Solvent Effects on the Structural, Electronic, Non-Linear Optical and Thermodynamic Properties of Perylene Based on Density Functional Theory

Perylene (C20H12) is an important member of the polycyclic aromatic hydrocarbons (PAHs) that has a wide applications such as organic photovoltaic cells, field effect transistors and biosensors. Optimized bond lengths and bond angles, HOMO-LUMO energy gap, global chemical indices, total energy, nonlinear optical and thermodynamic properties of Perylene in the gas phase and in solvents (water, chloroform, benzene and acetone) were obtained based on Density Functional Theory with B3LYP/6-311++G(d,p) basis set. All the computations were carried out using Gaussian 03 package and revealed that the solvents have an effect on the optimized parameters. It was observed that the bond lengths increase with an increase in the polarity of the solvents, while the bond angles were found to increase as the polarity of the solvents decreases. Perylene molecule was found to have a higher stability in the gas phase with HOMO-LUMO energy gap of 2.9935eV. The HOMO and HOMO-LUMO energy gap were found to increase with an increase in polarity of the solvents. The molecule was found to be harder and less reactive in the gas phase with chemical hardness of 1.4968eV. The maximum value of ionization potential 5.3227eV and minimum value of electron affinity 2.2757eV were obtained in water and gas phase respectively, as such it is difficult to remove an electron from the molecule in water to form an ion and it is also difficult to add an electron to the molecule in gas phase. The ground state total energy of the molecule was found to increase with an increase in polarity of the solvents. Similarly, the chemical hardness, chemical softness, electronegativity, chemical potential and electrophilicity index were found to increase with an increase in the dielectric constant of the solvents. In the non-linear optical (NLO) properties calculations, it was observed that Perylene is a neutral molecule. It was found that the specific heat capacity of perylene increases with an increase in the polarity of the solvent while the entropy and the zero-point vibrational energy of the molecule decreases as the polarity of the solvent increases. In the non-linear optical properties calculations, it was found that the polarizability (⟨α⟩) of Perylene increases with decrease in the polarity of the solvents and the anisotropic polarizability (∆α) of Perylene increase with an increase in the polarity of the solvents. In the Natural Bond Orbital (NBO) analysis, high intensive interaction between donor and acceptor electrons of Perylene was observed in chloroform due to to large stabilization energy of 4.49Kcal/mol. The result shows that careful selection of the solvents and basis sets can tune the frontier molecular molecular orbital energy gap.