A theoretical study of the linear, nonlinear optical properties and conformational analysis of 3-phenylthiophene and its fluoro derivatives with torsional dependence

In this study, we have investigated the energies, dipole moments, HOMO-LUMO energy differences and polarizability values of 3-phenylthiophene and its fluoro-substitued derivatives as a function of the torsional angle. For each molecule, geometrical parameters have obtained using ab initio [Hartree-Fock (HF) and second-order Møller-Plesset (MP2)] and Density Functional Theory (DFT) with the 6-31++G∗∗ and 6-311++G∗∗ basis sets. The calculated physical quantities, such as electronic energy, dipole moment (μ), HOMO-LUMO energy differences (ΔE), polarizability (α) and hyperpolarizability (β) values are at the ground state geometry. The effect of the position of fluorine substituent on structural parameters, on dipole moments and on torsional potentials have been examined. The frontier molecular orbital calculations clearly show that there is an inverse relationship between HOMO-LUMO energy differences and their polarizabilities. We have also calculated λmax values from the HOMO-LUMO energy differences. Finally we have discussed the trends in the calculated torsional potentials, barrier heights, and energy differences between conformers and correlated them with selected structural parameters.