Synthesis, Ligating Properties, Thermal Behavior, Computational and Biological Studies of Some Azo-transition Metal Complexes

Abstract Synthesis of new Fe(III), Co(II), Ni(II), and Cu(II) complexes of two azo ligands; 1-(phenyldiazenyl) naphthalene-2-ol (sudan orange R, HL1), and sodium 2-hydroxy-5-[(E)-(4-nitrophenyl) diazenyl]benzoate (alizarin yellow GG, HL2) have been reported. Stoichiometries of 1:2 and 1:3 (M:L) of the synthesized complexes were approved by total-reflection X-ray fluorescence technique (TXRF) and by elemental analyses. Complexes geometry of octahedral and square planar types were characterized by various spectroscopic, thermal, and magnetic moment measurements. Notably, bidentate coordination was the common binding mode of the ligands under investigation. The ESR spectroscopy showed that Cu(II) complexes are of different isotropic and rhombic symmetries accompanied by the existence of Cu-Cu ions interaction. TGA, DTA and DSC techniques supported the multi-stage thermal decomposition mechanisms, where the thermal breakdown is ended by the formation of metal oxide in most cases. Moreover, optimization of the structure and chemical reactivity modeling using the density functional theory (DFT) method with the B3LYP/6–31 basis set, showed that metal complexes are more biologically active than their precursor ligands. The calculated lipophilicity character for metal complexes is in the range 33.8–37.5 eV. Furthermore, nucleophilic and electrophilic regions on the surface of the ligands have been mapped aiming to prove the preferable sites of interaction with the metal ions. Docking results revealed high scoring energy for [Fe(HL2)3].H2O complex and moderate inhibition strength of [Cu(L1)2].H2O complex versus 1bqb, 3t88 and 4esw proteins. Ultimately, the extent of biological effectiveness was endorsed experimentally against four microbial strains. The results are guidelines for toxicological investigations.