Three luminescent mixed ligand diorganotin(IV) complexes
[Sn2Ph4(L)1–3(DPA)(MeOH)Cl]
(where
L1 = (Z)-N-((E)-3-ethoxy-2-hydroxybenzylidene)isonicotinohydrazonic acid,
L2 = (Z)-N-((E)-5-bromo-2-hydroxybenzylidene)isonicotinohydrazonic acid,
L3 = (Z)-N-((E)-2-hydroxy-3-methoxybenzylidene)isonicotinohydrazonic
acid, and DPA = dipicolinic acid) (1–3) were synthesized
and characterized physiochemically along with the single-crystal X-ray
diffraction analysis of 1 and 3. Aqueous
phase stabilities of the complexes were performed with UV–vis
and 1H nuclear magnetic resonance, suggesting that they
are stable in aqueous/biological media. The interaction of 1–3 with DNA was evaluated through analytical methods, which supported
the intercalation mode of binding. Also, the interaction of complexes
with bovine serum albumin was evaluated with fluorescence quenching
experiments showing static quenching. In addition, the results of
partition coefficients and cellular uptake suggest that the complexes
are hydrophobic and can easily enter the cells. Cytotoxic potential
of 1–3 was evaluated against HeLa, HT-29 (cancerous),
and NIH-3T3 (normal) cell lines. Complex 2 is the most
cytotoxic of the series having IC50 4.2 ± 0.7 μM
against HeLa cells. Furthermore, all the complexes showed an apoptotic
cell death confirmed by acridine orange/ethidium bromide, cell cycle
analysis, and Annexin V-FITC/PI double staining assays. Finally, by
using live cell confocal microscopy, it was found that the compounds
target the mitochondria of cancer cells and raise the reactive oxygen
species level.