Spectroscopic and quantum mechanical investigations of (2E)-3-(2H-1,3-benzodioxol-5-yl)-N-phenylprop-2-enamide using density functional theory method

The Fourier transform infrared (FTIR) and FT-Raman of (2E)-3-(2H-1,3-benzodioxol-5-yl)-N-phenylprop-2-enamide (2BNP2E) have been recorded in the regions 4000-100 and 4000-450cm-1, respectively. A complete assignment and analysis of the fundamental vibrational modes of the molecule have been carried out. The observed fundamental modes have been compared with the harmonic vibrational frequencies computed using DFT (B3LYP) method by employing 6-311++G(d,p) basis set. The vibrational studies have been interpreted in terms of potential energy distribution. The first order hyperpolarizability (β0) and related properties (α, μ and ∆α) of this molecular system are calculated using B3LYP/6-311++G(d,p) method based on the finite-field approach. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The results show that electron density (ED) in the σ* and π* anti-bonding orbitals and second-order delocalization energies (E(2)) confirm the occurrence of intramolecular charge transfer (ICT) within the molecule. Molecular electrostatic potential (MEP) and HOMO-LUMO energy levels have also been constructed. The thermodynamic properties of the title compound have been calculated at different temperature and the results reveal that the standard heat capacity C, entropy S and enthalpy changes H increase with rise in temperature

Spectroscopic characterization and electronic structure analysis of Linagliptin by DFT method

1172-1180The spectroscopic and electronic characterization of the molecule Linagliptin (LGP), one of the most important type-2 diabetes drugs, has been studied by the quantum mechanical method. The optimized molecular structure, electronic properties, dipole moment, rotational constants and important thermodynamic parameters of LGP molecule have been computed using HF (Hartree-Fock) and DFT (density functional theory) methods with 6-311++G (d,p) basis set. Spectroscopic properties such as FT-IR, Raman and absorption spectra are calculated in different solvents by the TD-DFT method and compared with the experimental data. The various types of intra-molecular interactions such as conjugative, hyper conjugative and other structural effects are analyzed from natural bonds orbitals of LGP. The relationship between linear polarizability and refractive index is used to describe the polarization behaviour of LGP in different solvents. The electronic charge density at different positions and reactivity descriptors of LGP are used in identifying the site of drug interaction. The various intra-molecular interactions are explained in terms of HOMO and LUMO energies. Mulliken charges and thermodynamic properties of LGP are also discussed

Vibrational and quantum chemical analysis of 3-methyl-2,6-diphenyl piperidin-4-one using HF and DFT methods

Characterization of 3-methyl-2,6-diphenylpiperidin-4-one (MDPO) by quantum chemical calculations and spectral techniques has been performed with spectroscopic investigations like FT-IR, FT-Raman and UV techniques. Molecular geometries, FT-IR spectrum (4000-400 cm-1) and FT-Raman spectrum (4000-100 cm-1) in solid phase was recorded. The structural and spectroscopic data of the molecule were obtained from HF and B3LYP with 6-311++G(d,p) levels using density functional theory(DFT). The stability and intra-molecular charge transfer have been analyzed by the detailed natural bond orbital (NBO) analysis. The charge transfer occurring in the molecule was verified and found to be stable from smaller energy gap by HOMO-LUMO analysis. Atomic population analysis reveals the percentage of electron distribution in s-and p-subshells. The first order hyperpolarizability of the investigated molecule has been studied theoretically. The calculated results were applied to simulated infrared and Raman spectra of the title molecule which show good agreement with observed spectra