Synthesis, Characterization and Structural Studies of Mixed L-Glutamic Acid and L-Phenylalanine Complexes of Fe(III), Mn(II), Cu(II) and Zn(II)

Fe(III), Mn(II), Cu(II), and Zn(II) complexes containing mixed L-glutamic acid (Glu) and L-phenylalanine (Phn) ligands were synthesized, characterized, and their structures determined using a solvothermal technique. All of the complexes showed excellent solubility in DMSO at 25°C, but they were insoluble in acetone. [Zn(Glu)(Phn)]H₂O⁻ was shown to be diamagnetic (μₑff = 0.19 B.M.) by magnetic susceptibility studies, whereas the Fe(III), Mn(II), and Cu(II) complexes showed paramagnetic behavior (μₑff values of 7.81, 6.09, and 1.63 B.M., respectively). Molar conductivity measurements indicated that all complexes except [Fe(Glu)(Phn)(H₂O)₂] (Λ = 15.24 Ω⁻¹ mol⁻¹ cm²) exhibited electrolytic behavior in solution. UV-Visible spectroscopy revealed bathochromic shifts in absorption spectra, with [Zn(Glu)(Phn)]H₂O⁻ showing strong π-π* transitions at 235 nm. The complexes [Fe(Glu)(Phn)(H₂O)₂], [Mn(Glu)(Phn)(H₂O)₂]⁻, and [Cu(Glu)(Phn)]H₂O⁻ demonstrated broader absorptions with transitions corresponding to ⁶A₁g → ⁴T₁g, LMCT, and ⁴A₂g → ⁴T₂g, respectively. Significant shifts in absorption bands, specifically C=O stretching (1750-1600 cm⁻¹ to 2373-2297 cm⁻¹) and NH₂ bands (2900 cm⁻¹ to 3200 cm⁻¹), indicated metal-ligand coordination through O and N donor sites, which were validated by FTIR analysis. The crystalline nature of all compounds with comparable bonding patterns was demonstrated by X-ray diffraction research. According to structural and spectroscopic analyses, [Mn(Glu)(Phn)(H₂O)₂]⁻ and [Fe(Glu)(Phn)(H₂O)₂] display octahedral geometries, [Cu(Glu)(Phn)]H₂O⁻ displays square planar coordination, and [Zn(Glu)(Phn)]H₂O⁻ takes on a tetrahedral geometry.