Role of molecular geometry, valence charge distribution and vibrational modes in bioactivity of cyclodiene insecticides

Abstract

Fourier transform infrared spectral measurement and complete normal mode calculations have been carried out for heptachlor and wedge modes have been identified. In addition, valence charge distributions have been obtained for aldrin, endrin, heptachlor, beta-endosulfan, cis-chlordane, trans-chlordane, photo-cis-chlordane and photo-trans-chlordane using CNDO/2 (complete neglect of differential overlap) molecular orbital calculations. A toxicity parameter has been defined as the product of the charge distribution and surface area of the corresponding active wedges, depending on the interacting structural features. The variation of this toxicity parameter is generally in order and in agreement with the reported measurements based on the corresponding order of observed LD50 values. Because of the structural features, the toxicity in these cases is a surface phenomenon rather than a volume effect as in the case of Gammexane, wherein the insecticide binds itself to membrane channels. Because the biological activity is a dynamic rather than a static phenomenon, it is expected that the normal modes involving the wedge atoms play an important role.

Functionalization of Ag nanoparticles with the bis-acridinium lucigenin as a chemical assembler in the detection of persistent organic pollutants by surface-enhanced Raman scattering

“…ES develops its toxicity mainly on the nerve cell membranes, by inhibiting the transport of cations as Ca 2+ , K + , Na + and Mg 2+ across the membranes [32][33][34]. It is possible to distinguish two main moieties within their structures: the chlorinated part, which constitutes the active wedge of the molecule bringing the large excess of charge responsible for the interaction with electron receptors [35], and the sulfonic ester side, which acts as an anchor supporting the altering action of the pesticide [36]. The unchlorinated moiety strongly affects the relative toxicity of the insecticide and as a proof of that it is reported that the ␣-ES isomer (Fig.…”

Self-assembly of α,ω-aliphatic diamines on Ag nanoparticles as an effective localized surface plasmon nanosensor based in interparticle hot spots

“…These bands are mainly assigned to C-Cl stretching motions and constituted an actual fingerprint of this molecule, which is completely different from the vibrational spectrum of other related polychlorinated molecules. [52][53][54] The comparison with the Raman of solid aldrin (Fig. 14d) reveals some differences due to the interaction with AD 8 .…”

α,ω-Aliphatic Diamines as Molecular Linkers for Engineering Ag Nanoparticle Clusters: Tuning of the Interparticle Distance and Sensing Application

“…7). These bands are mainly assigned to C-Cl vibrations [56,59] and are sensitive to the molecular conformation of the pollutant [60]. In particular, the intense feature at about 400 cm −1 can be attributed to the C-Cl stretching of the Cl-C=C-Cl fragment (i.e., the most electron-donor group of the insecticide molecule), whereas the C-Cl modes appearing at lower frequencies can be assigned to vibrations involving C atoms of less polar portions of the structure [60].…”

“…Figure 5 shows the structure of the insecticides studied in this paper: α-ES, β-ES, and ALD. It is possible to distinguish two main moieties within their structures: (1) the chlorinated part, which constitutes the active wedge of the molecule bringing the large excess of charge responsible for the interaction with electron receptors [55], and (2) the unchlorinated part, which acts as an anchor supporting the altering action of the insecticide [56] on the cell membranes. Therefore, even the unchlorinated moiety strongly affects the relative toxicity of the insecticide, and as a proof of that, it is reported that the α-endosulfan displays much higher insecticidal property than the β-isomer [57].…”