Cu(ii), Ga(iii) and In(iii) complexes of 2-acetylpyridine N (4)-phenylthiosemicarbazone: synthesis, spectral characterization and biological activities.

In this paper, synthesis and characterization of metal complexes [Cu ₂ (L) ₃ ]ClO ₄ ( 1 ), [Ga(L) ₂ ]NO ₃ ·2H ₂ O ( 2 ) and [In(L) ₂ ]NO ₃ ·H ₂ O ( 3 ) (HL = 2-acetylpyridine N (4)-phenylthiosemicarbazone) was carried out, including elemental analysis, spectral analysis (IR, UV-vis, NMR), and X-ray crystallography. Complex 1 contains one S-bridged binuclear [Cu ₂ (L) ₃ ] ⁺ unit, where two Cu atoms display diverse coordination geometries: one being square planar geometry and the other octahedral geometry. Both 2 and 3 are mononuclear complexes, and the metal centers in 2 and 3 are chelated by two NNS tridentate ligands possessing a distorted octahedral geometry. Biological studies show that all the complexes possess a wide spectrum of modest to effective antibacterial activities and remarkable cytotoxicities against HepG2 cells, and 1 , in particular, with an IC ₅₀ value of 0.19 ± 0.06 μM, is 113-fold and 28-fold more cytotoxic than HL and the antitumor drug mitoxantrone, respectively. In addition, 3 exhibits excellent photoluminescence properties. Upon the addition of 1 equiv of In ³⁺ ions, a remarkable fluorescence intensity of HL and fluorescent color change (from transparent to light-green) could be observed with 365 nm light, indicating that this ligand may be used as a promising colorimetric and fluorescent probe for In ³⁺ detection.