Molecular structure, vibrational, UV, NMR, hyperpolarizability, NBO and HOMO–LUMO analysis of Pteridine2,4-dione

The FTIR and FT-Raman spectra of Pteridine2,4-dione has been recorded in the region 4000–450 and 4000–100 cm−1, respectively. The tautomeric stability, optimized geometry, frequency and intensity of the vibrational bands of Pteridine2,4-dione were obtained by the density functional theory (DFT) using 6-311++G(d,p) basis set. The harmonic vibrational frequencies were calculated and the scaled values have been compared with experimental FTIR and FT-Raman spectra. The observed and the calculated frequencies are found to be in good agreement. The 1H and13C NMR spectra chemical shifts of the molecule were also calculated using the gauge independent atomic orbital (GIAO) method. The theoretical UV–Vis spectrum of the compound using CIS method and the electronic properties, such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within molecule. The first order hyperpolarizability (β0) of these novel molecular system and related properties (β, α0 and Δα) of Pteridine2,4-dione are calculated using DFT/6-311++G (d,p) method on the finite-field approach. The Mulliken charges, the values of electric dipole moment (μ) of the molecule were computed using DFT calculations. The change in electron density (ED) in the σ* antibonding orbitals and stabilization energies E(2) have been calculated by natural bond (NBO) analysis to give clear evidence of stabilization originating in the hyper conjugation of hydrogen-bonded interactions.

Molecular structure of Pteridine2,4-dione was studied using B3LYP/6-311++G**. Spectroscopic studies were examined by FT-IR and FT-Raman techniques. The complete assignments are performed on the basis of total energy distribution. HOMO–LUMO energies, absorption wavelength and excitation energies were calculated.Figure optionsDownload as PowerPoint slideHighlights
► Different tautomeric forms of Pteridine2,4-dione with their relative energies have been predicted.
► Spectroscopic properties were examined by FT-IR, FT-Raman, NMR and UV spectra.
► The complete vibrational assignments are made on the basis of the total energy distribution (TED).
► NBO analysis and HOMO and LUMO energies are predicted.