Molecular geometry and vibrational studies of 3,5-diamino-1,2,4-triazole using quantum chemical calculations and FT-IR and FT-Raman spectroscopies

Vibrational characterization of the pesticide molecule Tebuconazole

Pesticide use worldwide exhibits a positive effect on agricultural production while it may negatively affect organisms living in soil, water or the air. Importantly, numerous negative health effects also occur in humans exposed to (accumulated) pesticides or their metabolites over a long period of time. To prevent both environmental catastrophes and adverse human health impacts, initial studies of the selected pesticides need to be performed together with the constant post-approval control; risk assessment analysis and on site monitoring have to be continuously carried out. Given this, Raman spectroscopy, especially surface-enhanced Raman spectroscopy (SERS), during the last decade has become a powerful analytical technique since it can offer quick, selective, and in situ detection of selected pollutants found in analyzed samples at very low concentrations. Moreover, the structural changes caused by the pollutant-biomacromolecule interaction can also be recognized in the molecule-specific Raman spectral signatures of biomolecules. In this study, we report a vibrational characterization of the fungicide molecule Tebuconazole (TB) which is listed to be a possible carcinogen. Even though its international and common use there is no evidence about the use of Raman/SERS spectroscopy to detect it sensitively and selectively as well as to analyse its impacts on biological systems. Therefore, we have recorded and calculated Raman and infrared spectra of TB. Furthermore, SERS spectra of TB were also registered and comprehensively analysed in view of the employed SERS substrates, dependence on the excitation wavelengths and pH of the analysed molecular systems. The molecule of TB interacts preferentially through the triazole moiety with the colloidal metal nanoparticles (NPs) whereas the silver NPs prepared by reduction of silver nitrate with hydroxylamine hydrochloride resulted to be the most effective ones. Consequently, the limit of detection was determined to be 1.4 μM≈430 ppb. The present paper thus could serve significantly for further investigations focused on both conducting vibrational analyses of structurally related molecules as well as providing a more precise explanation of the mechanism of action of TB and its influence on biological macromolecules.

Microencapsulation of Osmanthus essential oil by interfacial polymerization: Optimization, characterization, release kinetics, and storage stability of essential oil from microcapsules

In this paper, the interface polymerization method was used to prepare Osmanthus essential oil microcapsules. The optimal preparation process of Osmanthus essential oil microcapsules was explored as follows: the dosage ratio of Osmanthus essential oil to N100 was 6:1, the reaction temperature was 70°C, and the reaction time was 2 h. The encapsulation efficiency of Osmanthus essential oil microcapsules could reach 80.31%. The particle size distribution, morphology, chemical structure, and thermal stability of the obtained microcapsules were characterized by laser particle size analyzer, scanning electron microscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. The release kinetics and storage stability experiments of the microcapsules were studied. The results showed that the average volume diameter of the microcapsules was 101.2 µm. The microcapsules were in the shape of full spheres, with a smooth surface, low viscosity, and high elasticity. Microencapsulation improved the thermal stability of Osmanthus essential oil and promoted the slow release of essential oil. The synthesized microcapsules showed good storage stability under refrigerated and dark conditions, which indicated that microcapsules had broad application prospects in food, medicine, and other fields. PRACTICAL APPLICATION: In this study, we prepared a polyurea membrane to encapsulate Osmanthus essential oil microcapsules by interfacial polymerization. The encapsulation conditions of the microcapsules were optimized and the structure of the microcapsules was characterized in this study. The results showed that microcapsules had a full spherical shape with a smooth surface, high elasticity, good sustained-release ability, good thermal stability, and storage stability. These properties indicated that microcapsules have good application prospects and can be used as a high-quality flavor with a long residual effect and high thermal stability for food and cosmetic scope.

Environment-dependent conformation investigation of 3-amino-1,2,4-triazole (3-AT): Raman Spectroscopy and density functional theory

In the paper, diverse tautomers of 3-amino-1,2,4-triazole (3AT) in solid and polar solvent have been explored by FT-IR, FT-Raman and 488nm Raman experiments combing with quantum chemical theoretical calculation using PCM solvent model and normal mode analysis. The vibrational spectra prefer the 3-amino-1,2,4-2H-triazole (2H-3AT) dimer in solid, while in a polar solvent 3AT is apt to the 3-amino-1,2,4-2H-triazole (2H-3AT) monomer. The significant wavenumber difference and Raman intensity patterns in solid and different solvents are induced by hydrogen bond perturbation along >NH⋯N≤ hydrogen bonds on five-membered N-heterocyclic ring. The ground state proton transfer reaction mechanism along the five-membered N-heterocyclic ring is supported by intermolecular hydrogen bonding between 3AT and protonic solvent molecules.

