Study and Calculation of the IR Spectrumfor Moleculecoumarin C14H12NO2F3 by Semi-Empirical Programs

This work aims to study potential energy and vibrational frequencies of a non-linear molecule (C522) using semi-experimental and MNDO-PM3 method, the geometric space shape for molecule was calculated through the initial and final matrix which includes the bonds lengths and the angle between bonds, surface angles and the charge of each atom in the molecules and from the curve of potential energy for molecule and depending on the change of the bond length (C15—C6) (C2—O3) (C15—F18) (C13—N12) (C14—H29) (C6═C1) (C2═O23) of the molecules versus the energy values obtained, and the total energy for molecules at equilibrium state was (-3915.10178 eV) and at equilibrium distance for each bond (1.53 A ), (1.37 A ), (1.35 A ), (1.48 A ), (1.10 A ), (1.34 A ) and (1.21 A ) respectively and from the potential energy curve, the dissociation energies were calculated for each bond are (5.69258 eV), (2.45383 eV), (5.90738 eV), (4.41122 eV), (7.53398 eV), (7.56607 eV) and (8.41981 eV) respectively. In addition, the energy values of the molecular orbitals are calculated including highest occupied molecular orbital (EHOMO), lowest unoccupied molecular orbital (ELUMO) and the energy gap for molecular (Egap) was equal to (7.38 eV). The vibrational frequencies of the molecule were also calculated when the vibrational frequencies for molecule at equilibrium state of vibration and the basic vibration modes were equal to 90 vibration mode.