Spectroscopic and nonlinear optical investigations of biscinnamyl-sulfone derivatives: Computational and experimental insights.

Novel geometrically asymmetric biscinnamyl-sulfone compounds (6a-c) with donor-π-conjugated spacer-acceptor functionality were successfully synthesized. This was achieved by coupling cinnamaldehyde precursors with 3,3'-diaminodiphenyl sulfone in dry organic solvents, resulting in high yields. Several spectroscopic techniques were employed to identify the derivatives. The absorption spectra of these compounds exhibited broad bands that spanned up to 120 nm, which can be attributed to their extended conjugation systems. In order to explore the electronic transitions of these materials, Time-Dependent Density-Functional Theory (TD-DFT) with EIFPCM solvation mode was utilized. We computationally investigated the static nonlinear optical (NLO) parameters, including dipole moments (µ), polarizability (α), anisotropic polarizability (Δα), first-order hyperpolarization (ß), and second-order hyperpolarization (γ). Although the new structures possess different functional groups, they displayed similar electronic potentials when their molecular electrostatic potentials were plotted. These potentials are crucial in stabilizing the molecules in crystal systems through noncovalent forces such as C-H⋯π stacking and hydrogen bonding. They also provide insights into the electronic assessments and energetics of these individual forces. By estimating the frontier orbitals, we gained an understanding of the intramolecular charge transfer in the compounds. Energy gap values were determined using the orbitals of density of states method and experimentally via the Tauc method. The computational and experimental results were in good agreement. Lastly, we examined the influence of different protic and aprotic solvents on the absorption bands of compound 6b, as an example. This compound showed a significant bathochromic shift of 41 nm upon changing the solvent from acetic acid to dimethyl sulfoxide.

Solvent Influence on Absorption Spectra and Tautomeric Equilibria of Symmetric Azomethine-Functionalized Derivatives: Structural Elucidation and Computational Studies.

A new series of azomethine-functionalized compounds was synthesized from the condensation of 2-hydroxy-1,3-propanediamine and 2-thienylcarboxaldehydes in the presence of a drying agent. The derivatives were spectroscopically characterized by NMR, LC-MS, UV/Vis, IR and elemental analysis. Variable temperature 1 H-NMR (-60 to +60 °C) was performed to investigate the effect of solvent polarity; the capability of solvent to form H-bond was found to dramatically influencing the tautomerization process of the desired structures. The calculated thermochemical parameters (ΔH298 , ΔG298 and ΔS298 ) at DFT and MP2 levels of theory explained that 3 b exists in equilibrium with two tautomers. The basis of the electronic absorptions was pursued through Time-Dependent Density-Functional Theory (TD-DFT). Analysis of the structural surfaces was inspected and the molecular electrostatic potential (MEP) demonstrated that the three functionalized compounds were relatively analogous in the electronic distributions. Furthermore, the electrophilic and nucleophilic centers lying on the molecular surfaces were probably playing a key-role in stabilizing the compounds through the nonclassical C-H⋅⋅⋅π interactions and hydrogen bonding. The impact of solvent polarity on absorption spectra were investigated via solvatochromic shifts. For instance, compound 3 c displayed a gradual shift of the maximum absorption to the red area when the solvent polarity was increased, recording a 21 nm of bathochromic shift. In contrast, no significant solvent-effect on 3 a and 3 b was observed. The solvation relation was pursued between Gutmann's donicity numbers the experimental λmax ; exhibited almost positive linear performance with a minor oscillation, that ascribe to the possible weak interface between the molecules of solute and designated solvents. The bandgap energy of all products were assessed experimentally using optical absorption spectra following Tauc approach, giving -4.050 (3 a), -3.900 (3 b) and -3.210 (3 c) eV. However, the ΔE were computationally figured out from TD-DFT simulation to be -4.258 (3 a), -4.022 (3 b) and -3.390 (3 c) eV.

Further Biochemical Profiling of Hypholoma fasciculare Metabolome Reveals Its Chemogenetic Diversity.

Natural products with novel chemistry are urgently needed to battle the continued increase in microbial drug resistance. Mushroom-forming fungi are underutilized as a source of novel antibiotics in the literature due to their challenging culture preparation and genetic intractability. However, modern fungal molecular and synthetic biology tools have renewed interest in exploring mushroom fungi for novel therapeutic agents. The aims of this study were to investigate the secondary metabolites of nine basidiomycetes, screen their biological and chemical properties, and then investigate the genetic pathways associated with their production. Of the nine fungi selected, Hypholoma fasciculare was revealed to be a highly active antagonistic species, with antimicrobial activity against three different microorganisms: Bacillus subtilis, Escherichia coli, and Saccharomyces cerevisiae. Genomic comparisons and chromatographic studies were employed to characterize more than 15 biosynthetic gene clusters and resulted in the identification of 3,5-dichloromethoxy benzoic acid as a potential antibacterial compound. The biosynthetic gene cluster for this product is also predicted. This study reinforces the potential of mushroom-forming fungi as an underexplored reservoir of bioactive natural products. Access to genomic data, and chemical-based frameworks, will assist the development and application of novel molecules with applications in both the pharmaceutical and agrochemical industries.

Mechanistic investigation of the Ru-catalyzed hydroamidation of terminal alkynes.

The ruthenium-catalyzed hydroamidation of terminal alkynes has evolved to become a broadly applicable tool for the synthesis of enamides and enimides. Depending on the catalyst system employed, the reaction leads chemo-, regio-, and stereoselectively to a single diastereoisomer. Herein, we present a comprehensive mechanistic study of the ruthenium-catalyzed hydroamidation of terminal alkynes, which includes deuterium-labeling, in situ IR, in situ NMR, and in situ ESI-MS experiments complemented by computational studies. The results support the involvement of ruthenium-hydride and ruthenium-vinylidene species as the key intermediates. They are best explained by a reaction pathway that consists of an oxidative addition of the amide, followed by insertion of a π-coordinated alkyne into a ruthenium-hydride bond, rearrangement to a vinylidene species, nucleophilic attack of the amide, and finally reductive elimination of the product.

Ruthenium-catalyzed stereoselective anti-Markovnikov-addition of thioamides to alkynes.

A catalyst system generated in situ from bis(2-methallyl)-cycloocta-1,5-diene-ruthenium(II) and a phosphine was found to efficiently catalyze the addition of thioamides to terminal alkynes with exclusive formation of the anti-Markovnikov thioenamide products. The stereoselectivity of the addition is usually high and controlled by the choice of the phosphine ligand, whereas the (E)-isomers are predominantly formed in the presence of tri(n-octyl)phosphine, the use of bis(dicyclohexylphosphino)methane preferentially leads to the formation of the (Z)-configured thioenamides.