Synthesis, photophysical behavior and biomolecular reactivity of new triphenylphosphonium-based Pd(II)salphens as new anticancer candidates

[Display omitted] •Series of TPP-based salphens and their Pd(II) complexes were successfully prepared.•The molecular structures of these new compounds were investigated.•Binding of complexes with CT-DNA was investigated by absorption and emission spectrophotometry.•Reactivity of Pd(II) complexes with BSA was studied by UV–vis and fluorescence techniques.•In vitro cytotoxicity of new Pd(II) complexes revealed great efficacies against HepG2 cells. The synthesis of new bis-triphenylphosphonium-based dimethlysalphens (salphen = N,N`-bis-(salicylidene)-o-phenylenediimine) and their complexes (Pd(II)-salphens) for chemotherapeutic applications were reported. The in vitro anticancer efficacy of new compounds against human hepatocellular carcinoma (HepG2) cell lines demonstrated higher activity for Pd-complexes as compared with their parent ligands. Among tested compounds, Pd(II)-salphen3 was found to be the most potent one in the suppression of HepG2 proliferation (IC50 = 3.01 μM), ˜3-fold lower than the clinical drug (cisplatin, CDDP) (IC50 = 8.28 μM). The Pd(II)-salphens can effectively bind to CT-DNA via a non-covalent interaction (intercalation/ electrostatic) as revealed from the hyperchromism of 28–53% along with 3–6 nm bathochromism observed during the electronic absorption titration of Pd(II)-salphens with CT-DNA. On the other hand, the H-bonding and hydrophobic interactions play crucial roles in the binding of Pd(II)-salphens to BSA as indicating from the BSA fluorescence quenching by Pd(II) complexes. Noteworthy, Pd(II)-salphen3 displayed the highest reactivity towards DNA/ BSA with intrinsic binding constants (Kb/ KF) (3.01 × 105/ 2.95 × 106 M–1).