Design, synthesis, structural characterization, and biological evaluation of dimeric mercury(II) complexes of phosphorus ylides with terminal azide ligands

Abstract

The present study investigates the reactivity of α-keto stabilized phosphorus ylide Ph₃P=C(H)C(O)Ph(p-NO₂) (Y) with mercury(II) halides in the presence of sodium azide. The resulting dimeric mercury(II) halide complexes were characterized by elemental analysis, IR and NMR (³¹P, ¹H, ¹³C) spectroscopic methods. The structures of the complexes 0.878[(Y)Hg(N₃)(µ-Cl)]₂.0.122[(Y)Hg(Cl)(µ-Cl)]₂ (1), [Hg(µ-I)(I)(Y)]₂ (3) and [Hg(µ-Cl)(Cl)(Y)]₂ (4) were determined by single crystal X-ray analysis. The results show that the ligand Y reacts with HgCl₂ and NaN₃ in methanol to form complex 1, in which the azide acts as the terminal monodentate ligand. The use of HgX₂ (X = Br (2) and I (3)) instead of HgCl₂ under similar conditions resulted in the formation of bromide and iodide mercury(II) complexes that did not incorporate azide anions, as well as the crystal structure of 3 revealed that this complex had been previously characterized. Furthermore, the antibacterial and antifungal activities of ligand Y, complexes 1 and 4 were evaluated using macro broth dilution method against Gram-positive and Gram-negative bacteria and two fungi. In this regard, the effect of azide co-ligand on the biological properties of theses complexes was also analyzed. Complex 1 exhibited the strongest antibacterial activity, especially against Gram-negative bacteria, displaying bactericidal effects. In comparison, complex 4 required higher concentrations to inhibit Gram-negative bacteria than the complex 1. The ligand demonstrated no bactericidal activity and had a much higher MIC compared to the complexes. Both complexes inhibited fungal growth, while the ligand displayed no antifungal activity.