Synthesis, Spectroscopic Characterization, DFT, Drug‐Likeness, ADMET, ‏and Toxicity Predictions of Octahedral Zn(II) and Cd(II) Complexes With Tetradentate N ₂ O ₂

ABSTRACT

The octahedral complexes of the type [M(L)X ₂ ] (M = Zn, Cd; X = Cl or H ₂ O) were synthesized by complexing two tetradentate N ₂ O ₂ Schiff base ligands (L1, L2) with Zn(II) and Cd(II) ions in a 1:1 molar ratio. FT‐IR, UV–vis, C.H.N, ¹ H‐NMR, molar conductance, and elemental analysis were used to characterize the compounds. The molar conductance data (10.6–15 Ω ⁻¹ cm ² mol ⁻¹ ) showed that the complexes were non‐electrolytic, and the spectroscopic data indicated octahedral geometry for the complexes. The density functional theory (DFT) calculations showed that the HOMO–LUMO energy gaps vary from 0.01085 a.u. (L1, most reactive) to 0.11963 a.u. (L2, most stable) which suggests tunable electronic properties upon metal coordination. Based on ADMET profiling, L2 was found to be a promising candidate for central nervous system applications, having high gastrointestinal absorption and a blood–brain barrier (BBB) penetration probability of 0.95. L2 was found to be drug‐like (0.35) while L1 was found to have limited permeability (TPSA = 190.68 Å ² ) and lower scores (−1.1 to −1.25). L1 and P1 were found to be nontoxic (Class 6, LD ₅₀ up to 10,000 mg/kg) while the L2 complexes were more toxic (Class 4, LD ₅₀  = 1,000 mg/kg), indicating a balance between improved pharmaceutical properties and increased toxicity.