The Spectroscopic (FT-IR, FT-Raman, NMR & UV-Vis) and first order hyperpolarizability, Homo and Lumo analysis of Maleic anhydride By HF and DFT Methods

In this work, experimental and theoretical study on the molecular structure and the vibrational spectra of Maleic anhydride is presented. The vibrational frequencies of the title compound were obtained theoretically by HF and DFT calculations employing the standard 6-311++G(d,p) basis sets for optimized geometry and were compared with Fourier transform infrared spectrum (FTIR) in the range of 100–4000 cm and with Fourier Transform Raman spectrum in the range of 100–4000 cm. Complete vibrational assignments, analysis and correlation of the fundamental modes for the title compound were carried out. The vibrational harmonic frequencies were scaled using scale factor, yielding a good agreement between the experimentally recorded and the theoretically calculated values. Moreover, C NMR and H NMR were calculated by using the gauge independent atomic orbital (GIAO) method with B3LYP methods and the 6311++G(d,p) basis set and their spectra were simulated and the chemical shifts linked to TMS were compared. A study on the electronic and optical properties; absorption wavelengths, excitation energy, dipole moment and frontier molecular orbital energies were carried out. The kubo gap of the present compound was calculated related to HOMO and LUMO energies which confirm the occurring of charge transformation between the base and ligand. Besides frontier molecular orbitals (FMO), molecular electrostatic potential (MEP) was performed. The NLO properties related to Polarizability and hyperpolarizability based on the finite-field approach were also discussed.