Computational studies of vibrational spectra and molecular properties of 6-methyluracil using HF, DFT and MP2 methods

Abstract

Theoretical investigations of atomic charges, conformers, frontier molecular orbitals, molecular geometries, thermodynamic properties, hyperpolarizabilities and harmonic vibrational frequencies of 6-methyluracil (6MU) have been carried out using ab initio Hartree-Fock (HF), density functional theory (DFT) and second order Møller-Plesset (MP2) methods. All calculations were performed using the GAMESS-US program package with the basis sets 6-31G(d,p) and 6-311G(d,p). FT-IR and Raman spectra of 6MU were recorded in the regions 50-4000 cm -1 and 60-4000 cm -1 respectively. Optimized geometries were obtained using the global optimization procedure. The calculated structural parameters for two conformers of 6MU have been compared with experimentally observed values. The energy barrier ('E=ELUMO-EHOMO) between the HOMO and LUMO is predicted on the basis of theoretical calculations. The simulated TD-DFT spectrum has been compared with experimental electronic spectrum for 6MU. The calculated potential energy distribution (PED) values have been utilized to perform vibrational assignment of the infrared and Raman spectra.

Peculiarities of the Spatial and Electronic Structure of 2-Aryl-1,2,3-Triazol-5-Carboxylic Acids and Their Salts on the Basis of Spectral Studies and DFT Calculations

“…Density Functional methods (DFT) [26] were mainly used for the calculations, which provide adequate compromise between the computer time and power required for the computations and the desired chemical accuracy of the results. In biomolecules, DFT calculations have provided results which are quantitatively in good accordance with those raised at MP2 level [27,28], and even better for the vibrational wavenumber calculations [14]. The B3LYP/6-31G(d,p), M06-2X/6-31G(d,p) and MP2/6-31G(d,p) theoretical levels were used for geometry optimizations and NBO atomic charges computations [29], while the B3LYP/6-31G(d,p) was mainly used [30,31] in the calculation of the harmonic IR and Raman vibrational wavenumbers.…”

Electronic Structure, Nonlinear Optical Properties, and Vibrational Analysis of Gemifloxacin by Density Functional Theory

“…The most important ring stretching vibration is the ring breathing vibration at mode 90. In this mode, all bonds of the rings appear to stretch and contract in-phase with each other [33]. In the experimental infrared spectrum of gemifloxacin, this mode appears at 649 cm −1 .…”

Current advances in computer-aided design of electrochemical sensors: An analytical review

“…Some other computational activities were pointed towards calculating different molecular properties such as; partial charges, charge distribution, electrostatic potentials, strain, solvation, and binding energies. These properties are essential to be defined for a molecule to aid in searching molecular conformations, energy minimization, predicting molecular behavior in various chemical systems like the ability to bind to specific functional groups on macro-molecular targets or stability of some interactions in gas and solvated media, and in calculating the molecular orbitals that are essential in calculating the infrared or ultraviolet transitions for a molecule (Neese, 2009;Rasheed and Ahmad, 2011).…”