen: methyl-2-{[2-(2-X-phenyl)methylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate and H2cdXsalMeen: methyl-2-{[1-methyl-2-(2-X-phenyl)methylidynenitrilo]ethyl}amino-1-cyclopenteneithiocarb-oxylate where X = hydroxyl, methoxy, nitro, sodiumsulfite, chloro, bromo and H2cdMesalen: methyl-2-{[2-(2-hydroxyphenyl)ethylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate; H2cdPhsalen: methyl-2-{[2-(2-hydroxyphenyl)phenylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate; H2cdMesalMeen: methyl-2-{[1-methyl-2-(2-hydroxyphenyl)ethylidynenitrilo]ethyl}amino-1-cyclopentenedithiocarboxylate; H2cdPhsalMeen: methyl-2-{[1-methyl-2-(2-hydroxyphenyl)phenylidynenitrilo]ethyl}amino-1-cyclopentenedi-thiocarboxylate) with an unsymmetric NNOS coordination sphere have been synthesized and characterized by elemental analysis, IR, UV–Vis and mass spectrometry. The thermodynamic formation constants of the complexes were measured spectrophotometrically, at constant ionic strength 0.1 M (NaClO4), at 25 °C in DMF solvent. The trend of the complex formation for copper is as follow: [Cu(cdMesalen)]>[Cu(cdsalen)]>[Cu(cdPhsalen)][Cu(cdMesalMeen)]>[Cu(cdsalMeen)]>[Cu(cdPhsalMeen)][Cu(cdMesalen)]>[Cu(cdsalen)]>[Cu(cdPhsalen)][Cu(cdMesalMeen)]>[Cu(cdsalMeen)]>[Cu(cdPhsalMeen)] and [Cu(cd5OMesalen)]>[Cu(cd3OMesalen)]>[Cu(cd4OMesalen)][Cu(cd5OMesalMeen)]>[Cu(cd3OMesalMeen)]>[Cu(cd4OMesalMeen)][Cu(cd5OMesalen)]>[Cu(cd3OMesalen)]>[Cu(cd4OMesalen)][Cu(cd5OMesalMeen)]>[Cu(cd3OMesalMeen)]>[Cu(cd4OMesalMeen)] and [Cu(cd5OMesalen)]>[Cu(cdsalen)]>[Cu(cd5Brsalen)]>[Cu(cd5Clsalen)]>[Cu(cd5NO2salen)]>[Cu(cd5SO3Nasalen)][Cu(cd5OMesalMeen)]>[Cu(cdsalMeen)]>[Cu(cd5BrsalMeen)]>[Cu(cd5ClsalMeen)]>[Cu(cd5NO2salMeen)]>[Cu(cd5SO3NasalMeen)][Cu(cd5OMesalen)]>[Cu(cdsalen)]>[Cu(cd5Brsalen)]>[Cu(cd5Clsalen)]>[Cu(cd5NO2salen)]>[Cu(cd5SO3Nasalen)][Cu(cd5OMesalMeen)]>[Cu(cdsalMeen)]>[Cu(cd5BrsalMeen)]>[Cu(cd5ClsalMeen)]>[Cu(cd5NO2salMeen)]>[Cu(cd5SO3NasalMeen)] and [Cu(cdXsalMeen>[Cu(cdXsalen)].[Cu(cdXsalMeen>[Cu(cdXsalen)]. The structure of {methyl-2-[N-[2-(5-chloro-2-phenolate)methylidynenitrilo]ethyl}aminato(-1)-1-cyclopentene-dithiocarboxylatecopper(II), [Cu(cd5Clsalen)], has been determined by X-ray crystallography. The complex shows normal planar geometry around the copper center.

Graphical abstractA set of two Cu(II) complexes, [Cu(cdXalen)] and [Cu(cdXsalMeen)] derived from Schiff base ligands with an unsymmetric NNOS coordination sphere have been synthesized. The thermodynamic formation constants of the complexes were measured spectrophotometrically, at constant ionic strength 0.1 M (NaClO4), at 25 °C in DMF solvent. The structure of {methyl-2-[N-[2-(5-chloro-2-phenolate)methylidynenitrilo]-ethyl}aminato(-1)-1-cyclopentenedithiocarboxylate copper(II), [Cu(cd5Clsalen)], has been determined by X-ray crystallography.Figure optionsDownload full-size imageDownload as PowerPoint slide