Macrocyclic [N5] transition metal complexes: synthesis, characterization and biological activities

Novel tetraaza macrocyclic Schiff base complexes of bivalent zinc: microwave-assisted green synthesis, spectroscopic characterization, density functional theory calculations, molecular docking studies, in vitro antimicrobial and anticancer activities

In the present manuscript, novel macrocyclic Schiff base complexes [Zn(N4MacL1)Cl2-Zn(N4MacL3)Cl2] were synthesized by the reaction of ZnCl2 and macrocyclic ligands (N4MacL1-N4MacL3) derived from diketone and diamines under microwave irradiation method and conventional method. The structures of the obtained complexes were identified by various spectrometric methods such as Fourier transformation infra-red (FT-IR), nuclear magnetic resonance (NMR), high-resolution mass spectrometry (HR-MS), powder X-ray diffraction, molar conductivity, and UV-vis. The structures of the synthesized compounds were optimized by using the def2-TZV/J and def2-SVP/J Coulomb fitting basis sets at B3LYP level in density functional theory (DFT) calculations. The macrocyclic Schiff base complexes exhibited higher activities against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus), Gram-negative bacteria (Escherichia coli and Xanthomonas campestris), and fungal strains (Fusarium oxysporum and Candida albicans) in comparison to macrocyclic Schiff base ligands. Furthermore, the newly synthesized macrocyclic compounds were assessed for their anticancer activity against three cell lines: A549 (human alveolar adenocarcinoma epithelial cell line), HT-29 (human colorectal adenocarcinoma cell line), and MCF-7 (human breast adenocarcinoma cell line) using the MTT assay. The obtained results showed that the macrocyclic complex [Zn(N4MacL3)Cl2] displayed the highest cytotoxic activity (2.23 ± 0.25 µM, 6.53 ± 0.28 µM, and 7.40 ± 0.45 µM for A549, HT-29, and MCF-7 cancer cell lines, respectively). Additionally, molecular docking investigations were conducted to elucidate potential molecular interactions between the synthesized macrocyclic compounds and target proteins. The results revealed a consistent agreement between the docking calculations and the experimental data.

Molecular docking, theoretical calculations, synthesis of Ru(III), Pd(II) and VO(II) complexes and activity determination as antibacterial and antioxidant

Molecular modeling calculations were used to validate 3D structures of new complexes of Ru(III), Pd(II) and VO(II) ions chelated with (E)-2-(phenylamino)-N-(pyridine-2-yl)methylene)acetohydrazide ligand. Furthermore, the calculations were used to estimate selected electronic chemical descriptors which are responsible for the biological activity. The first insight of the compound activity as antibacterial was evaluated by molecular docking analysis. The titled models showed stable binding towards lanosterol 14 alpha-demethylase (CYP51) enzyme of E. coli, indicating their inhibition effect toward bacterial growth. Structural study of the ligand and Ru(III), Pd(II) and VO(II) chelates was done using elemental analysis, FT-IR, 1H-NMR techniques. Furthermore, complexes were physically investigated based on magnetic moment, molar conductance, electronic spectroscopic and thermal analysis techniques. The antibacterial study of the synthesized compounds screened against both Gram-positive and Gram-negative bacteria revealed that these compounds display remarkable antibacterial activity and can be used as therapeutic drugs for pathogenic bacterial diseases. All complexes and ligand showed good scavenging activities which indicate a promising result for their applications as antioxidants.

Influences of γ-ray irradiation on physico-chemical, structural, X-ray diffraction, thermal and antimicrobial activity of some γ-irradiated N',N'''-((Z)-ethane-1,2-diylidine)bis(2-aminobenzohydrazide) metal complexes

A series of Co(II), Ni(II), Cu(II), Th(IV) and UO₂(II) complexes have been synthesized from reaction of nitrogen based ligand (L) i.e. N',N'''-((Z)-ethane-1,2-diylidine)bis(2-aminobenzohydrazide)(L) with their salts. Investigation of synthesized metal complexes was achieved by using elemental analyses, magnetic moment, molar conductance, FT-IR, UV/Vis. spectroscopy, thermal techniques and 3D molecular modeling. An octahedral geometry has been suggested for all complexes except for Ni(II) complex (2) which adopted tetrahedral geometry. To through a light on the probability of structure changes with γ-irradiation, the effect of gamma irradiation on powder samples of the complexes [Co(L)Cl₂].4H₂O (1); [Ni₂(L)(OAc)₄].5H₂O (2) and [Cu(L)Br₂].5H₂O (3) was investigated after being exposed to high energetic γ-rays at 100 kGy dose (hereafter referred to as (1A,2A,3A, respectively). Spectral, thermal, magnetic susceptibility, molar conductance and powder X-ray diffraction patterns (XRD) were performed before and after irradiation. In addition, the in vitro antimicrobial activity of the complexes against Staphylococcus aureus as Gram-positive strain, Escherichia coli as Gram-negative strain and antifungal Candida albicans was performed for both unirradiated and irradiated samples. The obtained results showed that the irradiated complexes were affected, but not greatly by the applied γ-irradiation dose.

