The present study describes the metal chelating ability of 3-hydroxyflavene, deferiprone and maltol with Ni2+ metal ion using density functional theory. Structural analysis indicates that all three chelators bind to Ni2+ ion as a two dentate chelator. Donor-acceptor interactions show an effective charge transfer from the oxygen atoms of the chelators towards Ni2+. Quantum theory of atoms in molecules analysis shows that the non-covalent interactions, mainly, electrostatic interactions play an important role in the complex formation of the selected chelators and Ni2+ ion. The TD-DFT study was applied in order to investigate the main electron transition. The ELF and LOL analyses were applied to confirm the results obtained from the QTAIM analysis. Interaction energies and metal ion affinity were calculated for the [Ni(L)2] complexes and the results revealed a highly exothermic reaction during the chelation process. The natural bond analysis (NBO), natural population analysis (NPA) and spin density evaluation were carried out to evaluate the charge transfer in the complexes. The NCI-RDG isosurface of the studied complexes show a complete set of electrostatic interactions including Van der Waals interactions. On the basis of the results, the selected chelators could be considered as the effective chelating agents for Ni therapy.

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