A DFT study on the structure activity relationship of the natural xanthotoxin-based pharmaceutical cocrystals

In this work, the pharmaceutical cocrystals xanthotoxin-para-aminobenzoic acid (XT-PABA) and xanthotoxin-oxalic acid (XT-OA) were systematically investigated in the gas and water phases by using the quantum chemical approach. The weak intermolecular interactions have been estimated and the O1…H4 (O1…H5) intermolecular hydrogen bond (IHB) with moderate intensity and partial covalent natures was confirmed based on the computed structural parameters, topology analysis, and reduced density gradient (RDG) isosurfaces. The electrophilic and nucleophilic reactivities of different positions associated with intermolecular interactions in XT, PABA, and OA were predicted by plotting the molecular electrostatic potential (MESP) diagrams. The calculated natural bond orbital (NBO) population analysis has quantitatively unveiled the intrinsic reason for the variations in weak intermolecular interactions within XT-PABA and XT-OA cocrystals, from the gas phase to the water phase. Besides, the frontier molecular orbitals (FMOs), Fukui function, and various global reactivity descriptors were computed to measure the chemical reactivity of all the investigated molecular systems. The XT-PABA and XT-OA cocrystals explored in this work could be regarded as valuable exemplar systems to design and synthesize the high-efficiency pharmaceutical cocrystals in the experiment.

Experimental and theoretical study for removal of trimethoprim from wastewater using organically modified silica with pyrazole-3-carbaldehyde bridged to copper ions

BACKGROUND

Human and veterinary antibiotics are typically discharged as parent chemicals in urine or feces and are known to be released into the environment via wastewater treatment plants (WWTPs). Several research investigations have recently been conducted on the removal and bioremediation of pharmaceutical and personal care products (PPCPs) disposed of in wastewater.

RESULTS

SiNP-Cu, a chelating matrix, was produced by delaying and slowing 1.5-dimethyl-1H-pyrazole-3-carbaldehyde on silica gel from functionalized with 3-aminopropyltrimethoxysilane. The prepared sorbent material was characterized using several techniques including BET surface area, FT-IR spectroscopy, Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and nitrogen adsorption-desorption isotherm. The pseudo-second-order model provided the best correlation due to the big match between the experimental and theoretical of different adsorption coefficients. The Langmuir and Freundlich adsorption models were used and the study showed a better match with the Freundlich model with a capacity of removal reached up to 420 mg g^-1. The removal capacity was dependent on pH and increased by increasing pH. The removal percentage reached 91;5% at pH = 8. The adsorbent demonstrated a high percentage removal of TMP, reaching more than 94% when increased pH. The sample was simply regenerated by soaking it for a few minutes in 1 N HCl and drying it. The sorbent was repeated five times with no discernible decrease in removal capacity. The thermodynamic study also showed endothermic, increasing randomness and not spontaneous. The free energy was 2.71 kJ/mol at 320 K. The findings of the DFT B3LYP/6-31 + g (d, p) local reactivity descriptors revealed that nitrogen atoms and π-electrons of the benzene and pyrimidine rings in the TMP are responsible for the adsorption process with the SiNP surface. The negative values of the adsorption energies obtained by molecular dynamic simulation indicated the spontaneity of the adsorption process.

CONCLUSION

The global reactivity indices prove that TMP is stable and it can be removed from wastewater using SiNP surface. The results of the local reactivity indices concluded that the active centers for the adsorption process are the nitrogen atoms and the π-electrons of the pyrimidine and benzene rings. Furthermore, the positive value of the maximum charge transfer number (ΔN) proves that TMP has a great tendency to donate electrons to SiNP surface during the process of adsorption.

Conceptual DFT and TDDFT study on electronic structure and reactivity of pure and sulfur doped (CrO3)n (n = 1-10) clusters

Different isomers of (CrO₃)_n (n = 1-10) cluster units have been investigated using Density functional approach. Their stability and reactivity has been analyzed by plotting chemical potential and HOMO-LUMO gap as a function of cluster size. The CrO₃, (CrO₃)₆ and (CrO₃)₉ are identified as the most reactive species. Reactivity of each atomic site in the cluster has been interpreted using local reactivity descriptors called Fukui Function plots. The clusters have been doped with sulfur by adding it as substitutional impurity, effect of sulfur doping has been understood by analyzing excitation energies and absorption wavelengths using time dependent-DFT(TDDFT) at CAM-B3LYP level of theory.

Understanding structure-activity relation in VxOy clusters of varied stoichiometry and sizes through conceptual density functional approach

Computations have been performed on V_xO_y clusters (with x = 1-8, y = 1-21) to explore their structure, stability, and reactivity based on local and global reactivity descriptors defined within the formalism of density functional theory (DFT). The vertical and adiabatic ionization energies and electron affinities are in accordance with Franck-Condon principle and suggest that the V_xO_y clusters are more likely to be electron acceptors than donors. The structure and reactivity of V_xO_y clusters delicately depend on their oxygen content and environment. Distinct active sites have been identified for each cluster species on the basis of coordination, symmetry, and charge distribution. The propensity of all the reactive sites towards an approaching electrophile and/or nucleophile has been studied using local reactivity descriptor. In oxygen-poor clusters, the vanadium atoms are more prone to nucleophilic attack. With an increase in oxygen concentration, the coordination number of vanadium increases and reaches four-fold, the site for nucleophilic attack shifts to terminal oxygens. We conclude that of all the stoichiometries, the stable V_xO_y clusters have the (VO₃)_a(V₂O₅)_b formula unit_. The localization of positive charge density in cubic cage structure of V₈O₂₀ successfully traps halide ions (F^-, Cl^-, and Br^-). In view of increasing use of metal oxide clusters in heterogeneous catalysis, the understanding of structure-activity relationship in vanadium oxides' clusters provided in the current study is highly desirable.

Synthesis, spectral characterization and computed optical analysis of potent triazole based compounds

Biologically active triazole Schiff base ligand (L) and metal complexes [Fe(II), Co(II), Ni(II), Cu(II) and Zn(II)] are reported herein. The ligand acted as tridentate and coordinated towards metallic ions via azomethine-N, triazolic-N moiety and deprotonated-O of phenyl substituents in an octahedral manner. These compounds were characterized by physical, spectral and analytical analysis. The synthesized ligand and metal complexes were screened for antibacterial pathogens against Chromohalobacter salexigens, Chromohalobacter israelensi, Halomonas halofila and Halomonas salina, antifungal bioassay against Aspergillus niger and Aspergellus flavin, antioxidant (DPPH, phosphomolybdate) and also for enzyme inhibition [butyrylcholinesterase (BChE) and acetylcholinesterase (AChE)] studies. The results of these activities indicated the ligand to possess potential activity which significantly increased upon chelation. Moreover, vibrational bands, frontier molecular orbitals (FMOs) and natural bond analysis (NBO) of ligand (1) were carried out through density functional theory (DFT) with B3lYP/6-311++G (d,p) approach. While, UV-Vis analysis was performed by time dependent TD-DFT with B3lYP/6-311++G (d,p) method. NBO analysis revealed that investigated compound (L) contains enormous molecular stability owing to hyper conjugative interactions. Theoretical spectroscopic findings showed good agreement to experimental spectroscopic data. Global reactivity descriptors were calculated using the energies of FMOs which indicated compound (L) might be bioactive. These parameters confirmed the charge transfer phenomenon and reasonable correspondence with experimental bioactivity results.