Study The Spectral and Thermal Properties of The Molecule Tetracene (C18-H12) by Using Semi Empirical Quantum programs

Abstract

Abstract The aim of this study is to determine the spectral properties of the Tetracene molecule (C18H12) using the Semi-empirical quantum programs (Hyper Chem8.0, WinMopac7.21) by (MNDO-PM3) method ( Modified Neglect of Differential Overlap-Parameterization Model3) The study envelope computation of the space geometry of the Tetraene molecule was calculated using the initial and final matrices, including the length, the angle between the bonds, the angle of the dipole, and the charge of each atom in the Tetracene molecule, The total energy, binding energy, electronic energy, core-core repulsion, ionization potential, molecular weight, moment of inertia, and dipole moment of the molecule were also calculated The curved potential energy of each molecule has been plotted as it is adopted to vary the length of the bonds, (C1-H19) and (C1-H15) in the Tetracene molecule compared to the result of the total energy values of Tetracene in equilibrium. In addition to the potential energy curve, the dissociation energy of spectroscopy was calculated for molecule and the molecular orbit including ELUMO equal to (-1.353), EHOMO equal to (-7.87eV), Egap equal to (6.517 eV) of Tetracene. Likewise, the vibration frequencies of the Tetracene molecule were obtained in the infrared region and electron transmission in the UV region. Some thermal properties (thermodynamics) of Tetracene were also calculated, including heat of formation, entropy, heat capacity, enthalpy and, gibbs free energy, at a temperature (298K), the value of the Tetracene molecule was equal to (84.445)kcal.mol-1, (114.6487)Cal.mol-1.K-1, (54.8085)Cal.mol-1.K-1,(8484.7728)Cal.mol-1 (-25716.70)Cal.mol-1 respectively. The results of the theoretical study agreed with the experimental results and almost with the previous research.