TY - JOUR
T1 - The sterically hindered salicylaldimine ligands with their copper(II) metal complexes
T2 - Synthesis, spectroscopy, electrochemical and thin-layer spectroelectrochemical features
AU - Tas, Esref
AU - Kilic, Ahmet
AU - Konak, Nazli
AU - Yilmaz, Ismail
PY - 2008/2/26
Y1 - 2008/2/26
N2 - The synthesis, structure, spectroscopic and electro-spectrochemical properties of sterically constrained Schiff-base ligands (LnH) (n = 1, 2, and 3) (L = N-[m-(methylmercapto)aniline]-3,5-di-t-butylsalicylaldimine, m = 4, 3, and 2 positions, respectively) and their copper(II) complexes [Cu(Ln)2] are described. Three new dissymmetric bidentate salicylaldimine ligands containing a donor set of ONNO were prepared by reaction of different primary amine with 3,5-di-t-butyl-2-hydroxybenzaldehyde (3,5-DTB). The copper(II) metal complexes of these ligands were synthesized by treating an methanolic solution of the appropriate ligand with an equimolar amount of Cu(Ac)2 · H2O. The ligands and their copper complexes were characterized by FT-IR, UV-Vis, 1H and 13C NMR and elemental analysis methods in addition to magnetic susceptibility, molar conductivity, and spectroelectrochemical techniques. Analytical data reveal that copper(II) metal complexes possess 1:2 metal-ligand ratios. On the basis of molar conductance, the copper(II) metal complexes could be formulated as [Cu(Ln)2] due to their non-electrolytic nature in dimethylforamide (DMF). The room temperature magnetic moments of [Cu(Ln)2] complexes are in the range of 1.82-1.90 B.M which are typical for mononuclear of Cu(II) compounds with a S = 1/2 spin state. The complexes did not indicate antiferromagnetic coupling of spin at this temperature. Electrochemical and thin-layer spectroelectrochemical studies of the ligands and complexes were comparatively studied in the same experimental conditions. The results revealed that all ligands displayed irreversible reduction processes and the cathodic peak potential values of (L3H) are shifted towards negative potential values compared to those of (L1H) and (L2H). It is attributed to the weak-electron-donating methyl sulfanyl group substituted on the ortho (m = 2) position of benzene ring. Additionally, all copper complexes showed one quasi-reversible one-electron reduction process in the scan rates of 0.025-0.50 V s-1, which are assigned to simple metal-based one-electron processes; [Cu(2+)(Ln)2] + e- → [Cu(1+)(Ln)2]-. The spectral changes corresponding to the ligands and complexes during the applied potential in a thin-layer cell confirmed the ligand and metal-based reduction processes, respectively.
AB - The synthesis, structure, spectroscopic and electro-spectrochemical properties of sterically constrained Schiff-base ligands (LnH) (n = 1, 2, and 3) (L = N-[m-(methylmercapto)aniline]-3,5-di-t-butylsalicylaldimine, m = 4, 3, and 2 positions, respectively) and their copper(II) complexes [Cu(Ln)2] are described. Three new dissymmetric bidentate salicylaldimine ligands containing a donor set of ONNO were prepared by reaction of different primary amine with 3,5-di-t-butyl-2-hydroxybenzaldehyde (3,5-DTB). The copper(II) metal complexes of these ligands were synthesized by treating an methanolic solution of the appropriate ligand with an equimolar amount of Cu(Ac)2 · H2O. The ligands and their copper complexes were characterized by FT-IR, UV-Vis, 1H and 13C NMR and elemental analysis methods in addition to magnetic susceptibility, molar conductivity, and spectroelectrochemical techniques. Analytical data reveal that copper(II) metal complexes possess 1:2 metal-ligand ratios. On the basis of molar conductance, the copper(II) metal complexes could be formulated as [Cu(Ln)2] due to their non-electrolytic nature in dimethylforamide (DMF). The room temperature magnetic moments of [Cu(Ln)2] complexes are in the range of 1.82-1.90 B.M which are typical for mononuclear of Cu(II) compounds with a S = 1/2 spin state. The complexes did not indicate antiferromagnetic coupling of spin at this temperature. Electrochemical and thin-layer spectroelectrochemical studies of the ligands and complexes were comparatively studied in the same experimental conditions. The results revealed that all ligands displayed irreversible reduction processes and the cathodic peak potential values of (L3H) are shifted towards negative potential values compared to those of (L1H) and (L2H). It is attributed to the weak-electron-donating methyl sulfanyl group substituted on the ortho (m = 2) position of benzene ring. Additionally, all copper complexes showed one quasi-reversible one-electron reduction process in the scan rates of 0.025-0.50 V s-1, which are assigned to simple metal-based one-electron processes; [Cu(2+)(Ln)2] + e- → [Cu(1+)(Ln)2]-. The spectral changes corresponding to the ligands and complexes during the applied potential in a thin-layer cell confirmed the ligand and metal-based reduction processes, respectively.
KW - Copper(II) complexes
KW - Electrochemistry
KW - Molar conductivity
KW - Salicylaldimine
KW - Thin-layer spectroelectrochemistry
UR - http://www.scopus.com/inward/record.url?scp=38749130431&partnerID=8YFLogxK
U2 - 10.1016/j.poly.2007.11.038
DO - 10.1016/j.poly.2007.11.038
M3 - Article
AN - SCOPUS:38749130431
SN - 0277-5387
VL - 27
SP - 1024
EP - 1032
JO - Polyhedron
JF - Polyhedron
IS - 3
ER -