Experimental and theoretical studies on the structure, electronic and vibrational spectra of o/p -hydroxybenzylidene- o/p -toluidines (original) (raw)

Orbital Analysis of Natural Bonds, Calculations of the Functional Theory of Density Time-Dependent and Absorption Spectral of a Series of Rhodanine Derivatives

Mediterranean Journal of Chemistry

In this work, the density functional theory (DFT) method at the B3LYP/6-31 + G (d, p) level has used to determine the optimization of five rhodanine derivatives. The stability of the derivatives (7a-7e) of 5-arylidene rhodanine, the hyperconjugative interactions, the delocalization of the atomic charges was analyzed with the analysis of the Natural Bond Orbital (NBO). The electronic structures were discussed and the relocation of electronic density was determined. Molecular Electrostatic Potential (MEP), local density functional descriptors, border molecular orbitals and absorption spectrum were studied. Through the local Fukui reactivity indices, the carbon of the carbonyl group (C = O) is the preferential site of the nucleophilic attack and the sulfur atom linked to the trigonal carbon (C = S) is the preferential site of electrophile attack. Analysis of the global descriptors revealed that compound 7c is the most reactive with an energy difference between the frontier orbitals of ...

Investigation on vibrational spectral activity and theoreticalcomputation of an anticancer drug 1-(p-toluenesulfonyl) imidazole

INTERNATIONAL CONFERENCE ON ADVANCES IN MATERIALS, COMPUTING AND COMMUNICATION TECHNOLOGIES: (ICAMCCT 2021), 2022

Vibrational spectral investigation and DFT computation have been performed on the anticancer drug 1-(ptoluenesulfonyl) imidazole (1PTSI). The structural parameters, intermolecular interactions and vibrational wavenumbers of the title molecule have been analysed with the help of B3LYP method. A detailed interpretation of the IR and Raman spectra of 1PTSI have been reported and analyzed. Vibrational modes of the title compound have been done on the basis of the potential energy distribution (TED) using VEDA software. The molecular electrostatic potential mapped onto total density surface has been obtained.The possible intramolecular interactions such as ICT, hyperconjucative interactions have been exposed by natural bond orbital analysis. The analysis of HOMO and LUMO gives an idea of the delocalization. The energy gap between HOMO and LUMO is found to be low and indicates electron transport in the molecule and thereby bioactivity. Effective docking of the drug molecule with different protein also enhances its bioactive nature.

Vibrational spectroscopic study of o-, m- and p-hydroxybenzylideneaminoantipyrines

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2010

Three structurally similar antipyrine derivatives of o-hydroxybenzylideneaminoantipyrine (o-HBAP), mhydroxybenzylideneaminoantipyrine (m-HBAP) and p-hydroxybenzylideneaminoantipyrine (p-HBAP) were characterized by FT-IR, FT-Raman experimental techniques and density functional theoretical (DFT) calculations. The comparisons between the calculated and experimental results covering molecular structures, assignments of fundamental vibrational modes and thermodynamic properties were investigated. The optimized molecular geometries agree well with the corresponding experimental values by comparing with the XRD data. The comparisons and assignments of the vibrational frequencies indicate that the experimental spectra also coincide satisfactorily with those of theoretically simulated spectrograms except the hydrogen-bond coupling infrared vibrations, and compounds can be distinguished by the IR and Raman spectra due to the differences of the hydroxyl-substituted positions and molecular packing, and the strong Raman scattering activities of the compounds are tightly relative to the molecular conjugative moieties linked through the Schiff base imines. The thermodynamic functions and their correlations with temperatures were also obtained from the theoretical harmonic frequencies.

A combined theoretical and experimental study on the structure, vibrational, and electronic properties of antiparkinsonian drug safinamide

SN applied sciences, 2020

In this work, structural, electronic, topological, and electronic and vibrational spectra of antiepileptic and antiparkinsonian drug safinamide (two enantiomers and their mesylate salt) were investigated with the DFT/TD-DFT methodology in gas phase and PCM solvent model. The absorbance maximum of safinamide was found at 227 nm, and the computed maximum transition occurred at 226 nm, which was assigned to π → π* transitions due to the chromophores C=C, C=O and C=N bonds. Electrostatic potential maps of all studied molecules revealed that the C=O group of (S)-enantiomer was more nucleophilic than the remaining molecules. Topological analysis suggested that an N-H intramolecular hydrogen bond especially in solution, and the NBO study showed a clear instability and strong ionic character of the salt. The lower electrophilicity and nucleophilicity indexes for the (S)-enantiomer than for the (R)-enantiomer, the higher reactivity it shows. At the same time, it shows higher activity as inhibitor of monoamine oxidase B. The force fields and the complete assignment of the 117 vibration normal modes of the enantiomers and 144 vibration normal modes of the mesylate salt are reported. The predicted infrared, Raman, 1 H-NMR, UV-visible, and ECD spectra were in reasonable agreement with the corresponding experimental ones. In addition, the interaction with monoamine oxidase was evaluated. This study provides a structural, vibrational, and electronic characterization of the drug through theoretical insights that will contribute to further research of the biological interaction mechanism.

Electronic structure investigations of 1-amino-2,6-dimethylpiperidine by NMR spectral studies by ab initio and DFT calculations

Indian Journal of Pure & Applied Physics, 2017

In this work, a combined experimental and theoretical study on molecular structure, vibrational spectra of 1-amino-2,6-dimethylpiperidine (ADP) has been reported. The FTIR and FT-Raman spectrum have been recorded in the region 4000-400 cm -1 and 3500-50 cm -1 , respectively. The molecular geometry, harmonic vibrational frequencies and bonding features of ADP have been calculated by using ab initio /HF and density functional theory/B3LYP methods with 6-31+G(d,p) basis set. A detailed interpretation of the FTIR, FT-Raman, NMR spectra of ADP has also been reported. Natural bond orbital analysis has been carried out to explain the charge transfer or delocalization of charge due to the intra-molecular interactions. Energy of the highest occupied molecular (HOMO) orbital and lowest unoccupied (LUMO) molecular orbital have been predicted.

Vibrational dynamics and molecular structure of 1H- and 3H-1,2,3-triazolo[4,5-b]pyridine and its methyl-derivatives based on DFT chemical quantum calculations

Chemical Physics, 2007

Molecular structure, vibrational energy levels and potential energy distribution of 1H-1,2,3-triazolo[4,5-b]pyridine and 3H-1,2,3-triazolo[4,5-b]pyridine as well as 1H-and 3H-tautomers of 5-methyl-1,2,3-triazolo[4,5-b]pyridine, 6-methyl-1,2,3-triazolo[4,5-b]pyridine and 7-methyl-1,2,3-triazolo[4,5-b]pyridine have been determined using density functional theory (DFT) at the B3LYP/6-31G(d,p) level. In order to obtain good fitting with the experimental values the calculated frequencies have been scaled using the scaling factors 0.96 and 0.975 in the 2800-3500 and 1000-1700 cm À1 region, respectively. The role of the hydrogen bond formation in the stabilization of the structure of the studied triazolo[4,5-b]pyridines has been discussed. The substitution place of the methyl group at the pyridine ring influences the proton position of the NH group at the triazole unit. The 5-and 7-methyl substitution leads to the 3H-tautomeric form whereas the 6-methyl substitution gives the mixture of 1H-and 3H-tautomers.