Potentiometric, Raman spectroscopy and DFT study of pentaaqua glycine aluminum(III) complex in aqueous solution

• Glycine promotes Al3+ absorption, and aluminum glycinate salt is used as a drug.
• Complexes of the Al:Gly system were studied by potentiometry and molecular modeling.
• [Al(Gly)(H2O)5]3+ was analyzed by Raman spectroscopy and DFT calculations.
• Gly behaves as a monodentate ligand in [Al(Gly)(H2O)5]3+.
• Molecular modeling of the complex suggested a distorted octahedral structure.

Aluminum ion bioaccumulation is associated with the formation of β-amyloid peptide, a main microscopic characteristic of Alzheimer’s disease. β-amyloid affects glucose transport and consequently limits glycine synthesis. Glycine is an important amino acid in several body functions and it acts as an inhibitory neurotransmitter in the central nervous system. Moreover, aluminum glycinate salt is used as medication. The complex formed by aluminum(III) and glycine in aqueous solution at metal-to-ligand ratio of 1:1 has been studied by potentiometry, Raman spectroscopy and quantum chemical calculations (DFT:B3LYP/6-311++G**). Atomic charges, electrostatic potential contour surface, electrostatic potential map and donor–acceptor second order perturbative energies were examined. Potentiometry data revealed complexion formation. Distributions of species pointed out the better value to perform the Raman analyses. Raman data was used to confirm complexion formation and indicated coordination mode adopted by the ligand. Quantum chemical calculations provided data about structure, normal modes, charge distribution and delocalization. Glycine should act as a monodentate ligand through the oxygen of the carboxylate group in pentaaqua glycine aluminum(III). The other positions in the octahedral arrangement are occupied by coordinated water molecules.

Figure optionsDownload as PowerPoint slide