Nickel (II) and Copper (II) Complexes Derived from NNOS Donor Unsymmetrical Tetradentate Schiff Base Ligands: Synthesis, Characterization, and Thermodynamic Studies

Abstract

A set of eight unsymmetrical tetradentate Schiff bases (cdPhsalpd = Methyl-2-{[3-(2-hydroxyphenyl)phenylidynenitrilo]propyl}amino-1-cyclopentenedithiocarboxylate; cd3-, 4-, 5-OMesalpd = Methyl-2-{[3-(2-hydroxy 3-, 4-, 5-methoxyphenyl)methylidynenitrilo]propyl} amino-1-cyclopentenedithiocarboxylate; cd5Clsalen = Methyl-2-{[3-(2-hydroxy-5-chloro phenyl)methylidynenitrilo]propyl}amino-1-cyclopentenedithiocarboxylate; cd5Brsalen = Methyl-2-{[3-(2-hydroxy-5-bromophenyl)methylidynenitrilo]propyl}amino- 1-cyclopente- nedithiocarboxylate; cd5NO2salen = Methyl-2-{[3-(2-hydroxy-5-nitrophenyl)methylidyne- nitrilo]propyl}amino-1-cyclopentenedithiocarboxylate; and cd5SO3Na = Methyl-2-{[3- (2-hydroxy-5-sodiumsulfitephenyl)methylidynenitrilo]propyl} amino-1-cyclopentenedithi- ocarboxylate, have been obtained by condensation of methyl-2-(3-aminopropylamino) cyclopentenedithiocarboxylate (Hcdpd) with some substituted salicylaldehydes, 2-hydroxy acetophenone, and 2-hydroxy benzophenone, which present a NNOS coordination spheres. Also, the metal complexes (M = Cu, Ni) of these ligands were prepared and characterized by elemental analysis, IR, 1H NMR, UV-Vis, and mass spectrometry.The formation constants and the thermodynamic free energies were measured using UV-Vis spectrophotometry titration for 1:1 complex formation at constant ionic strength 0.1 M (NaClO4) at 25°C in DMF. The trend of the complex formation of the nickel and copper complexes is as follows: [M(cdMesalpd)] > [(Mcdsalpd)] > [M(cdPhsalpd)] and [M(cd5OMesalpd)] > [M(cd3OMesalpd)] > [M(cd4OMesalpd)] and [M(cd5OMesalpd)] > [M(cdsalpd)] > [M(cd5Brsalpd)] > [M(cd5Clsalpd)] > [M(cd5SO3Nasalpd)] > [M(cd5NO2salpd)]. Our results revealed the thermodynamic formation constant, K f, and the free energy values for Cu(II) complexes are higher than the Ni(II) complexes. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.