Molecular Structure, Vibrational Spectra and Chemical Shift Properties of C12H9ClO4 and C2H9BrO4 Crystals by Density Functional Theory and ab initio Hartree-Fock Calculations

The molecular geometry, vibrational spectra, and guage including atomic orbital (GIAO), individual gauges for atoms in molecules (IGAIM), and continuous set of guage transformations (CSTG) H-1 and C-13 chemical shift values of ethyl 6-chloro-2-oxo-2H-chromene-3-carboxlate (C12H9ClO4-(I)) and ethyl 6-bromo-2-oxo-2H-chromene-3-carboxylite (C12H9BrO4-(II)) in the ground state have been Calculated by Using the Hartree-Fock (HF) and density functional method (B3LYP) with 63 31G+(d,p) basis set. The results of the optimized molecular structure are presented and compared with the experimental X-ray diffraction. The computed vibrational frequencies were used to determine the types of molecular motions associated with the spectra of the experimental hands observed. Also, calculated H-1 and C-13 chemical shift values were compared with the experimental ones