Experimental and theoretical analysis of molecular structure, vibrational spectra and biological properties of the new Co(II), Ni(II) and Cu(II) Schiff base metal complexes

Examining the impact of hydroxy group position on antibacterial activity of copper complexes derived from vanillin-based Schiff bases: Experimental and computational analysis

The positioning of the hydroxy group plays a crucial role in the coordination of Schiff bases with copper ions and their antibacterial effectiveness. This potential is an area of interest for future exploration, although no specific studies have been conducted. This study aims to reveal the significance of the positioning of the hydroxy group in the ability of the Schiff base to coordinate with copper ion and its antibacterial efficacy against E. coli and S. aureus. By utilizing ortho-vanillin and para-vanillin as precursors, we successfully synthesized Schiff bases HL1 (ortho) and L2 (para), which were confirmed through Fourier Transform Infrared (FT-IR) and Nuclear Magnetic Resonance (NMR) analyses. HL1 forms the CuL1 complex as a bidentate ligand with N, O donor atoms, while L2 only provides a single N donor atom, forming the CuL2 complex but retaining a free hydroxy group. Crystallographic analysis revealed a tetragonal crystal system for the Schiff base and orthorhombic for the complex. Electronic transition analysis supported by Density Functional Theory (DFT) studies indicated a distorted square plane geometry for the CuL1 and CuL2 complexes. The in vitro antibacterial assessment against E. coli and S. aureus revealed that the CuL1 and CuL2 complexes exhibited significantly better activity than Schiff bases HL1 and L2. Moreover, CuL2 exhibits greater bioactivity against both bacterial strains compared to CuL1. This difference could be attributed to a free hydroxy group, supported by computational analysis. Our findings suggest that the formation of complexes and the presence of free hydroxy groups may enhance the antibacterial activity of the drug.

Co, Cu, Ni, and Zn complexes of N-[(3-phenoxy phenyl)methylidene]-l-valine as α-glycosidase and α-amylase inhibitors: Synthesis, molecular docking & antimicrobial evaluation

The ligand N-[(3-phenoxyphenyl)methylidene]-l-valine (HL) and its Co, Ni, Cu, and Zn derivatives (1-4) were synthesized and characterized. These compounds were tested for α-glucosidase and α-amylase inhibition activity, showing IC50 values of 10.51-51.36 µg/mL and 15.38-46.74 µg/mL, respectively, compared to Ascarbose. In silico molecular docking studies revealed strong binding affinities for α-glucosidase (-207.78 to -222.04 kcal/mol) and α-amylase (-159.5 to -161.82 kcal/mol), and potential anticancer activity against CDK2 (-119.6 to -126.53 kcal/mol). Antimicrobial assays against E. coli and C. albicans demonstrated significant activity, with inhibition zones of 12.5-16.8 mm and 13.5-20.05 mm, respectively. The results reveal a fascinating array of pharmacological properties of these compounds and suggest their potential for future drug development.

Copper-mediated cyclization of thiosemicarbazones leading to 1,3,4-thiadiazoles: Structural elucidation, DFT calculations, in vitro biological evaluation and in silico evaluation studies

Cancer's global impact necessitates innovative and less toxic treatments. Thiosemicarbazones (TSCs), adaptable metal chelators, offer such potential. In this study, we have synthesized N (4)-substituted heterocyclic TSCs from syringaldehyde (TSL1, TSL2), and also report the unexpected copper-mediated cyclization of the TSCs to form thiadiazoles (TSL3, TSL4), expanding research avenues. This work includes extensive characterization and studies such as DNA/protein binding, molecular docking, and theoretical analyses to demonstrate the potential of the as-prepared TSCs and thiadiazoles against different cancer cells. The DFT results depict that the thiadiazoles exhibit greater structural stability and reduced reactivity compared to the corresponding TSCs. The docking results suggest superior EGFR inhibition for TSL3 with a binding constant value of - 6.99 Kcal/mol. According to molecular dynamics studies, the TSL3-EGFR complex exhibits a lower average RMSD (1.39 nm) as compared to the TSL1-EGFR complex (3.29 nm) suggesting that both the thiadiazole and thiosemicarbazone examined here can be good inhibitors of EGFR protein, also that TSL3 can inhibit EGFR better than TSL1. ADME analysis indicates drug-likeness and oral availability of the thiadiazole-based drugs. The DNA binding experiment through absorption and emission spectroscopy discovered that TSL3 is more active towards DNA which is quantitatively calculated with a Kb value of 4.74 × 106 M-1, Kq value of 4.04 × 104 M-1and Kapp value of 5 × 106 M-1. Furthermore, the BSA binding studies carried out with fluorescence spectroscopy showed that TSL3 shows better binding capacity (1.64 × 105 M-1) with BSA protein. All the compounds show significant cytotoxicity against A459-lung, MCF-7-breast, and HepG2-liver cancer cell lines; TSL3 exhibits the best cytotoxicity, albeit less effective than cisplatin. Thiadiazoles demonstrate greater cytotoxicity than the TSCs. Overall, the promise of TSCs and thiadiazoles in cancer research is highlighted by this study. Furthermore, it unveils unexpected copper-mediated cyclization of the TSCs to thiadiazoles.

