Halogen-containing NHC and bis-NHC silver complexes. Synthesis, structure and antimicrobial activity

It was found that the in-situ reaction of halogen-containing imidazolium and benzimidazolium salts with silver nitrate, chloride, iodide or perchlorate in the presence of potassium carbonate leads to the corresponding carbene (LAgX) and biscarbene complexes of silver (L 2 AgX) including the first strongly sterically shielded biscarbene complexes (IPr) 2 AgX. In the presence of o-phenanthroline, carbene-phenanthroline complex (IPr*)(phen)AgClO 4 was obtained. The reactions can be an addition to the known method of Lin with the use of silver oxide. The halogenide silver carbene complexes are also obtained by the exchange of the anion from the ionic perchlorate complexes to halogenide ions (Cl - , I - ). The structure of the synthesized compounds is confirmed by the methods of 1 H and 13 C NMR spectroscopy and for five compounds by the X-ray diffraction study. Most compounds have an ionic character in crystals and in solutions, even for the complex with a sterically shielded silver atom (IPr) 2 AgNO 3 and monocarbene complexes. Synthesized complexes show high antibacterial (MIC up to 1.9 μg/mL on M. luteum ) and antifungal activity (MIC up to 0.9 μg/mL on A. niger and 1.9 μg/mL on C. tenuis ). Halogen-containing carbene and biscarbenecomplexes of silver show high antimicrobialactivity exceeding in some cases the activity ofthe known drugs. Strongly sterically shieldedcomplexes are analogs of biological systems. • Biologically active carbene complexes obtained by simple procedure • Ionic nature of most synthesized complexes • Sterically shielded complexes of silver - analogs of biological systems • High in vitro antimicrobial activity of halogen-containing silver complexes