Herein, we report facile procedures for synthesis of a new Schiff base ligand (H₂L,5-Diethylamino-2-({2-[(2-hydroxy-benzylidene)-amino]-phenylimino}-methyl)-phenol) and its Ag(I), Pd(II) and Cu(II) complexes. The structure of the H₂L ligand as well as its metal complexes was deduced based on wide range of analytical, structural and spectroscopic tools, along with theoretical evidence via density functional theory (DFT) calculations. The obtained results indicated that the Schiff base (H₂L) ligand acts as a tetradentate N₂O₂ donor with two azomethine nitrogen’s (N1, N2) and two deprotonated phenolic oxygens (O1, O2) atoms. A distorted octahedral structure is assigned to [CuL(OH₂)₂]·3/2H₂O complex and square planar structure for PdL and AgL complexes. The electronic structure and non-linear optical (NLO) property of the prepared compounds were discussed theoretically by the B3LYP/GENECP program. Results revealed that all complexes have non-planner geometries as indicated from the dihedral angles. The charge transfer occurs within the synthesized complexes as indicated from the calculated energy gap between HOMO and LUMO energies. The H₂L ligand and its complexes are excellent candidates for NLO materials as implied from their hyperpolarizabilities and polarizabilities values. The biological activities of the prepared complexes against selected microorganisms and cancer cell lines gave good growth inhibitory effect. The biocidal potencies of the ligand and its complexes can be arranged as follows: AgL > CuL > PdL > H₂L, as compared to the used standard drugs. The antiproliferative activity of the studied complexes against different carcinoma cell lines such as liver (Hep-G2), breast (MCF-7) and colon (HCT-116) followed the order H₂L < AgL< PdL < CuL < vinblastine. Probing the binding interactions of prepared complexes with calf thymus (CT)-DNA using electronic absorption, gel electrophoresis and viscosity measurements revealed strong interaction via intercalation modes, as also evidenced by their molecular docking study.

Structural features and catalytic activities of five ternary copper (II)-Schiff base complexes are investigated. The ligands are derived from 3-methoxysalicylaldehyde (MS) or 4-diethylaminosalicylaldehyde (DS) and amino acids {L-phenylalanine (Phe), L histidine (His) or DL-tryptophan (Trp)}, as primary ligands, and 2,4′-bipyridyl (DP) as a secondary ligand. Cu(II)-complexes are characterized by various physicochemical tools. The catalytic efficiency of Cu(II)-complexes is studied in the oxidation of benzyl alcohol by an aqueous H₂O₂ in different reaction conditions. Temperature and catalyst features are involved in order to obtain the optimized catalytic oxidation conditions of benzaldehyde production. The Schiff base ligands and their ternary complexes are screened for their antimicrobial activities in various types of fungi and bacteria. The interaction between Cu(II)-complexes and (CT-DNA) was examined by employing various techniques, including viscosity, spectral and gel electrophoreses studies.