Sonochemical synthesis of highly luminescent silver complexes: Photophysical properties and preliminary in vitro antitumor and antibacterial assays

Novel mononuclear silver(I) complexes based on thiocarbamoyl-pyrazoline ligands were synthesized and structurally characterized. Complexes 1 and 2 were prepared in good yields using a sonochemical method. X-ray diffraction studies revealed trigonal coordination geometry for the Ag-I atom in complex 1 and distorted trigonal pyramidal geometry in complex 2, according to tau(4) parameter analysis. Investigation of photophysical properties revealed intense blue-greenish emissions both in solution and in the solid state when excited at 300 nm. This emission was tentatively attributed to mixed (M + X)LCT and IL electronic transitions taking place after ligand metalation, as shown by DFT calculations. Complete characterization of the prepared compounds was also performed, including H-1 and C-13 NMR experiments, elemental analysis, infrared spectroscopy, absorption/emission studies, and time-resolved luminescence experiments. The synthesized ligands and complexes 1 and 2 were also tested as antibacterial agents against two standard bacterial strains (Staphylococcus aureus ATCC 25923 and Escherichia coli ATCC 25922) and a panel of clinical S. aureus strains with distinct antibiotic-resistance profiles. Antitumor activity was investigated against melanoma cells (B16F10) and mammary carcinoma cells (4T1).