Synthesis, spectroscopic characterization, reactive properties by DFT calculations, molecular dynamics simulations and biological evaluation of Schiff bases tethered 1,2,4-triazole and pyrazole rings

Discovery of New Schiff Bases Tethered Pyrazole Moiety: Design, Synthesis, Biological Evaluation, and Molecular Docking Study as Dual Targeting DHFR/DNA Gyrase Inhibitors with Immunomodulatory Activity

A series of Bis-pyrazole Schiff bases (6a–d and 7a–d) and mono-pyrazole Schiff bases (8a–d and 9a–d) were designed and synthesized through the reaction of 5-aminopyrazoles 1a–d with aldehydes 2–5 using mild reaction condition with a good yield percentage. The chemical structure of newly formed Schiff bases tethered pyrazole core was confirmed based on spectral and experimental data. All the newly formed pyrazole Schiff bases were evaluated against eight pathogens (Gram-positive, Gram-negative, and fungi). The result exhibited that, most of them have good and broad activities. Among those, only six Schiff bases (6b, 7b, 7c, 8a, 8d, and 9b) displayed MIC values (0.97–62.5 µg/mL) compared to Tetracycline (15.62–62.5 µg/mL) and Amphotericin B (15.62–31.25 µg/mL), MBC values (1.94–87.5 µg/mL) and selectivity to tumor cell than normal cells. Immunomodulatory activities showed that the promising Schiff bases increase the immunomodulator effect of defense cell and the Schiff base 8a is the highest one by (Intra. killing activity = 136.5 ± 0.3%) having a pyrazole moiety as well as amide function (O=C-NH₂) and piperidinyl core. Furthermore, the most potent one exhibited broad activity depending on both MIC and MBC values. Moreover, to study the mechanism of these pyrazole Schiff bases, two active Schiff bases 8a and 9b from six derivatives were introduced to study the enzyme assay as dihydrofolate reductase (DHFR) on E. coli organism and DNA gyrase with two different organisms, S. aureus and B. subtilis, to determine the inhibitory activities with lower values in the case of DNA gyrase (8a and 9b) or nearly as DHFR compound 9b, while pyrazole 8a showed excellent inhibitory against all enzyme assay. The molecular docking study against dihydrofolate reductase and DNA gyrase were performed to study the binding between active site in the pocket with the two Schiff bases (8a and 9b) that exhibited good binding affinity with different bond types as H-bonding, aren-aren, and arene-cation interaction as well as study the physicochemical and pharmacokinetic properties of the two active Schiff bases 8a and 9b.

Co(ii) and Zn(ii) pyrazolyl-benzimidazole complexes with remarkable antibacterial activity

Three pseudopolymorphs based on a coordination complex of a pyrazolyl-benzimidazole ligand have been synthesized and characterized by single crystal X-diffraction, and showed remarkable antibacterial properties.

Crystal structure and Hirshfeld surface analysis of N-{2-[(E)-(4-methyl-benzyl-idene)amino]-phen-yl}-2-(5-methyl-1-H-pyrazol-3-yl)acetamide hemihydrate

The asymmetric unit of the title compound, C20H20N4O·0.5H2O, contains two independent organic mol-ecules (1 and 2) and a water mol-ecule of crystallization. The two mol-ecules differ primarily in the dihedral angles between the aromatic rings, which are 7.79 (7) and 29.89 (7)° in mol-ecules 1 and 2, respectively. In each mol-ecule there is intra-molecular C-H⋯O hydrogen bond forming an S(6) ring motif. In mol-ecule 1 there is an intra-molecular N-H⋯π(pyrazole) inter-action and an intra-molecular C-H⋯π(pyrazole) inter-action present. Mol-ecule 1 is linked to mol-ecule 2 by a C-H⋯π(benzene ring) inter-action. An intra-molecular N-H⋯N hydrogen bond and an intra-molecular C-H⋯N hydrogen bond are also present in mol-ecule 2. In the crystal, the three components are linked by Owater-H⋯N, N-H⋯Owater and N-H⋯N hydrogen bonds, forming chains along the [100] direction. The chains are linked by C-H⋯O and C-H⋯N hydrogen bonds, forming layers parallel to the ab plane. Finally, the layers are linked by C-H⋯π inter-actions, forming a three-dimensional structure.