Presence of π…π and C H…π interactions in the new Schiff base 2-{( E )-[(3- tert -butyl-1-phenyl-1 H -pyrazol-5-yl)imino]methyl}phenol: Experimental and DFT computational studies

Evaluation of the Antifungal Properties of Azomethine-Pyrazole Derivatives from a Structural Perspective

About 95 % of candidiasis infections worldwide are attributed to five Candida fungi species, with C. albicans being the most prevalent and severe. Due to resistance phenomena, the last decade has seen a significant challenge for candidiasis treatment with antifungal drugs, which has led to an urgent need for new antifungal agents. In this article, we report the synthesis of a series of azomethine-pyrazole derivatives bearing a para-substituted azo-phenyl ring. These compounds were evaluated as antifungal agents against Candida species and Cryptococcus neoformans strains. Compound ClAzoNH, substituted by chloride, displayed the highest toxicity on Candida albicans, with an MIC50 value of 2.08 μg/mL, while methoxy-substituted MeOAzoNH showed moderate inhibitory activity. The unsubstituted AzoNH compound exhibited the highest activity towards Candida tropicalis, Candida glabrata, Candida parapsilosis, and Candida krusei strains. In the case of C. albicans, the CaCYP51 protein appears to be the most probable biological target, while for C. neoformans, interactions with the CnFTase protein explained the in vitro results.

Co(II), Ni(II), and Zn(II) complexes based on new hybrid imine-pyrazole ligands: structural, spectroscopic, and electronic properties

The present work reports the theoretical investigation of Co(II), Ni(II), and Zn(II) complexes containing Schiff bases (used as ligands) derived from the reaction of 2-hydroxy-1-naphthaldehyde with N-(2-aminoethyl) pyrazoles. The spectral analyses were carried out using infrared, Raman, and UV-Vis spectroscopy. Vibrational analyses were performed in order to investigate the mechanisms involving metal-ligand and intra-ligand vibrations and indicated the possibility of charge transfer related to the transitions n[Formula: see text]* and [Formula: see text]*. Structure optimizations and normal coordinate force field calculations were performed via the density functional theory (DFT) method at the HSE06/6-311G(d,p)/LanL2DZ level. A thorough analysis was also conducted regarding the nonlinear optical (NLO) properties and the natural bond orbital (NBO) of the complexes. The results show that these complexes have prospective application as materials for NLO. Furthermore, the NBO analysis confirms the coordination between the lone pair (LP) electrons of the donor atoms (O and N) and the metal acceptors. Finally, studies were conducted regarding the electronic properties of the complexes; among the properties investigated included the frontier molecular orbitals (FMO) and the molecular electrostatic potential (MEP), allowing to determine the energy gap and charge distribution.

Crystalline Derivatives of Dipyrazolo-1,5-diazocine and Dipyrazolopyrimidine: A Case of Unexpected Synthesis and Isostructural Polymorphism

Pyrazole-phenylmethanimines (Shiff bases), Py–N=CH–Ph, form molecular crystals whose supramolecular and self-assembly properties can be tuned according to the substitution made on the aromatic and pyrazole rings. In pursuit of the first pyrazole-pyridinemethanimine member, Py–N=CH–Pyr, by following the well-known synthetic scheme for these Shiff bases, two hitherto unknown crystalline derivatives of dipyrazolo-1,5-diazocine and dipyrazolopyrimidine were obtained instead, this depending on the use or not of acetic acid as the catalyst. 1,5-diazocine crystallizes in a single P-1 triclinic packing system (Z = 2, Z′ = 1), while dipyrazolopyrimidine exhibits isostructural dimorphic behavior by adopting two (pale pink and yellow) alike P21/c monoclinic systems (both Z = 4, Z′ = 1) as a function of the solvent used. Crystal structures were resolved by means of X-ray diffraction technique and their intramolecular, intermolecular, and supramolecular assemblies analyzed with the assistance of decorated Hirshfeld surfaces and the topology study of electron density using the quantum-theory of atoms in molecules (QTAIM). Although both dipyrazolopyrimidine polymorphs are stabilized by the same type of noncovalent motifs, the pale pink crystal has a slightly more compact structure, with more efficient inter- and intramolecular interactions.

Synthesis, Structural Characterization, and In Vitro and In Silico Antifungal Evaluation of Azo-Azomethine Pyrazoles (PhN2(PhOH)CHN(C3N2(CH3)3)PhR, R = H or NO2)

The azo-azomethine imines, R¹-N=N-R²-CH=N-R³, are a class of active pharmacological ligands that have been prominent antifungal, antibacterial, and antitumor agents. In this study, four new azo-azomethines, R¹ = Ph, R² = phenol, and R³ = pyrazol-Ph-R’ (R = H or NO₂), have been synthesized, structurally characterized using X-ray, IR, NMR and UV–Vis techniques, and their antifungal activity evaluated against certified strains of Candida albicans and Cryptococcus neoformans. The antifungal tests revealed a high to moderate inhibitory activity towards both strains, which is regulated as a function of both the presence and the location of the nitro group in the aromatic ring of the series. These biological assays were further complemented with molecular docking studies against three different molecular targets from each fungus strain. Molecular dynamics simulations and binding free energy calculations were performed on the two best molecular docking results for each fungus strain. Better affinity for active sites for nitro compounds at the “meta” and “para” positions was found, making them promising building blocks for the development of new Schiff bases with high antifungal activity.