Introducing N‐Heteroaromatic Bases into Copper(II) Thiosemicarbazon Complexes: A Way to Change their Biological Activity

Abstract

Three new copper(II) complexes, [Cu(1,10-Phen)(L)] (1), [Cu(2,2'-Bpy)(L)] ( 2) and [Cu(3,,10-Phen = 1,10-phenanthroline, 2,2'-Bpy = 2,2'-bipyridine, 3,4-Lut = 3,4-lutidine, have been synthesized and characterized by elemental analysis, FTIR spectroscopy and single crystal X-ray crystallography (1, 2). All compounds are mononuclear. The introduction of a monodentate N-heteroaromatic base (3,4-dimethylpyridine) has led to a significant increase of antimicrobial activity against Gram-negative Escherichia coli and antifungal activity against Candida albicans compared to the pro-ligand and the precursor complex [Cu-(L)H 2 O]. The introduction of bidentate N-heteroaromatic bases did not lead to such increase of antimicrobial and antifungal activities. Moreover, complex 3 surpasses the inhibitory activity of tetracycline toward Enterobacter cloacae and the inhibitory activity of fluconazole toward Candida parapsilosis and Cryptococcus neoformans. The study of antioxidant activity against cation radicals ABTS * + showed that complexes 1-3 are more active than Trolox, but only introduction of the monodentate Nheteroaromatic base (3,4-dimethylpyridine) led to the increase of antioxidant properties compared to the precursor complex.

A new thiosemicarbazone and its 3d metal complexes: Synthetic, structural, and antioxidant studies

“…In the literature, cases of similar systems with thiosemicarbazones are described, in which introducing a bidentate N -heteroaromatic base into the inner sphere of copper(II) complexes also did not lead to an increase in antioxidant activity. 27 The antioxidant activity of coordination compounds is influenced by the nature of the central atom, and the activity decreases in the following order: Fe 3+ > Cu 2+ > Ni 2+ . In the literature, there are numerous cases where copper complexes are identified as the most active antioxidants toward ABTS +• cation radicals.…”

“…23 Thiosemicarbazones and their coordination compounds manifest antioxidant activity, often exhibiting values that exceed the activity of medicines used as antioxidants. [24][25][26][27] Studies of the antioxidant activity of pyruvic acid have shown that it has potential for controlling inflammation and preventing diseases caused by oxidative stress. 28 The aim of the present investigation is the synthesis of 1) and its 3d metal coordination compounds, which include bidentate N-heteroaromatic bases such as 1,10-phenanthroline (1,10-Phen) and 2,2′-bipyridine (2,2′-Bpy), along with studies of the antioxidant activities.…”

“…23 Thiosemicarbazones and their coordination compounds manifest antioxidant activity, often exhibiting values that exceed the activity of medicines used as antioxidants. 24–27 Studies of the antioxidant activity of pyruvic acid have shown that it has potential for controlling inflammation and preventing diseases caused by oxidative stress. 28…”

Synthesis, Characterization, and Biological Properties of the Copper(II) Complexes with Novel Ligand: N-[4-({2-[1-(pyridin-2-yl)ethylidene]hydrazinecarbothioyl}amino)phenyl]acetamide

“…Free radicals play a significant role in various detrimental biological processes, including protein denaturation and lipid peroxidation, contributing to the development of numerous human diseases [39,40]. Hence, investigating the antioxidant potential of the synthesized compounds becomes crucial to determine whether they can mitigate the levels of free radicals and provide protection against oxidative stress in the human body.…”

“…39. Selected FT-IR data, ν (cm −1 ): ν(NH amide II) 3154, ν(CH Aryl) 3060, ν(C=Npy) 1509, ν(C-S) 675, the full spectrum is shown in FigureS4.…”