Structural and theoretical studies of iron(III) and copper(II) complexes of dianion N¹,N⁴-bis(salicylidene)-S-alkyl-thiosemicarbazide

Iron(III) and copper(II) complexes with an allyl N'-(1-(2-hydroxyphenyl)ethylidene)carbamohydrazonothioate·hydrobromide (H₂L) and ethyl N'-5‑bromo-2-hydroxybenzylidenecarbamohydrazonothioate·hydrobromide (H₂L') ligands were synthesized and characterized by elemental analysis, FT-IR spectroscopy and molar conductivity. Single crystal X-ray crystallography reveals that the iron and copper complexes have square pyramidal and square planar geometries, respectively. The ligands act as a binegative tetradentate chelating agent and they are bonded to the metal center through the phenolic oxygen, isothioamide nitrogen, and azomethine nitrogen atoms. The fifth site of the Fe(III) coordination sphere in both Fe complexes is occupied by chloride ion. Density functional theory method was used to complement the structural and spectroscopic data obtained experimentally. We also performed docking calculations of the complexes with human serum albumin and the copper complex binds preferentially.