One-pot synthesis, FT-IR and density functional method (DFT) studies on N-benzyl-N-ethyl-N-[5-nitro-2-(1,1,3,3-Tetramethylbutylamino)-1-benzofuran-3-yl]amine

Raman and SERS spectra of thiamethoxam and the Ag3-thiamethoxam complex: an experimental and theoretical investigation

The insecticide thiamethoxam (TMX) is one of the most important neonicotinoid pesticides. The chromatographic methods currently employed to detect TMX require multiple operational steps. This study proposes a simple method that detects TMX via surface-enhanced Raman scattering (SERS) spectroscopy with Ag nanoparticles (NPs) as the SERS active substrate. Density functional theory (DFT) was used to calculate the structures and vibrational modes of the Ag- and Ag₃-TMX complexes at the B3LYP/6-311++G(d,p)(C,H,N)/LanL2DZ(Ag) level of theory. The results reveal that the atoms in the thiazole ring all lie in the same plane, while the six-membered ring is perpendicular to the thiazole ring. Data from both Ultraviolet-visible and Raman spectroscopy indicated that TMX bonds to Ag through its nitro group, vertically. A weak intramolecular (N22-O23…H26) hydrogen bonding and Ag-O bands shift N-O symmetrical vibration to down to lower wavenumber. This was supported by the appearance of a strong 866 cm^-1 band in the SERS spectrum assigned to the N-O symmetrical vibration coupled with the N-N stretching vibrational mode of different excitation wavelength. Notably, a good linear relationship was observed in the TMX concentration range 1.0 × 10^-6-1.0 × 10^-4mol·L^-1 (R² = 0.9667). SERS is an extremely simple and rapid technique that requires little sample for analysis.

Domino carbometalation/coupling reactions of N-arylpropiolamides: a novel and promising synthetic strategy toward stereocontrolled preparation of highly substituted 3-methyleneindolinones

3-Methyleneindolinone derivatives are important structural motifs found in many compounds of natural occurrence and pharmacological significance.

N-Propargylic β-enaminocarbonyls: powerful and versatile building blocks in organic synthesis

Nitrogen-containing heterocyclic compounds are not only prevalent in an extensive number of natural products and synthetic pharmaceuticals but are also used as building blocks in organic synthesis.

Exploring the binding mechanism of 5-hydroxy-3',4',7-trimethoxyflavone with bovine serum albumin: Spectroscopic and computational approach

The current study was carried out to investigate the binding mechanism of a potential flavonoid compound 5-hydroxy-3',4',7-trimethoxyflavone (HTMF) with bovine serum albumin (BSA) using ultraviolet-visible, fluorescence, circular dichroism (CD) spectral measurements along with molecular docking and molecular dynamics (MD) simulation. It was confirmed from fluorescence spectra that the intrinsic fluorescence of BSA was robustly quenched by HTMF through a static quenching mechanism. The number of binding sites (n) for HTMF binding on BSA was found to be about one. The thermodynamic parameters estimated from the van't Hoff plot specified that hydrophobic force was the predominant force in the HTMF-BSA complex and there also exist hydrogen bonds and electrostatic interactions. The effect of HTMF on the BSA conformation examined using CD studies revealed that there is a decrease in the helical content of BSA upon HTMF interaction. The results of molecular docking study shed light on the binding mode which exposed that HTMF bind within the hydrophobic pocket of the subdomain IIIA of BSA. The stability of HTMF-BSA complex with respect to free protein was analyzed from the molecular dynamic studies. The electronic structure analysis of HTMF was achieved by using density functional theory (DFT) calculations at B3LYP/6-31G** level to support its antioxidant role. The results of computational analysis are in good consistence with the experimental data and the present findings suggested that HTMF exhibits a good binding propensity to BSA protein which will be helpful for the drug design.

New route to 1,4-oxazepane and 1,4-diazepane derivatives: synthesis from N-propargylamines

N-Propargylamines are one of the most useful and versatile building blocks in organic synthesis that are successfully transformed into many significant N-heterocycles.

New page to access pyridine derivatives: synthesis from N-propargylamines

The pyridine is one of the simplest, yet most important N-heterocycles.

Computational studies on the anastrozole and letrozole, effective chemotherapy drugs against breast cancer

In this paper, computational studies were carried out on anastrozole and letrozole, chemotherapy drugs used against breast cancer. Optimization and frequency calculations were performed at B3LYP/6-31G (d) basis set and vibrational frequencies were assignment. Single point calculations were performed at DFT method with a hybrid functional B3LYP/6-311G (d, p) basis set. Theoretical NMR data were obtained at DFT method with a hybrid functional B3LYP/6-311G++ (2d, p) with GIAO (Gauge-Independent Atomic Orbital). IEF-PCM method was used as solvation model. NBO calculations were performed by the same basis set and calculation method with single point calculation. Global and localized reactivity parameters; fukui indices (f) chemical hardness (η), softness (S), chemical potential (μ), electronegativity (χ) and electrophilicity index (ω) were calculated. All computational parameters were compared with the experimental results obtained from the literature.

Experimental and DFT studies on the vibrational, electronic spectra and NBO analysis of thiamethoxam

Vibrational and electronic spectral measurements were performed for 3-(2-chloro-1,3-thiazol-5-ylmethyl)-5-methyl-1,3,5-oxadiazinan-4-ylidene(nitro) amine (thiamethoxam). Optimized geometrical structure and harmonic vibrational frequencies were calculated with ab initio RHF and DFT (B3LYP, CAMB3LYP, M06 and PBE1PBE) methods with 6-311++G (d, p) basis set. Complete assignments of the observed spectra were proposed. The absorption spectra of the compound were computed in gas-phase using TD-B3LYP/6-311++G (d, p) approach and H2O solution using PCM-TD-B3LYP/6-311++G (d, p) approach. The calculated results matched well with the experimental values. Temperature dependence of thermodynamic parameters in the range of 100-1000 K were determined. The bond orbital occupancies, contribution from parent natural bond orbital (NBO), the natural atomic hybrids was discussed.