Ground and excited states of neutral and cationic thieno[3,2-b]thiophene: A DFT study
Abstract Geometry and excitation energy of the ground and low lying singlet excited states together with the ground state aromaticity of isomers of neutral and cationic thieno[3,2- b ]thiophene (TT) are studied by using density functional theory (DFT) and time dependent density functional theory (TD-DFT). Excitation leads to structural distortion in all the four isomers. Excitation wavelengths of the four isomers differ considerably. Aromaticity of ground state structures is quantified in terms of Nucleus Independent Chemical Shift (NICS) and Harmonic Oscillator Model of Aromaticity (HOMA). Plots of the chemical shifts and corresponding out of plane components as a function of the distance from plane of the molecule are also obtained.