Indones. J. Chem., 2021, 21 (3), 708 - 724 Ali Mahmood Ali et al. 708 Synthesis and DFT Study of the Complexation of Schiff Base Derived Curcumin and L-Tyrosine with Al(III), Ag(I), and Pb(II) Metal Ions Ali Mahmood Ali 1 , Tagreed Hashim Al-Noor 1 , Eid Abdalrazaq 2* , and Abdel Aziz Qasem Jbarah 2 1 Department of Chemistry, Ibn Al-Haithem College of Education for Pure Science, Baghdad University, Baghdad, Iraq 2 Department of Chemistry, College of Science, Al-Hussein Bin Talal University, Ma’an, Jordan * Corresponding author: tel: +962-796862267 email: eidalzooby@yahoo.com Received: December 13, 2020 Accepted: February 22, 2021 DOI: 10.22146/ijc.62188 Abstract: The multi-dentate Schiff base ligand (H2L), where H2L=2,2'-(((1,3,5,6)-1-(3- ((l1-oxidaneyl)-l5-methyl)-4-hydroxyphenyl)-7-(4-hydroxy-3-methoxyphenyl)hepta-1,6-di ene-3,5-diylidene)bis(azaneylylidene))bis(3-(4-hydroxyphenyl)propanoic acid), has been prepared from curcumin and L- Tyrosine amino acid. The synthesized Schiff base ligand (H2L) and the second ligand 1,10-phenanthroline (phen) are used to prepare the new complexes [Al(L)(phen)]Cl, K[Ag(L)(phen)] and [Pb(L)(phen)]. The synthesized compounds are characterized by magnetic susceptibility measurements, micro elemental analysis (C.H.N), mass spectrometry, molar conductance, FT-infrared, UV-visible, atomic absorption (AA), 13 C-NMR, and 1 H-NMR spectral studies. The characterization of the synthesized complexes shows that the environment surrounding the central metal ion in the complexes adopted a distorted octahedral configuration. Moreover, the conductivity measurements show a non-electrolytic character for the [Pb(L)(phen)] complex and an electrolytic character for the [Al(L)(phen)]Cl and K[Ag(L)(phen)] complexes. The experimental infrared data are supported by density functional theory (DFT) calculations using the B3LYP level of theory and LANL2DZ basis set. The vibrational frequencies of the molecules are computed using the optimized geometry obtained from the DFT calculations. The calculated vibrational frequencies have been compared with obtained experimental values. 1 H and 13 C-NMR chemical shifts were computed for the H2L ligand using the DFT/GIAO method. Additionally, the molecular electronic structures of the complexes have been investigated by DFT calculations. Keywords: curcumin; L-tyrosine; silver; aluminium; lead; Schiff base ■ INTRODUCTION Schiff base derived from curcumin has much attention due to its various medicinal properties against expanding and dangerous diseases, such as different types of cancer and diabetes. Curcumin has various biological activities includes antioxidant, anti-inflammatory, antiviral, antibacterial, and many more studies [1-2]. The curcumin Schiff base was coordinated to the metal ion due to their catalytic power and antioxidant activity of these complexes [3]. In drug design, targeting is an important phenomenon because toxicity is often encountered only if the drugs are not delivered to the specific tissues, cells, and receptors where they are required. If the active species of drugs contain metal complexes, then the complexes can spontaneously undergo biological reactions such as ligand substitution and redox reactions. Thus, enumerating the mechanism of the active species on biological reactions is expected to yield valuable information about using the metal complexes as drugs [4]. During the last few decades, metal carboxylates have been the subject of extensive investigations because of their remarkable structural diversity and significant biological activity, for example, pesticidal, bactericidal, and antitumor agents [5]. The antimicrobial activities of lead compounds of Schiff base have been compared with the corresponding free Schiff bases and standard drugs