Synthesis, characterization, equilibrium studies, and biological activity of complexes involving copper(II), 2-aminomethylthiophenyl-4-bromosalicylaldehyde Schiff base, and selected amino acids

Protonation constants of endo- and exogenous L-amino acids and their derivatives in aqueous and mixed solution: Unraveling molecular secrets

The aim of this review is to summarize the progress made in the determination of the protonation constants of biologically active ligands: endo- and exogenous L-amino acids and their derivatives in aqueous and mixed solutions using different experimental techniques. The knowledge of the protonation constants of the aforementioned ligands is crucial for the determination of the equilibrium constants of complex formation and thus for the understanding of complex biological reactions such as transamination, racemization, and decarboxylation. Thus, the protonation constants of ligands are a measure of their ability to form complexes with metal ions. This knowledge not only helps to understand fundamental biochemical processes, but also has practical applications in areas such as drug design, where ligands are often targeted for therapeutic purposes. The activity of the ligands tends to increase after complexation and their order is consistent with the values of the stepwise dissociation constants of the complexes formed. Understanding the properties of ligands by determining their protonation constants in different environments and their interactions with surrounding molecules is crucial to unraveling the complexity of biological systems.

Synthesis and Biological Evaluation of Novel Zn(II) and Cd(II) Schiff Base Complexes as Antimicrobial, Antifungal, and Antioxidant Agents

(E)-N,N-Dimethyl-2-((E-1-(2-(p-tolyl)hydrazono)propan-2-ylidene)hydrazine-1-carbothioamide (DMPTHP) and their Zn(II) and Cd(II) complexes have been synthesized and characterized. Different tools of analysis such as elemental analyses, IR, mass spectra, and 1H-NMR measurements were used to elucidate the structure of the synthesized compounds. According to these spectral results, the DMPTHP ligand behaved as a mononegatively charged tridentate anion. Modeling and docking studies were investigated and discussed. Novel Schiff base (DMPTHP) ligand protonation constants and their formation constants with Cd(II) and Zn(II) ions were measured in 50% DMSO solution at 15°C, 25°C, and 35°C at I = 0.1 mol·dm−3 NaNO3. The solution speciation of different species was measured in accordance with pH. Calculation and discussion of the thermodynamic parameters were achieved. Both log K1 and –ΔH1, for M(II)-thiosemicarbazone complexes were found to be somewhat larger than log K2 and –ΔH2, demonstrating a shift in the dentate character of DMPTHP from tridentate in 1 : 1 chelates to bidentate in 1 : 2; M : L chelates and steric hindrance were generated by addition of the 2nd molecule. The compounds prepared have significant activity as antioxidants, similar to ascorbic acid. It is hoped that the results will be beneficial to antimicrobial agent chemistry. The formed compounds acted as a potent antibacterial agent. Molecular docking studies were investigated and have proved that DMPTHP as antibacterial agents act on highly resistant strains of E. coli and also as an anticancer agent.

Oxygen activation by copper camphor complexes

In situreduction of CuCl₂enables formation of Cu(i) complexes prone to activate molecular oxygen from air towards catalytic oxidation of 1,3-dicarbonyls.

Protonation equilibria of biologically active ligands in mixed aqueous organic solvents

The review is mainly concerned with the protonation equilibria of biologically active ligands like amino acids, peptides, DNA constituents, and amino acid esters in nonaqueous media. Equilibrium concentrations of proton-ligand formation as a function of pH were investigated. Also, thermodynamics associated with protonation equilibria were also discussed.