Design and synthesis of Schiff base Homobimetallic-Complexes as promising antimicrobial agents

Substituent effect on the chemical and biological properties of diisatin dihydrazone Schiff bases: DFT and docking studies

According to the considered role of lipophilicity-hydrophobicity on organic Schiff base hydrazones, different substituents of phenyl, ethyl, and methyl groups were inserted in the synthetic strategy of diisatin dihydrazones (L1-4). The biochemical enhancement was evaluated depending on their inhibitive potential of the growth power of three human tumor cells, fungi, and bacteria. The biochemical assays assigned the effected role of different substituents of phenyl, ethyl, and methyl groups on the effectiveness of their diisatin dihydrazone reagents. The interacting modes with calf thymus DNA (i.e. Ct-DNA) were studied via viscometric and spectrophotometric titration. The organo-reagent L1 with the oxalic derivative assigned a performed inhibitive action for the examined microbes and the human tumor cell lines growing up over the terephthalic (L4) > malonic (L2) > succinic (L3) ones. From Kb = binding constant, and ∆Gb≠ = Gibb's free energy values, the binding of interaction within Ct-DNA was evaluated for all compounds (L1-4), in which L1, L3, and L4 assigned the highest reactivity referring to the covalent/non-covalent modes of interaction, as given for (L1-4), 14.32, 13.28, 10.87, and 12.41 × 107 mol-1 dm3, and -45.17, -43.24, -43.75, and -44.05 kJ mol-1, respectively. DFT and docking studies were achieved to support the current work.

Bidentate bromhexine drug coordination modes with various transition metal ions: Synthesis, characterization, and in vitro antibacterial and anti-breast cancer activity tests

BACKGROUND

Bromhexine (BHX) is a mucolytic drug used in treatment the respiratory disorders which are associated with excessive or viscid mucus. Transition metal complexes have made tremendous progress in the treatment of a variety of human ailments, according to reported articles. Transition metal complexes are being developed as medications with a lot of effort. Metal complexes can form a variety of coordination geometries, giving them distinct forms. So, binary metal complexes of bromhexine drug have been prepared to enhance the biological activity and stability of the free drug.

METHODS

A new series of binary complexes with bromhexine drug (BHX) has been prepared with some transition metal ions namely Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II). Elemental analyses, FT-IR, mass spectrometry, thermal studies and UV-Vis spectra have been used to characterize and structurally elucidate the produced metal complexes. Antibacterial activity has been tested for the ligand and metal complexes against a variety of pathogenic bacterial species (Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus). In addition, the ligand has been tested for anticancer efficacy against the MCF-7 breast cancer cell line, as opposed to binary metal complexes. The binding orientation or conformation of the free BHX ligand and Co(II) complex in the active region of the protein of crystal structure of Escherichia coli (PDB ID: 3T88) and Pseudomonas aeruginosa (PDB ID: 6NE0) has been performed using molecular docking studies.

RESULTS

The BHX ligand coupled in neutral bidentate mode to the metal ions, according to FT-IR and 1H-NMR spectral results. The molar conductivity measurements of the complexes in DMF proved the electrolytic nature of all binary complexes. Co(II) complex showed the highest inhibition zone diameter against S. aureus, E. coli and P. aeruginosa. Zn(II) complex had the greatest inhibitory effect against P. aeruginosa and B. subtilis. Also, Cd(II) chelate appeared high efficacy as antibacterial agent against Pseudomonas aeruginosa and Staphylococcus aureus.

CONCLUSION

All the output data conjugated to confirm the octahedral geometry of the metal complexes. The biological findings revealed that metal complexes can be more active than the free BHX ligand. Against MCF-7 cell line, Cd(II)-L complex is highly active complex (4.95 µg/mL) but BHX free drug is the most active compound (3.96 µg/mL).

Cerium(IV) Pyrasal Complexes: A pH-Dependent 8- to 10-Coordinate Cerium Chelate Switch

In this work, five cerium(IV) complexes were synthesized, three of which were structural isomorphs from the same pyrasal ligand with the solid-state result identified by structural analysis dependent on the initial pH of the reaction solution and the temperature at which the reaction is performed. The ligands explored here are pyrasal ligands, which are Schiff-base ligands formed by the condensation of 2,3-diaminopyrazine and a salicylaldehyde derivative. Pyrasal ligands have weaker binding than other salophen-type ligands due to the electron-withdrawing effect of the nitrogen atoms contained within the pyrazine ring. The weaker binding leaves the ligand more susceptible to the changes in pH and temperature that alternate the chelating environment from 8- to 10-coordinate. This electron-withdrawing effect of the pyrazine backbone also deactivates the second amine after the first condensation addition of salicylaldehyde. Without a metal to template the complex formation reaction, even with extended reaction times and the addition of a large excess of ligand, the result is the addition of only one salicylaldehyde.

Ease to Challenges in Achieving Successful Synthesized Schiff Base, Chirality, and Application as Antibacterial Agent

This study reports how to overcome the challenges experienced in achieving successful synthesized Schiff base via types of Schiff base (chiral and achiral), synthesis, nature of products, and its antibacterial applications. Schiff base is a versatile ligand which is useful in asymmetric reactions to prepare chiral catalysts. It is also used in symmetric reactions to prepare achiral compounds. In line with the achiral compounds, conventional (room temperature and refluxing) and microwave irradiation methods are the two main types of methods to synthesize achiral Schiff base as reported in this review. Among various experimental approaches, this study supports the green chemistry microwave approach to synthesize Schiff base because of its benefits environmental sustainability. Problems relating to the nature of products formed from the synthesized Schiff bases were examined and resolved. Herein, the products could either be solid (crystals, powder, and precipitate), oily, or viscous (sticky) products. Some familiar characterization techniques used to identify and confirm the successful syntheses of Schiff bases, such as solubility test, melting point (MP), Fourier transform infrared (FTIR), ultraviolet-visible (UV-Vis), and nuclear magnetic resonance (NMR, 1H NMR, and 13C NMR), were discussed. In addition, the antibacterial studies on Schiff base and corresponding metal complexes confirmed their biological relevance to the human.

{2-(((2-aminoethyl)imino)methyl)-6-bromophenolato-κ3 N,N′,O}iron(III) nitrate, C18H20Br2FeN5O5

C18H20Br2FeN5O5, monoclinic, P21/c (no. 14), a = 12.4534(3) Å, b = 10.8106(3) Å, c = 16.0339(4) Å, β = 94.0450(10)°, V = 2153.25(10) Å3, Z = 4, R gt(F) = 0276, wR ref(F 2) = 0.0644, T = 170.0 K.