Synthesis, Characterisation and Spectral Studies of Mixed Transition Metal Complexes of L-aspartic and L-glutamic Acids

Mixed-aminocarboxylato complexes of L-aspartic acid (Asp) and L-glutamic acid (Glu) with Fe(III), Mn(II), Cu(II) and Zn(II) have been synthesized by solvothermal methods. Results from their characterization showed the electrolytic nature of the complex ions in dimethyl sulphoxide solutions, with conductivity values (175.13 –34.35) Ω-1 mol-1 cm2 for the respective complexes. Furthermore, μeff measurements suggested that all complexes were paramagnetic, except [Zn(Asp)(Glu)] 2-.H2O which was diamagnetic. FT-IR spectral data gave important bands at (3578 – 3416) cm-1; present in all complex ions but absent in Asp and Glu spectra, signifying the presence of -OH vibrations from H2O molecules. Subsequent bands shift suggestive of –NH2, C-N, C=O and COO– were observed as evidences of metal-ligands interactions in all complex ions. UV-visible studies gave λmax values for [Fe(Asp)(Glu)(H2O)2]– (457 nm), [Mn(Asp)(Glu)(H2O)2]2– (235 nm), [Zn(Asp)(Glu)]2-.H2O (191 nm) and [Cu(Asp)(Glu)]2-.H2O (590 nm), with transitions assigned accordingly. Similar bonding modes in all complexes were predicted as Powdered XRD analysis gave similar crystallite sizes for all complex ions. Evidences exists that both Asp and Glu act as bidendate ligands with the O-carboxylic and N-amine donor atoms as active sites. The predicted geometry for [Fe(Asp)(Glu)(H2O)2]– and [Mn(Asp)(Glu)(H2O)2]2– is octahedral, [Zn(Asp)(Glu)]2–.H2O is tetrahedral while [Cu(Asp)(Glu)]2–.H2O is square planer respectively.