Substituent Effect Transmission Power of Alkyl, Alkenyl, Alkynyl, Phenyl, Thiophenyl, and Polyacene Spacers

The larvicidal efficacy and mechanism of action of 5-Ethenyl-2,2'-bithiophene extracted from Echinops ritro on Aedes aegypti larvae

Herein, we focused on the larvicidal effects and potential mechanisms of 5-ethenyl-2,2'-bithiophene (5 EB), a compound isolated from Echinops ritro L. on Aedes aegypti larvae. Our results show that 5 EB exhibits pronounced larvicidal activity against A. aegypti larvae, with an LC50 = 0.24 mg/L, considerably lesser than that of the traditional insecticide, rotenone. Observations using fluorescence microscopy, electron microscopy, and imaging flow cytometry demonstrated that 5 EB targets the hemocytes of larvae, leading to the disruption of their intracellular membrane systems. This disruption leads to considerable damage to the cellular structure and function, leading to the death of test subjects. Note that additional investigation into the molecular mechanism of 5 EB's action was conducted using transcriptomic analysis. Both GO and KEGG enrichment analyses reported that the differentially expressed genes were predominantly associated with membranes, lysosomes, and catalytic activities. To summarize, this study provides new options for developing new, environmentally friendly, plant-based larvicides for mosquito control.

Unraveling the Push-Pull Effect in Acenes, Polyenes and Polyynes

Substituent effects (SEs) are fundamental for predicting molecular reactivity, while polyene, polyyne and acene derivatives are precursors to compounds with diverse applications. Computations were performed for Y-R-X systems, where reaction sites Y=NO2 and O- , substituents X=NO2 , CN, Cl, H, OH, NH2 , and spacers R=polyene, polyyne (n=1-5, 10 repeating units) and acene (up to tetracene). The cSAR (charge of the substituent active region) approach allowed to present, for the first time, quantitative relations describing the spacer's electron-donating and withdrawing properties as a function of n and the spacer type. The electronic properties of the X substituents depend on the type of spacer, its length and the Y group, which is an example of the reverse SE. To describe how the SE between Y and X weakens with n, two approaches were compared: cSAR and SESE (SE stabilization energy). The EDDB (electron density of delocalized bonds) characterize changes in electron delocalization in spacers due to the SE. A new approach - EDDB differential maps - allow to extract the effect of X substitution on the electron delocalization. The charges at spacer's C atoms correlate with cSAR; changes in the slopes confirm the charge transfer by resonance.

Substituent Effects from the Point of View of Energetics and Molecular Geometry in Acene, Polyene, and Polyyne Derivatives

The substituent effect (SE) is one of the most important topics in organic chemistry and related fields, and Hammett constants (σ) are commonly used to describe it. The results of the computational studies carried out for Y-R-X systems (reaction sites Y = NO₂, O^-; substituents X = NO₂, CN, Cl, H, OH, NH₂; spacers R = polyene, polyyne, acene with n = 1-5 repeatable units) show that the substituent properties depend significantly on n, the type of R, and Y. Results of the analysis of the substituent effect stabilization energy and geometrical parameters of the Y-R-X systems reveal that (i) the SE strength and its inductive and resonance components decay with the increase in spacer length, its weakening depends on the Y and R type; quantitative relations describing decay are presented; (ii) the ratio between inductive and resonance effect strength changes with n and depends on Y; (iii) differences in the substituents' properties are examples of reverse SE; (iv) in general, structural parameters are mutually well correlated as well as with the SE descriptors; (v) due to the strong O^- resonance effect, the changes in π-electron delocalization within R are well correlated with the SE strength only for Y = O^- systems.