Novel nickel(II), palladium(II), and platinum(II) complexes having a pyrrolyl-iminophosphine (PNN) pincer: Synthesis, crystal structures, and cytotoxic activity

J Inorg Biochem. 2020 Apr:205:111015. doi: 10.1016/j.jinorgbio.2020.111015. Epub 2020 Jan 30.


A pyrrolyl-iminophosphine (PNNH) which would act as a potential terdentate ligand has been prepared by Schiff base reaction. Complexes [M(PNN)X] (M = Ni; X = Cl (1), Pd; X = Cl (2), Br (3), I (4), M = Pt; X = Cl (5)) were prepared. The title complexes were characterized by various spectroscopic (IR, 1H, 13C, and 31P NMR) and elemental analyses. The molecular structures of 1, 2, and 5 have been established by single-crystal X-ray crystallography, demonstrating a distorted square planar geometry comprising two 5-membered metallacyclic rings. Complexes 1 and 2 were found to crystallize in the orthorhombic while complex 5 crystallizes in the monoclinic. Cytotoxicities of the complexes along with PNNH were evaluated against A549 (lung), SK-OV-3 (ovarian), SM-MEL-2 (skin), and HCT15 (colon) human cancer cell lines by sulforhodamine B assay. Notably, the palladium(II) complex (2) shows the highest activity. Apoptosis activity along with the caspase inhibitor Z-VAD (Z-Val-Ala-Asp-fluoromethyl ketone) assay of 2 and 5 against A549 and HCT15 cancer cell lines were investigated to learn a mechanistic pathway for the observed cytotoxicity, practically eliminating an apoptotic cell-death route. Complexes 2 and 5 were studied to DNA cleavage assay and molecular docking simulation. The DNA (pcDNA3.0) cleavage experiment evaluates complex 5 interacting with DNA, more effectively, in comparison to complex 2. Molecular docking simulation of 2 and 5 toward DNA and GRP78 (glucose-regulated protein 78) was performed to predict binding sites of ligand-receptors and a plausible mechanistic aspect of metallodrug-action.

Keywords: Apoptosis; Cytotoxicity; DNA cleavage; Molecular docking simulation; PNN-pincer complex; X-ray crystal structure.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • A549 Cells
  • Antineoplastic Agents* / chemical synthesis
  • Antineoplastic Agents* / chemistry
  • Antineoplastic Agents* / pharmacology
  • Coordination Complexes* / chemical synthesis
  • Coordination Complexes* / chemistry
  • Coordination Complexes* / pharmacology
  • Crystallography, X-Ray
  • Cytotoxins* / chemical synthesis
  • Cytotoxins* / chemistry
  • Cytotoxins* / pharmacology
  • Endoplasmic Reticulum Chaperone BiP
  • Heterocyclic Compounds / chemistry
  • Heterocyclic Compounds / pharmacology
  • Humans
  • Molecular Docking Simulation*
  • Molecular Structure
  • Neoplasms / drug therapy*
  • Neoplasms / metabolism
  • Neoplasms / pathology
  • Nickel / chemistry
  • Nickel / pharmacology
  • Palladium / chemistry
  • Palladium / pharmacology
  • Platinum / chemistry
  • Platinum / pharmacology


  • Antineoplastic Agents
  • Coordination Complexes
  • Cytotoxins
  • Endoplasmic Reticulum Chaperone BiP
  • HSPA5 protein, human
  • Heterocyclic Compounds
  • Platinum
  • Palladium
  • Nickel