High pressure studies of Ni3[(C2H5N5)6(H2O)6](NO3)6·1.5H2O by Raman scattering, IR absorption, and synchrotron X-ray diffraction

Molecular structure (a) and packing diagram (b) of 1. The green, grey, blue, red, and white spheres denote Ni, C, N, O, and H atoms, respectively.

Metal based new triazoles: their synthesis, characterization and antibacterial/antifungal activities

A series of new triazoles and their oxovanadium(IV) complexes have been synthesized, characterized and evaluated for antibacterial/antifungal properties. The new Schiff bases ligands (L(1))-(L(5)) were prepared by the condensation reaction of 3,5-diamino-1,2,4-triazole with 2-hydroxy-1-naphthaldehyde, pyrrole-2-carboxaldehyde, pyridine-2-carboxaldehyde, 2-acetyl pyridine and 2-methoxy benzaldehyde. The structures of the ligands have been established on the basis of their physical, spectral (IR, (1)H and (13)C NMR and mass spectrometry) and elemental analytical data. The prepared ligands were used to synthesize their oxovanadium(IV) complexes (1)-(5) which were also characterized by their physical, spectral and analytical data and proposed to have a square pyramidal geometry. The ligands and their complexes were screened for in vitro antibacterial activity against six bacterial species such as, Escherichia coli, Shigella flexneri, Pseudomonas aeruginosa, Salmonella typhi, Staphylococcus aureus, and Bacillus subtilis and for in vitro antifungal activity against six fungal strains, Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani, and Candida glabrata. Cytotoxic nature of the compounds was also reported using brine shrimp bioassay method against Artemia salina.

Molecular structure and vibrational study of diprotonated guanazolium using DFT calculations and FT-IR and FT-Raman spectroscopies

The purpose of this manuscript is to discuss our investigations of diprotonated guanazolium chloride using vibrational spectroscopy and quantum chemical methods. The solid phase FT-IR and FT-Raman spectra were recorded in the regions 4000-400cm(-1) and 3600-50cm(-1) respectively, and the band assignments were supported by deuteration effects. Different sites of diprotonation have been theoretically examined at the B3LYP/6-31G level. The results of energy calculations show that the diprotonation process occurs with the two pyridine-like nitrogen N2 and N4 of the triazole ring. The molecular structure, harmonic vibrational wave numbers, infrared intensities and Raman activities were calculated for this form by DFT/B3LYP methods, using a 6-31G basis set. Both the optimized geometries and the theoretical and experimental spectra for diprotonated guanazolium under a stable form are compared with theoretical and experimental data of the neutral molecule reported in our previous work. This comparison reveals that the diprotonation occurs on the triazolic nucleus, and provide information about the hydrogen bonding in the crystal. The scaled vibrational wave number values of the diprotonated form are in close agreement with the experimental data. The normal vibrations were characterized in terms of potential energy distribution (PED) using the VEDA 4 program.

FT-IR, FT-Raman, ab initio and DFT studies, HOMO-LUMO and NBO analysis of 3-amino-5-mercapto-1,2,4-triazole

The molecular vibrations of 3-amino-5-mercapto-1,2,4-triazole (AMT) have been investigated in polycrystalline sample, at room temperature, by Fourier transform infrared (FT-IR) and FT-Raman spectroscopies. A detailed vibrational spectral analysis has been carried out and assignments of the fundamental modes have been proposed on the basis of peak positions and relative frequencies, atomic charges, HOMO-LUMO energies and several thermodynamic properties in the ground state were calculated using ab initio Hartree-Fock (HF) and Density Functional Theory, (B3LYP) with 6-311G(d,p) and 6-311++G(d,p) basis sets. With the aid of scaling procedures, observed wave numbers in FT-IR and FT-Raman spectra were analyzed and assigned to different normal modes of the molecule. Most of the modes have wave numbers in the expected range. The theoretical IR and Raman spectra have also been constructed. Natural Bond Orbital (NBO) study explains charge delocalization of the molecule.