Nickel(II) and copper(II) coordination complexes based on novel ligands generated in situ from the tetradentate 2,4-pentanedione bis(thiosemicarbazone) and the thiocyanate ion: Network topologies, and computational approaches

Abstract

The synthesis of the [Ni^II(H₂L³)]SCN 1 and [Cu^IIL⁴(SCN)]⋅2DMF 2 complexes was carried out using the proligand 1-thiocarbamoyl-3,5-dimethyl-5(thiosemicarbazido)-2-pyrazoline (H₂L²); derivative from 2,4-pentanedione bis(thiosemicarbazone) (H₃L¹), the thiocyanate ion and the divalent metal ions of nickel and copper. Complex 1 was prepared by reaction of the cyclic ligand H₂L² with a solution containing the SCN⁻, Ni²⁺ and Cu²⁺ ions. Single crystal X-ray diffraction (SC-XRD) study revealed that this complex is a cationic mononuclear complex of Ni^II with a new generated ligand (H₂L³)⁻, arising from the establishment of a bond between the nitrogen atom of the thiocyanate and the central carbon atom of the organic ligand (H₃L¹). The geometry around the nickel is square planar of MN2S2 mode, while the second thiocyanate played the role of counter-anion in the Ni(II) complex structure. With a solution containing only the thiocyanate and the cupric ions, the proligand H₂L² leads in two steps to the complex 2 which is based on an original heterocyclic ligand issue also from the reaction of thiocyanate ion with H₃L¹ ligand, but in different way. The crystallographic study revealed a new coordination sphere of square planar geometry where the new ligand (L⁴) is in tridentate mode (N2S) and a thiocyanate ion is linked in terminal mode by the nitrogen atom. In addition to XRD, the title complexes have been characterized using FTIR, UV–Vis, as well as Hirshfeld surface analysis and plausible mechanisms have been proposed to explain the in situ formation of the new ligands. Furthermore, the synthesized coordination complexes were studied by PASS, molecular docking, and in silico ADME assessments to evaluate the biological activity, molecular interactions, and pharmacokinetic properties. PASS Prediction identified enhanced antineoplastic activity in ligand–metal complexes, confirmed by molecular docking against Cyclin-dependent kinase 2 (CDK2) receptor for a xenograft cancer.