Electronic Structure and Non-Linear Optical Properties of Neutral and Ionic Pyrene and Its Derivatives Based on Density Functional Theory

Pyrene (C16H10) is an organic semiconductor suitable for the development of organic light emitting diodes (OLED), organic photovoltaic cells (OPV) and many other electronic components. Ionic and chlorination effects on electronic and non-linear optical properties of pyrene molecule have been investigated based on Density Functional Theory (DFT) using Becke’s three and Lee Yang Parr (B3LYP) functional with basis sets 6-311G and 6-311+G (d). Parameters such as minimum energy, bond lengths and angles, HOMO-LUMO energy gap, chemical reactivity descriptors, isotropic polarizability (α), anisotropy of polarizability (Δ∝), and total first hyper-polarizability (βtot)) for neutral and ionic forms were computed to determine the relative stability and reactivity of the molecules. All computations have been performed using Gaussian 03. The results showed that charging the molecule and the introduction of chlorine in the ring have changed the electronic and non-linear-optical properties of the molecule. It is revealed that cationic and anionic forms of 2-chloropyrene have smaller values of energy gap as 3.641eV and 0.078eV respectively compared to the neutral form which has 3.822eV showing a significant change in the energy gap. Addition of chlorine atom to the neutral molecule is less significant in changing the energy gap. Cationic form of 2-chloropyrene has hyperpolarizability value of 128.881a.u compared to 75.508a.u of the neutral form while anionic molecule has 27.515a.u which is below that of the neutral molecule. The computed results agreed with reported works. To this effect, charged Pyrene is considered to be a potential candidate over the neutral molecule for practical applications.