Ten neutral monomeric, dimeric and polymeric mercury(II) complexes of compositions HgX₂L (3, 8), [HgX₂L]₂ (1, 2, 4–6 and 7), [Hg(NO₃)₂L]_n (9) and {[Hg(N₃)₂L]₂}_n (10) where X = chloride, bromide, iodide, nitrate and azide, and L = (E)-N-(pyridin-2-ylmethylidene)arylamine, are described. Compounds 1–10 were characterized by elemental analyses, and IR and ¹H NMR spectroscopic studies. The solution-state photophysical properties of the complexes are highly dependent on the anions as seen in the fluorescence emission features. Single-crystal X-ray crystallography showed that the molecular complexes can aggregate into larger entities depending upon the anion coordinated to the metal centre. Iodide gives discrete monomeric complexes, chloride and bromide generate binuclear complexes formed through Hg–X–Hg bridges, while nitrate and azide lead to 1D coordination polymers. The significant differences in the observed aggregation patterns of the compounds indicate that the anions exert a substantial influence on the formation of the compounds. A further influence upon supramolecular aggregation is the presence of methyl substituents in L³ and L⁴, which generally enhances the probability of forming supramolecular π⋯π interactions involving the five-membered C₂N₂Hg chelate rings in their crystal structures.

Metal complexes with organelle specificity and potent but selective cytotoxicity are highly desirable. A novel series of triphenylstannyl 4-((arylimino)methyl)benzoates (2–8) were obtained by the reactions of triphenylstannyl 4-formylbenzoate [Ph₃Sn(L¹)] 1 with primary aromatic amines. Two representative compounds (10, 11) were also synthesized by reacting aqua-triphenylstannyl 2-formylbenzoate [Ph₃Sn(L⁹)(H₂O)] (9) with aniline and p-fluoroaniline, respectively. These compounds were characterized by elemental analysis, IR and ¹H, ¹³C and ¹¹⁹Sn NMR spectroscopy, as well as single-crystal X-ray diffraction for compounds 5, 7–11 and three pro-ligands. The in vitro cytotoxic activities of 1–11 were assessed using the MTT tetrazolium dye assay against HeLa (human cervical) and MDA-MB-231 (breast) cancer cells, with IC₅₀ values revealing high activity. Compared to cisplatin, compounds 1–11 exhibited enhanced cytotoxic efficacy, indicating their potential as potent anticancer agents. Among these, 1 and 5 demonstrated maximum inhibition in HeLa cells, with negligible effect on normal human embryonic kidney (HEK) cells. The combined results of the DCFH-DA dye and Hoechst 33342/PI nuclear staining assays, along with flow cytometry analysis, show that they possess a dual mode of action: They induced apoptotic cell death, attributable to the tin-assisted generation of reactive oxygen species. Cell cycle analyses indicated that compounds 1 and 5 exhibit cell growth inhibition and may cause turbulences in the G1 and G2/M phases.

The synthesis and spectroscopic properties of nine water soluble zinc(II) complexes of (E)-N-(pyridin-2-ylmethylene)arylamines (Lⁿ) with the general formula [Zn(X)₂(Lⁿ)] (X = Cl⁻, Br⁻, I⁻; (1–8)) and [Zn(μ-N₃)(N₃)(L³)]₂ (9) are reported. The complexes were characterized by elemental analysis and their spectroscopic properties were studied using UV-Visible, fluorescence, IR and ¹H NMR spectroscopies. The solid state structures of zinc(II) complexes 2–4 and 6–9 were established by single crystal X-ray crystallography. The majority of the structures are mononuclear with tetra-coordinate zinc centres (2–4, 6 and 7) except where L carries an additional donor atom capable of coordinating zinc (8), in which case the zinc atom has a distorted square pyramidal geometry. The centrosymmetric molecule of [Zn(μ-N₃)(N₃)(L³)]₂ (9) is binuclear with the zinc atoms in a trigonal bipyramidal coordination environment. In general, the dichlorozinc derivatives 1, 3–5 and 8 exhibited moderately elevated in vitro cytotoxic potency towards the human epithelial cervical carcinoma (HeLa) cell line, with 4 as the best performer (IC₅₀ value of 18 μM). Apoptosis-inducing activity, assessed by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, showed that the zinc complexes interacted with DNA and thereby interfered the DNA binding of several transcription factors to its promoter sites, thus inhibiting gene transcription required for the biological activity of cells.