Detailed Structural Examination, Quantum Mechanical Studies of the Aromatic Compound Solarimfetol and Formation of Inclusion Compound with Cucurbituril

Complexes between 2,2'-azobis(2-methylpropionamidine) dihydrochloride (AAPH) and cucurbit[n]uril hosts modulate the yield and fate of photolytically-generated AAPH radicals

Using theoretical and experimental tools we investigated the recognition of AAPH (2,2'-azobis(2-methylpropionamidine) dihydrochloride), a well-known water-soluble azo-compound employed as a source of peroxyl radicals, by cucurbit[6]uril (CB[6]), and cucurbit[8]uril (CB[8]). Density functional theory calculations and isothermal titration calorimetry experiments demonstrated that AAPH was not included in the cavity of CB[6], however, an exclusion complex was generated. Inclusion of AAPH in the CB[8] cavity was favored, forming stable inclusion complexes at 1 : 1 and 2 : 1 stoichiometries; AAPH@CB[8] and 2AAPH@CB[8], respectively. Radical formation upon photolytic cleavage of AAPH was examined theoretically, and by spin trapping with electron paramagnetic resonance. The radical yields detected with uncomplexed (free) AAPH and the AAPH-CB[6] (exclusion) complex were identical, whereas a marked decrease was shown for AAPH@CB[8]. Lower decreases were seen with a bimolecular (2 : 1) AAPH-CB[8] inclusion complex (2AAPH@CB[8]). This modulation was corroborated by the consumption of pyrogallol red (PGR), an oxidizable dye that does not associate with CB[6] or CB[8]. AAPH-CB[6] and 2AAPH@CB[8] did not significantly modify the initial consumption rate (Ri) of PGR, whereas AAPH@CB[8] decreased this. The oxidative consumption of free Trp, Gly-Trp and Trp-Gly by radicals derived from AAPH in the presence of CB[8] showed a dependence on the association of the targets with CB[8].

Unveiling the Intermolecular Interactions between Drug 5-Fluorouracil and Watson-Crick/Hoogsteen Base Pairs: A Computational Analysis

The adsorption of 5-fluorouracil (5FU) on Watson-Crick (WC) base pairs and Hoogsteen (HT) base pairs has been studied using the dispersion-corrected density functional theory (DFT). The adsorption, binding energy, and thermochemistry for the drug 5FU on the WC and HT base pairs were determined. The most stable geometries were near planar geometry, and 5FU has a higher preference for WC than HT base pairs. The adsorption energies of 5FU on nucleobase pairs are consistently higher than pristine nucleobase pairs, indicating that nucleobase pair cleavage is less likely during the adsorption of the 5FU drug. The enthalpy change for the formation of 5FU-DNA base pairs is higher than that for the formation of 5FU-nucleobases and is enthalpy-driven. The E gap of AT base pairs is higher, suggesting that their chemical reactivity toward further reaction would be less than that of GC base pairs. The electron density difference (EDD) analysis shows a significant decrease in electron density in aromatic regions on the purine bases (adenine/guanine) compared to the pyrimidine bases. The MESP diagram of the stable 5FU-nucleobase pair complexes shows a directional interaction, with the positive regions in a molecule interacting with the negative region of other molecules. The atoms in molecule analysis show that the ρ(r) values of C=O···H-N are higher than those of N···H/N-H···O. The N···H intermolecular bonds between the base pair/drug and nucleobases are weak, closed shell interactions and are electrostatic in nature. The noncovalent interaction analysis shows that several new spikes are engendered along with an increase in their strength, which indicates that the H-bonding interactions are stronger and play a dominant role in stabilizing the complexes. Energy decomposition analysis shows that the drug-nucleobase pair complex has a marginal increase in the electrostatic contributions compared to nucleobase pair complexes.

Schiff Bases from α-ionone with Adenine, Cytosine, and l-leucine Biomolecules: Synthesis, Structural Features, Electronic Structure, and Medicinal Activities

Tea is a very important source of the terepenoid [Formula: see text]-ionone, which is much appreciated as a medicinal beverage. Schiff bases are a very important class of organic compounds usually formed by the condensation of carbonyl compounds with amines. [Formula: see text]-ionone is a carbonyl terpenoid obtained from Schiff bases on condensation with nucleobases like adenine and cytosine and the amino acid [Formula: see text]-leucine. We synthesized these three Schiff bases and characterized them using UV, FTIR, and H1 and C13-NMR spectra. The molecules were optimized using B3LYP/6-311+G(2d,p) level followed by the simulation of FT-IR spectra, of which the simulated and experimental spectra showed complete agreement. The UV spectra were simulated using TD-DFT, and the electronic excitations were carefully analyzed. Natural bond orbitals provided an analysis of the stability of the compound, which is supplemented by the data from frontier molecular orbital analysis. Detailed wavefunction analysis is reported which predicts the active centers, reactivity profile, and the extent of non-covalent interactions. PASS indicated that compounds show antieczemic properties and antiarthritic properties, which is confirmed with the help of molecular docking results.