Schiff Base Complexes Derived from 2-Acetylpyridine, Leucine, and Some Metal Chlorides: Their Preparation, Characterization, and Physical Properties

Abstract

Metal complexes of Cu(II), Co(II), Ni(II), Cr(III), and Fe(III) chlorides with the Schiff base ligand (L) derived from the condensation reaction between leucine and 2-acetylpyridine were prepared. The isolated complexes were characterized by elemental analyses, spectral analyses (IR, UV), thermal analyses (TGA), magnetic measurements, and molar conductivities. The IR spectra show that the ligand can act as a neutral tridentate coordinating to Cu(II), Co(II), or Ni(II) through the pyridyl nitrogen, azomethine nitrogen, and carbonyl oxygen. Another mode of chelation has been suggested that the ligand can act as a mononegative tridentate coordinating to Fe(III) or Cr(III) through the pyridyl nitrogen, azomethine nitrogen, and carboxyl oxygen after displacement of hydrogen from the hydroxyl group. The results suggest tetrahedral geometry around Co(II) and Ni(II), octahedral geometry around Fe(III) and Cr(III), and square-planar geometry around Cu(II). Semi-empirical ZINDO/1 calculations have been used to study the harmonic vibrational spectra of Cu(II) and Fe(III) with the purpose to assist the experimental assignment of the complexes. The molar (Λ) and limiting molar (Λ°) conductances of the prepared complexes were measured experimentally at 298 K. From the values of Λ and Λ°, the ion-pair association constants (K A) and the free energy change of association (ΔG A) were calculated and discussed. Also, the densities (d) and the refractive indices (n) of the prepared complexes were determined in water and 50 % (V/V) dimethylformamide−water solvents at 298 K. Using the values of n and d, the excess refractive indices (n(E) and ń(E)), atomic polarizations (P A), polarizabilities (α), and molar refractions (R m) were calculated and discussed.

Expression of Concern: One‐Step Synthesis of Biaryls under Mild Conditions

“…Magnetic susceptibility measurements further confirmed its geometry. [46,47] From the thermogravimetric (TG) analysis, the weight-loss steps were observed in the approximate temperature ranges 324-395 and 431-462 °C and correspond to 33.82 % (calcd. 32.7 %) mass loss for the C 3 S 5 moiety and 56.5 % (calcd.…”

Spectral characterization, optical band gap calculations and DNA binding of some binuclear Schiff-base metal complexes derived from 2-amino-ethanoic acid and acetylacetone

“…The conditions which favorable the formation of amino acids Schiff base were described in some papers [9][10][11]. On the other hand, the formed organic amino acid Schiff bases are not stable and sensitive to moisture and decompose when exposed to air [12].…”

Solid–solid synthesis, characterization, thermal decomposition and antibacterial activities of zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base ligand

“…Studying Schiff bases of amino acids and their complexes has important significance to bioinorganic chemistry and medicine field. The use of Schiff bases as ligands in the formation of transition-metal complexes had been extensively studied, but the Schiff base ligands and its complexes were previously synthesized in some solvent, and most synthetic methods were performed in ethanol or methanol solution (21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31)(32).…”