Theoretical investigation and antineoplastic potential of Zn (II) and Pd (II) complexes of 6-methylpyridine-2-carbaldehyde-N (4)-ethylthiosemicarbazone

Abstract

Density Functional Theoretical (DFT) and molecular docking studies have been used to elucidate the antineoplastic potential of the ligand 6-Methylpyridine-2-carbaldehyde-N (4)-ethylthiosemicarbazone (MET) and its platinum(II) and zinc(II) complexes. The frontier molecular orbital and the global quantum reactivity parameters were used to study the reactivity and stability of the modeled complexes. The energy gap showed that the complexes have their reactivity in the order Pd[MET] < [MET] < Zn[MET] suggesting a higher reactivity of the Pd complex compared to its Zn(II) congener. NBO indicated Pd(MET)Cl complex to have the highest E(2) energies and exhibiting highest interaction arising from strong coordination of the thiolato sulfur and chloride atoms around the Pd2+ as seen in the σ*S21 -Pd13→ σ*Pd31 – Cl32 transition. QTAIM revealed that highest density of electrons follows the order [Pd(MET)Cl] >[Zn(MET)Cl] > [MET], while computational drug design protocols carried out provided the order of binding affinity as Pd(MET)Cl > Zn(MET)Cl and MET which again presents Pd complex as having greater antineoplastic activity. Our DFT findings are in excellent agreement with previous experimental reports thereby affirming the potential of these complexes as possible candidates for antineoplastic chemotherapeutic treatment against the human colon tumor cell lines (HCT 116) .