Synthesis and Spectroscopic Characterization of Schiff Base Metal Complexes, Biological Activity, and Molecular Docking Studies

New cobalt(II), copper(II), and zinc(II) Schiff metal complexes were synthesized by the condensation reaction of 4-nitrobenzene-1,2-diamine with 3-4-(diethylamino)-2-hydroxybenzaldehyde. Fourier transform infrared, nuclear magnetic resonance, ultraviolet-visible, electron paramagnetic resonance, and high-resolution electrospray ionization mass spectrometry and powder X-ray diffraction were used to characterize the synthesized H2L and its metal complexes. Conductance measurements, magnetic moment estimation, and metal estimation have all been determined and discussed. The electrochemical properties of the synthesized compounds have been determined and discussed using cyclic voltammetry. The molecular structures of H2L and its metal complexes have been optimized using the B3LYP functional and the 6-31G (d,p) basis set, and their parameters have been discussed. The quantum chemical properties of these synthesized compounds have been predicted through charge distribution and molecular orbital analysis. The biological properties of the synthesized compounds' antioxidant, antifungal, and antibacterial activity have been studied and discussed. Furthermore, H2L and its complexes have been docked with HER2-associated target proteins in breast cancer.

An efficient new method of ytterbium(III) triflate catalysis approach to the synthesis of substituted pyrroles: DFT, ADMET, and molecular docking investigations

In this study, the one-pot synthetic methodology for the preparation of substituted pyrroles with diethyl acetylene-dicarboxylate is reported for the various pyrrole derivatives via the Trifimow synthesis process from oximes. This method also offers the literature as a cyclization pathway using a ytterbium triflate catalyst. Another importance of this study is the use of pyrrole derivatives in pharmaceuticals, biological processes, and agrochemicals. From this point of view, the development of a new catalyst in synthetic organic chemistry and the difference in the method is also important. The syntheses of the target substituted pyrroles are accomplished in high yields. Also, all synthesized structures were confirmed by 1H NMR, 13C NMR, and IR spectra. The DFT computations were leveraged for structural and spectroscopic validation of the compounds. Then, FMO and NBO analyses were subsequently employed to elucidate the reactivity characteristics and intramolecular interactions within these compounds. Also, ADMET indices were ascertained to assess potential pharmacokinetic properties, drug-like qualities, and possible adverse effects of these compounds. Last, optimized molecules were analyzed by molecular docking methods against crystal structures of Bovine Serum Albumin and Leukemia Inhibitory Factor, and their binding affinities, interaction details, and inhibition constants were determined.

Thioether-based novel transition metal complexes: Synthesis, DNA interaction, in vitro biological assay, DFT calculations, and molecular docking studies

A novel Schiff base ligand 2-(((2-(benzylthio)phenyl)imino)methyl)-4-chlorophenol and its cobalt, nickel, copper, and zinc metal complexes were prepared. Using B3LYP/6-31++G(d,p) method with LanL2DZ as basis set, the molecular structure of metal complexes has been optimized, and their parameters have been explored. The distorted octahedral geometries have been observed in cobalt, nickel, and copper complexes. In contrast, zinc complex exhibited distorted tetrahedral geometry indicating the coordination of metal ions with ligands through ONS binding sites, which are confirmed by various spectroscopic techniques, magnetic measurements, molar conductivity, elemental analysis, and DFT studies. The intercalative binding mode between CT-DNA and synthesized metal complexes has been determined by absorption and fluorescence spectroscopy. The binding constant values of metal complexes found to be varied from 5.28 × 10³ M^-1 to 9.18 × 10⁴ M^-1. Furthermore, several methods have been used to scrutinize the bioactivities, such as in vitro anti-diabetic, anti-inflammatory, and antioxidant. From the obtained results, it can be concluded that zinc metal complex exhibited excellent anti-inflammatory and anti-diabetic activity compared to others. However, the copper complex has good antioxidant property. Besides deducing the prospective binding energies of inhibitors, molecular docking simulations have also been conducted utilizing the enzyme structures of B-DNA, 6-COX, α-amylase, and α-glucosidase.

Synthesis and characterization of two new mixed-ligand Cu(II) complexes of a tridentate NN'O type Schiff base ligand and N-donor heterocyclic co-ligands: In vitro anticancer assay, DNA/human leukemia/COVID-19 molecular docking studies, and pharmacophore modeling

Two new mixed-ligand complexes with general formula [Cu(SB)(L')]ClO4 (1 and 2) were synthesized and characterized by different spectroscopic and analytical techniques including Fourier transform infrared (FT-IR) and UV-Vis spectroscopy and elemental analyses. The SB ligand is an unsymmetrical tridentate NN'O type Schiff base ligand that was derived from the condensation of 1,2-ethylenediamine and 5-bromo-2-hydroxy-3-nitrobenzaldehyde. The L' ligand is pyridine in (1) and 2,2'-dimethyl-4,4'-bithiazole (BTZ) in (2). Crystal structure of (2) was also obtained. The two complexes were used as anticancer agents against leukemia cancer cell line HL-60 and showed considerable anticancer activity. The anticancer activity of these complexes was comparable with the standard drug 5-fluorouracil (5-FU). Molecular docking and pharmacophore studies were also performed on DNA (PDB:1BNA) and leukemia inhibitor factor (LIF) (PDB:1EMR) to further investigate the anticancer and anti-COVID activity of these complexes. The molecular docking results against DNA revealed that (1) preferentially binds to the major groove of DNA receptor whereas (2) binds to the minor groove. Complex (2) performed better with 1EMR. The experimental and theoretical results showed good correlation. Molecular docking and pharmacophore studies were also applied to study the interactions between the synthesized complexes and SARS-CoV-2 virus receptor protein (PDB ID:6LU7). The results revealed that complex (2) had better interaction than (1), the free ligands (SB and BTZ), and the standard drug favipiravir.

Synthesis and crystal structures of new mixed-ligand Schiff base complexes containing N-donor heterocyclic co-ligands: molecular docking and pharmacophore modeling studies on the main proteases of SARS-CoV-2 virus (COVID-19 disease)

Three new mixed-ligand copper(II) complexes (1–3) with NN'O type unsymmetrical tridentate Schiff base ligands (SB) and N-donor heterocyclic co-ligands, with general formula [Cu(SB)(L)]ClO₄, were synthesized and characterized using single crystal x-ray diffraction (SCXRD), FT-IR and UV–Vis spectroscopy and elemental analyses. The SB ligand is the half-unit form of the condensation of 1,3-propanediamine with 5-methoxysalicylaldehyde and the co-ligands (L) are pyridine (py in (1)), 2,2′-bipyridine (bpy in (2)) and 1,10-phenanthroline (phen in (3)). Crystal structures of (2) and (3) were obtained by SCXRD. Molecular docking and pharmacophore studies were performed to study the interactions between the synthesized complexes and SARS-CoV-2 virus main proteases (PDB IDs: 6LU7, 6WQF and 6W9C). Results revealed that complex (3) with phen co-ligand showed better docking scores with the three receptors, i.e. 6LU7 (−8.05 kcal.mol⁻¹), 6W9C (−7.70 kcal.mol⁻¹) and 6WQF (−7.75 kcal.mol⁻¹). The order of the binding best energies for (3) was also as follows: 6LU7 > 6WQF > 6W9C. All of the studied complexes showed considerable performance, comparable to the standard drug, Favipiravir.