Synthesis, characterization, and theoretical studies on ylidic complexes of mercury(II) as antioxidant agents

Abstract

Herein we describe the synthesis of a library of new mercury complexes, including some dimers and polymeric species. Initially, a phosphonium salt, [PPh₃CH₂C(O)C₆H₄–m-OCH₃]Br (S), was synthesized from triphenylphosphine (PPh₃) and BrCH₂C(O)C₆H₄-m-OCH₃ in acetone. We then reacted this phosphonium salt with an appropriate base to acquire a new phosphorus ylide monodentate, PPh₃=C(H)C(O)C₆H₄-m-OCH₃ (Y). Finally, we treated the synthesized ligand with mercury halides in dry CH₃OH to form C-coordinated complexes of the form [HgX(PPh₃C(H)C(O)C₆H₄-m-OCH₃) (μ-X)]₂ [X = Cl (1), Br (2), I (3)], [(PPh₃=C(H)C(O)C₆H₄-m-OCH₃)Hg(NO₃)₂]_n (4). We characterized these compounds using CHN analysis, FT-IR, NMR (¹H, ¹³C and ³¹P) and density functional theory. We elucidated the structure of 2 by single-crystal X-ray diffraction. The results establish that 1, 2 and 3 have dimeric structures, while a polymeric structure is suggested for 4. The antioxidant activity of all compounds in DMSO was assessed using a DPPH free radical scavenging method. Also, the nature of metal-ligand (C→Hg) bonding in 1, 2 and 3 have been investigated using natural bond orbital (NBO) and energy-decomposition analyses (EDA).

KEYWORDS:

• Phosphorus ylide
• Hg complex
• antioxidant activity
• DFT
• NBO
• EDA

Acknowledgements

Funding of our research from the Bu-Ali Sina University is gratefully acknowledged.

Disclosure statement

No potential conflict of interest was reported by the authors.