Synthesis and Characterization of Neutral Cyclometalated Platinum(II) Complexes and their Antibacterial and Cytotoxic Evaluations

A series of neutral cyclometalated platinum(II) complexes bearing 2,6-bis(2-naphthyl)pyridine as a C^N^C tridentate chelating ligand with monodentate pyridyl ligands with different substituents 1–3 have been synthesized via double cyclometalation and ligand displacement reaction. The structural, photophysical, electrochemical and aggregation induced emission (AIE) properties of these neutral platinum(II) complexes were systematically studied. Complexes 1–3 exhibited AIE effects with different emission intensities and colors, in which 1 showed the highest quantum efficiency of 8.6 % under aggregated state, and the aggregates were assembled to ordered spheres. Among the Pt(II) complexes, 1 showed a bactericidal activity against both Staphylococcus aureus (S. aureus) (MIC and MBC=3.13 μg/mL) and methicillin-resistant S. aureus (MRSA) (MIC and MBC=6.25 μg/mL). Complex 1 did not possess noticeable cytotoxicity to human skin HaCaT keratinocytes. The non-cytotoxic complex 1 would have a good potential to be used for the antibacterial therapy to combat with S. aureus and MRSA-infected skin diseases.