Polymorphism, Spectroscopic, DFT and Anticancer Activity of a Palladium(II) Complex with a Thiophenyl Azoimine-Quinoline SNN’N” Ligand

Abstract Two polymorphs based on a new Pd(II) complex, [Pd(Y)] {H2Y = (2-SR)C6H4NHN=C(COCH3)-NHC9H6N; R=C6H5}, have been characterized by FTIR, UV/Vis, elemental analysis and 1HNMR. Quantum theory of atoms in molecules was used to analyse the bonding in the two polymorphs. The formation of different polymorphs of [Pd(Y)] was rationalized based on the chirality of the complex. The molecular structures of the two polymorphs are stabilized by C-H…O hydrogen bonding interactions. The UV/Vis spectra were calculated using time-dependent density functional theory (TD-DFT). The cytotoxic activity of the ligand and its complex were evaluated against seven cancer cell lines and one normal skin fibroblast cell line. The complex is more active against DU145, MCF7, MDA231 and HCT116 cell lines, with IC50 values in the range 0.14-0.58 μM, whereas it is less active against A375, A549 and PanC-1 cell lines, with IC50 values in the range 7.05-10.2 μM. Except for PanC-1, the ligand is also active against six cell lines, with higher IC50 values that range from 57.3-866.5 μM. The potencies of the [Pd(Y)] complex against DU145, MCF7, MDA231, and HCT116 cell lines ranged from two to elevenfold more than the potent chemotherapeutic control doxorubicin but are comparative or less for the other cell lines. The complex has shown high safety against normal cell lines compared to doxorubicin.