An unusual iminoacylation of 2-amino pyridyl thiazole: Synthesis, X-ray crystallography and DFT study of copper(II) amidine complexes and their cytotoxicity, DNA binding and cleavage study

Synthesis, Structural Elucidation and Pharmacological Applications of Cu(II) Heteroleptic Carboxylates

Six heteroleptic Cu(II) carboxylates (1-6) were prepared by reacting 2-chlorophenyl acetic acid (L¹), 3-chlorophenyl acetic acid (L²), and substituted pyridine (2-cyanopyridine and 2-chlorocyanopyridine). The solid-state behavior of the complexes was described via vibrational spectroscopy (FT-IR), which revealed that the carboxylate moieties adopted different coordination modes around the Cu(II) center. A paddlewheel dinuclear structure with distorted square pyramidal geometry was elucidated from the crystal data for complexes 2 and 5 with substituted pyridine moieties at the axial positions. The presence of irreversible metal-centered oxidation reduction peaks confirms the electroactive nature of the complexes. A relatively higher binding affinity was observed for the interaction of SS-DNA with complexes 2-6 compared to L¹ and L². The findings of the DNA interaction study indicate an intercalative mode of interaction. The maximum inhibition against acetylcholinesterase enzyme was caused for complex 2 (IC₅₀ = 2 µg/mL) compared to the standard drug Glutamine (IC₅₀ = 2.10 µg/mL) while the maximum inhibition was found for butyrylcholinesterase enzyme by complex 4 (IC₅₀ = 3 µg/mL) compared to the standard drug Glutamine (IC₅₀ = 3.40 µg/mL). The findings of the enzymatic activity suggest that the under study compounds have potential for curing of Alzheimer's disease. Similarly, complexes 2 and 4 possess the maximum inhibition as revealed from the free radical scavenging activity performed against DPPH and H₂O₂.

Evaluation of the anticancer activities with various ligand substituents in Co(II/III)-picolyl phenolate derivatives: synthesis, characterization, DFT, DNA cleavage, and molecular docking studies

The reactions between 2-(pyridine-2-ylmethoxy)-benzaldehyde (L) and various primary amines furnish tridentate (L1 to L3) and tetradentate (L4) chelating ligands. The choice of different primary amines in the condensation reaction incorporates the chiral carbon atom in L2 and L3. A series of mononuclear cobalt(II) complexes, [CoII(L1)(Cl)2] (1), [CoII(L2)(Cl)2]·CH3CN (2), [CoII(L3)(Cl)2] (3), and [CoIII(L4)(N3)2] (4) are synthesized in the pure crystalline state from the resulting solution of cobalt(II) chloride and/or azide and respective ligand. The new ligands and cobalt complexes are characterized using spectral (UV-Vis, 1H-NMR, IR, and HRMS), cyclovoltammetric, and DFT studies. The structure of L1, L2, and all four cobalt complexes are determined by single X-ray crystallography. Cytotoxic activity of the compounds is evaluated using three different tissues of origin e.g., U-937 (histiocytic lymphoma), HEK293T (embryonic kidney), and A549 (lung carcinoma). The cobalt complexes are more active than the corresponding ligands against U-937 and HEK293T. The MTT assay demonstrates that the cobalt compounds are more effective anticancer agents against U-937 cancer cells than HEK293T and A549. The toxicity order, 1 (7.2 ± 0.3 μM) > 3 (11.4 ± 0.6 μM) > 2 (12 ± 0.1 μM) > 4 (29 ± 1 μM) is observed against U-937 cancer cells. All the compounds induce cell death through an apoptosis mechanism and all are ineffective against PBMCs. The mechanism of activity against U937 cancer cells involves caspase-3 activation and two different mitogen-activated protein kinases attesting the programmed cell death. Among the compounds, complexes 1, 2, and 3 show DNA cleavage activity both in oxidizing (H2O2) and reducing (GSH) environments. The mechanistic study reveals that singlet oxygen (1O2) is the major species involved in DNA cleavage. The absolute chemical hardness values of the ligands and 4 are relatively higher than 1, 2, and 3, which tacitly support the DNA cleavage experiment. The docking result indicates that the compounds under investigation strongly interact with DNA base pairs through a variety of interactions which attests successfully to the experimental results. A structure-activity relationship has been drawn to correlate the variation of antitumor activity with ligand conformations.

Anticancer activity, DNA binding and docking study of M(ii)-complexes (M = Zn, Cu and Ni) derived from a new pyrazine–thiazole ligand: synthesis, structure and DFT

A series of structurally related Zn(ii), Cu(ii) and Ni(ii) complexes of 4-(2-(2-(1-(pyrazin-2-yl)ethylidene)hydrazinyl)-thiazol-4-yl)-benzonitrile (PyztbH) have been synthesized and characterized by spectroscopy, single crystal X-ray crystallography and density functional theory (DFT).