Spectroscopic, SOD, anticancer, antimicrobial, molecular docking and DNA binding properties of bioactive VO(IV), Cu(II), Zn(II), Co(II), Mn(II) and Ni(II) complexes obtained from 3-(2-hydroxy-3-methoxybenzylidene)pentane-2,4-dione

Novel macrocyclic Schiff base complexes [[ML]X; where M = Cu(II), Co(II), Ni(II), Zn(II), Mn(II) and VO(IV)^; L = macrocyclic ligand; X = Cl₂ and SO₄^2-] have been synthesized and characterized by microanalytical, ¹H, ¹³C NMR, IR, Mass, UV-Vis, EPR spectral studies, as well as conductivity data. All the complexes exhibit square-planar geometry except vanadium complex. Magnetic susceptibility measurements and high conductance data reveal the monomeric and electrolytic nature of the complexes. Electronic absorption, cyclic voltammetry, viscosity measurements have been carried out on the interaction of the complexes with DNA. The results suggest that the complexes bind to DNA by intercalation via the aromatic ring of the macrocycle into the base pairs of DNA. Using gel electrophoresis experiment in the presence and absence of oxidant (H₂O₂) the nuclease cleavage activity of the complexes has been performed on plasmid DNA. The results demonstrate that most of the complexes have promising superoxide dismutase (SOD)-mimetic activity. The in vitro cytotoxicity of ligand and its complexes has also been evaluated against human breast and colon carcinoma cells. Binding interactions and energies of ligand and its metal complexes [ML]²⁺ (M = VO(IV), Mn(II), Co(II), Ni(II), Cu(II), Zn(II)) against the receptors EGFR and HER2 are performed using the Auto dock module. Consequently, it is found that the ligand is strong inhibitor for EGFR and HER2 while [VOL]SO₄ is good inhibitor for EGFR and [ZnL]Cl₂ is moderate inhibitor for HER2. The antimicrobial activity of the ligand and its complexes against bacteria Salmonella typhi, Staphylococcus aureus, Escherichia coli and Bacillus subtilis and fungi Aspergillus niger, Aspergillus flavus, Candida Albicans and Rhizoctonia bataicola. The complexes have higher activities than the macrocyclic free Schiff base. Interaction of [VOL]SO₄ to the binding sites of target protein EGFR (PDB ID: 4HJ0). Research HighlightsMacrocyclic Schiff base and its metal complexes were synthesized.Complexes bind to DNA by intercalation via the aromatic ring of the macrocycle into the base pairs of DNA.Vanadyl complex is a good inhibitor for EGFR.The complexes of copper, zinc and vanadium show efficient antitumor activity.Copper and vanadium complexes have superior antimicrobial activity than the standards.

Aromatic and heteroaromatic azacrown compounds: advantages and disadvantages of rigid macrocyclic ligands

Current approaches to the synthesis of aromatic and heteroaromatic azamacrocycles and their derivatives are summarized and systematized. The relationship between the structure of azacrown compounds and their complexation behaviour towards metal cations is analyzed. The diversity of practical applications of azamacrocyclic derivatives in medicine, biology and analytical and organic chemistry, as well as for the design of molecular devices is demonstrated.

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Synthesis, characterization and biochemical behaviour of macrocyclic complexes of Zn(II) and Co(II) metals

A series of Zn(II) and Co(II) complexes have been synthesized by template condensation of bis(benzil)-4-chloro-1,2-phenylenediamine and bis(benzil)-4-fluoro-1,2-phenylenediamine, respectively, with 4-chloro-1,2-phenylenediamine and 4-fluoro-1,2-phenylenediamine in the presence of transition metal chlorides. The complexes have been characterized by physicochemical and spectroscopic techniques. Based on these studies, an octahedral geometry has been proposed around the metal ions. The newly synthesized ligands and their metal complexes have been screened for antimicrobial and anticancer activities. The in vitro cytotoxicity towards the HeLa cell line has been evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay.