Novel Schiff base ligand based on the condensation of 4,6‐diacetyl resorcinol with 2‐amino‐4‐methylthiazole in addition to its metal complexes with Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) ions have been synthesized. The structure, electronic properties, and thermal behaviour of Schiff base and its metal complexes have been studied by elemental analysis, mass, 1H NMR, IR spectra, thermal analysis, and theoretically by density function theory. The ligand acted as mononegative bidentate (NO) ligand and all complexes showed octahedral geometry except Cu (II) showed tetrahedral geometry as indicated from the spectral and magnetic studies. The Cu (II), Zn (II) and Cd (II) complexes were non electrolytes while the rest of the complexes were electrolytes. The antibacterial plus anticancer activities of the parent Schiff base and its metal complexes were screened. In addition, the molecular docking study was performed to explore the possible ways for binding to Crystal Structure of Human Astrovirus capsid protein (5ibv) receptor.

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Novel Schiff base ligand was prepared by the condensation of 2,2-(ethylenedioxy)bis(ethylamine) and imidazole-2-carboxaldehyde in a 1:2 ratio, and its complexes with Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), and Cd(II) metal ions were synthesized in a 1:1 ratio. Various methods were used to identify the Schiff base ligand and complexes. Characterization techniques such as infrared, UV, and 1 H NMR spectral tests, elemental analysis, molar conductivity, magnetic properties, thermal analysis, BET surface area, and theoretically by DFT were used to help further understanding of the complex structures. For all complexes, the ligand behaved as a neutral tetradentate ligand with NOON donor atoms and spectroscopic studies indicated an octahedral structure. The electrolytic behavior of the complexes was revealed by the molar conductivity measurements. In addition, thermogravimetric analysis was used to investigate the decomposition of the complexes and Schiff base ligand. According to the results obtained, the antibacterial activity of the metal complexes is higher than that of the Schiff base ligand against one or more bacterial species. The results showed that Cd(II) complex exhibits enhanced activity against Aspergillus flavus and Ni(II) complex against Candida albicans than the standard drug ketoconazole. The Mn(II) complex had stronger activity against human breast cancer cell line (MCF-7) than the other complexes. Antiviral drug development is critical in the latest outbreak of a novel coronavirus (SARS-CoV-2). The new coronavirus was screened using molecular docking. Supplementary Information The online version contains supplementary material available at 10.1007/s13738-021-02359-w.

Mononuclear chelates of Cr(III), Mn(II), Fe(III), Ni(II), Cu(II), Zn(II) and Cd(II) resulting from new tridentate Schiff base ligand , 4-((1-(5-acetyl-2,4-dihydroxyphenyl)ethylidene)amino)-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one, were synthesized and characterized via various spectroscopic methods. Metal to ligand ratio was found to be 1:1, which was revealed via elemental analysis. IR has sharp out that the coordination of the ligand towards the metal ions was carried out via NOO atoms. UV-Vis, 1 HNMR spectral data, molar conductance measurements, BET surface area, melting points and theoretically through density function theory were used such as characterizing techniques in supporting of further interpretation of the complexes structures. The complexes were octahedral except Cu(II) and Ni(II) complexes were tetrahedral as suggested through the magnetic moment measurement. The complexes were found to have surface area, pore volume and particle radius 23-176 m 2 g -1 , 0.02-0.33 cc/g and 8.71-4.32 nm, respectively, as pointed out from BET measurement. Schiff base ligand and its metal complexes were tested in vitro to estimate their bactericidal activity opposed to Gram-negative and Gram-positive bacteria and antifungal organisms. In the recent incident of a novel coronavirus (SARS-CoV-2) spreads, antiviral drug detection is of most importance. MOE 2008 was used headed for screen potential drugs with molecular docking by the structural protein and non-structural protein sites of new coronavirus and the study was constructed to molecular docking without validation through MD simulations. Interactions with the main protease may play a key role in fighting against viruses.

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The condensation reaction between 5‐amino‐1,3,4‐thiadiazole‐2‐thiol and 1,2‐dibromoethane to afford the ligand L was carried out in direct to obtain the desired organic ligand. New [Er(L)ClH2O]Cl2·3H2O, [Yb(L)(H2O)2]Cl3·4H2O, and [Ta(L)Cl2]Cl3·4H2O complexes have been prepared from (L) by reacting one mole from metal ions with one mole from L. In addition to their physical characteristics, they were described using spectroscopic techniques (infrared [IR], nuclear magnetic resonance [NMR], and UV–Vis), gas chromatography (GC)‐mass, and X‐ray powder diffraction. Further interpretation of complex structures was supported by measurements of molar conductivity, magnetic susceptibility, mole ratio, and thermodynamic investigations in addition to theoretical study through the use of density functional theory and characterization techniques. IR spectral data showed the mode of action of the neutral tetradentate L ligand and its coordination via two N‐amine and two S‐thiols. The octahedral geometry surrounding the central lanthanide ions was suggested by the magnetic moments, diffused reflectance, and spectral data. Molar conductivity results exposed that Yb(III) and Ta(V) chelates were 1:3 electrolytes and Er(III) chelate was 1:2 electrolyte. In addition, practically all the complexes demonstrated effective antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, and Staphylococcus aureus species, via inhibition zone diameters in 9–15 mm mg−1 range. However, neither Candida albicans nor Aspergillus flavus species were susceptible to their antifungal effects. Finally, molecular docking (MOE) experiments showed the significant binding affinity of the ligand and its complexes with several 6KOC, 6LU4, and 6LU4 protein receptors. Finally, it is important to emphasize that these complexes may be potential antioxidant agents according to the biochemical results. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PP) methods were accustomed to examine the corrosion inhibition of aluminum silicon alloys (AlSi) in 1 M HCl solution. Experimental measurements indicate that the thiadiazole ligand reduces the corrosion rate.

A new tetradentate Schiff base ligand was prepared from condensation of 4,6-dihydroxy-1,3-phenylenediethanone with ethane-1,2-diylbis(oxy)diethanamine. The ligand forms complexes in good yield. The Schiff base and its complexes were characterized by analytical (CHN elemental analyses, solubility, melting point, conductivity) measurements, spectral (IR, UV-vis, 1H NMR and MS) and magnetic measurements. The elemental analyses, Uv-vis spectra, and room temperature magnetic moment data and theoretically through density function theory were used as characterizing techniques in supporting of further interpretation of the complexes structures. The results of elemental analyses, EI-mass and conductivity measurements confirmed the stoichiometry of the ligand and its complexes while the characteristic absorption bands and resonance peaks in IR and NMR spectra confirmed the formation of the ligand frameworks around the metal ions. The octahedral environment for complexes derived from Schiff base ligand have been confirmed on the basis of results of electronic and diffused reflectance spectral studies and magnetic moment measurements. Detailed studies of the thermal properties of the Schiff base ligand and complexes were investigated by thermogravimetric technique. Moreover, the molecular docking into (PDB: 6NE0) was the DNA binding and supports the experimental finding and 6IY0 Crystal structure of conserved hypothetical protein SAV0927 from Staphylococcus aureus subsp. aureus Mu50. The synthesized ligand and its complexes were tested for in vitro antimicrobial activity against Candida albicans, Bacillus subtilis, Aspergillus flavus, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus by using agar-well diffusion method.