Centrosymmetric homo- and heteroleptic core paddle-wheel copper(II) carboxylates; Syntheses, crystal structures, antioxidant, anticancer and enzyme inhibition activity

Synthesis and characterization of homo- (C ₅H ₇N ₂) ₂[Cu ₂(3,5-F ₂C ₆H ₃CH ₂COO) ₆] (1) and heteroleptic [Cu ₂(3,5-F ₂C ₆H ₃CH ₂COO) ₄(2-CH ₃Py) ₂] (2) core paddle-wheel copper(II) carboxylates is reported in the present work. The characterization was made by spectroscopic techniques, elemental and single crystal XRD analyses. The single crystal XRD analysis revealed a rare homoleptic anionic copper(II) carboxylate complex (1) consisting 2-aminopyridinium counter cations and a neutral heteroleptic copper(II) carboxylate complex (2) consisting 2-methyl pyridine as a co-ligand. The copper ions adopted a distorted square pyramidal geometry in both the paddle-wheel dimeric complexes. To evaluate the biological potency of the synthesized complexes, in vitro antioxidant, enzymes inhibition and anticancer activities were performed. The synthesized complexes have shown overall better biological activity compared to the ligand acid. Complex 2 was the most potent DPPH (IC ₅₀ =180.96 ± 9.04 µg/mL) and •OH (IC ₅₀ = 189.51 ± 9.33 µg/mL) radicals scavenger, α-amylase (IC ₅₀ = 441.86 µg/mL) and acetylcholinesterase (IC ₅₀ = 88.62 µg/mL) inhibitor. Furthermore, complex 2 activity against malignant glioma U-87 cell line (IC ₅₀ = 21.95 µg/mL) was also highest among the tested compounds. However, complex 1 with an IC ₅₀ value of 51.83 µg/mL has shown somewhat better inhibition of the butyrylcholinesterase enzyme compared to the complex 2 (IC ₅₀ = 56.36 µg/mL).