Spectroscopic (FT-IR, FT-Raman and NMR) and computational studies on 3-methoxyaniline

Comparative study of physico-chemical properties of some molecules from Khaya Grandifoliola plant

The three molecular compounds: A (17-epi-methyl-6-hydroxylangolensate), B (7-deacetoxy-7-oxogedunin) and C (7-deacetoxy-7R-hydroxygedunin) isolated from Khaya Grandifoliola, a plant of the Meliaceae family, able to protect the normal human hepatocyte cell line against paracetamol-induced hepatotoxicity were studied using HF and DFT methods. It appears from this study that compound A has the greatest capacity of donating charges while compound B, which is the most reactive compound according to the HOMO-LUMO energy gap, has a greater capacity to accept charges. From the calculation of certain donor-acceptor parameters, it comes out that compound C is the most easily oxidizable substance and therefore the most effective free radical scavenger. Of the three molecular compounds, A is the best antioxidant while B is the best antireductant. From the values ​​obtained for compounds A, B and C, we concluded that these compounds are better antioxidants than β-carotene and better antireductants than vitamins A, C and E. Compounds A, B, and C are less efficient electron acceptors than fluorine and more efficient electron donors than Na. The calculation of certain thermodynamic parameters shows that, the molecular compounds studied can easily bind to a biomolecular complex. UV-vis spectrum analysis shows that the maximum peaks are located in the UV region between 230 and 356 nm. The nonlinear optical parameters along with vibrational frequencies of these compounds were calculated and compared.

Experimental and theoretical investigation on the molecular structure, spectroscopic and electric properties of 2,4-dinitrodiphenylamine, 2-nitro-4-(trifluoromethyl)aniline and 4-bromo-2-nitroaniline

2,4-Dinitrodiphenylamine (I), 2-nitro-4-(trifluoromethyl)aniline (II) and 4-bromo-2-nitroaniline (III) have been investigated by DFT and experimental FTIR, Raman and UV-Vis spectroscopies. The gas-phase molecular geometries were consistent with similar compounds already reported in the literature. From the vibrational analysis, the main functional groups were identified and their absorption bands were assigned. Some differences were found between the calculated and the experimental UV-Vis spectra. These differences were analyzed and explained in terms of the TD-DFT/B3LYP limitations, which were mainly attributed to charge-transfer (CT) effects. These findings were in agreement with previous works, which reported that TD-DFT/B3LYP calculations diverge from experimental results when the electronic transitions involve CT. Despite this, TD-DFT/B3LYP calculations provided satisfactory results and a detailed description of the electronic transitions involved in the absorption bands of the UV-Vis spectra. In terms of the NLO properties, it was found that compound (I) is a good candidate for NLO applications and deserves further study due to its good β values. However, the β values for compounds (II) and (III) were negatively affected compared to those found on o-nitroaniline.

The spectroscopic and quantum chemical studies of 3,4-difluoroaniline

Spectroscopic and structural investigations of 3,4-difluoroaniline molecule are presented by using experimental (FT-IR, FT-Raman, (1)H and (13)C NMR, and UV-Vis) techniques and theoretical (DFT approach) calculations. FT-IR and FT-Raman spectra of 3,4-difluoroaniline molecule are recorded in the region 4000-400cm(-1) and 3500-10cm(-1) in the liquid phase, respectively. The NMR chemical shifts ((1)H and (13)C) are recorded in chloroform-d solution. The UV absorption spectra of 3,4-difluoroaniline dissolved in ethanol and water are recorded in the range of 200-400nm. Experimental results are supported with the following theoretical calculations; the optimized geometry and vibrational (FT-IR and FT-Raman) spectra are carried out by DFT (B3LYP)/6-311++G(d,p) basis set calculations. The nuclear magnetic resonance spectra ((1)H and (13)C NMR) are obtained by using the gauge-invariant atomic orbital method. Moreover, electronic characteristics, such as HOMO and LUMO energies, density of state diagrams, and molecular electrostatic potential surface are investigated. Nonlinear optical properties and thermodynamic features are also outlined theoretically. An excellent correlation of theoretical and experimental results provides a detailed description of the structural and physicochemical properties of the molecule. Thus, this work leads to a deep understanding of the characteristics of di-substituted aniline derivatives.

Quantum chemical studies on structural, vibrational, NBO and hyperpolarizability of N-(1,1-Dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid

The FTIR and FT-Raman spectra of N-(1,1-Dimethyl-2-hydroxyethyl)-3-amino-2-hydroxypropanesulfonic acid were recorded in the regions 4000-400cm(-1) and 4000-50cm(-1) respectively. The structural and spectroscopic data of the molecule in the ground state were calculated using Hartee-Fock and density functional method (B3LYP) with the correlation consistent-polarized valence double zeta (cc-pVDZ) basis set. The most stable conformer was optimized and the structural and vibrational parameters were determined based on this. With the observed FTIR and FT-Raman data, a complete vibrational assignment and analysis of the fundamental modes of the compound were carried out. Thermodynamic properties and Mulliken charges were calculated using both Hartee-Fock and density functional method using the cc-pVDZ basis set and compared. The calculated HOMO-LUMO energy gap revealed that charge transfer occurs within the molecule. (1)H and (13)C NMR chemical shifts of the molecule were calculated using Gauge Including Atomic Orbital (GIAO) method and were compared with experimental results. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using Natural Bond Orbital (NBO) analysis. The first order hyperpolarizability (β) and Molecular Electrostatic Potential (MEP) of the molecule was computed using DFT calculations. The electron density based local reactivity descriptor such as Fukui functions were calculated to explain the chemical reactivity site in the molecule.

Spectroscopic and quantum chemical studies on bromopyrazone

In this study, the FT-IR, micro-Raman and UV-vis. spectra of bromopyrazone molecule, C10H8BrN3O, (with synonym,1-phenyl-4-amino-5-bromopyridazon-(6) or 5-amino-4-bromo-2-phenyl-3(2H)-pyridazinone) were recorded experimentally. The molecular structure, vibrational wavenumbers, electronic transition absorption wavelengths in ethanol solvent, HOMOs and LUMOs analyses, molecular electrostatic potential (MEP), natural bond orbitals (NBO), nonlinear optical (NLO) properties and atomic charges of bromopyrazone molecule have been calculated by using DFT/B3LYP method with 6-311++G(d,p) basis set in ground state. The obtained results show that the calculated vibrational frequencies and UV-vis. values are in a good agreement with experimental data.