Modeling of multifunctional donor-bridge-acceptor 4,6-di(thiophen-2-yl)pyrimidine derivatives: a first principles study.

We have modeled multifunctional compounds by pi-elongation and push-pull strategy from the 4,6-di(thiophen-2-yl)pyrimidine. The ground state geometries have been optimized by density functional theory while excited state geometries were optimized by time dependent density functional theory (TDDFT). Structure-property relationship, electronic, optical and charge transfer properties (ionization potential, electron affinity and reorganization energies) were computed and discussed. By TDDFT absorption and emission have been calculated. The computed parameters were compared with available experimental data. The long-range corrected functional (LC-BLYP) is overestimating the highest occupied and lowest unoccupied molecular orbital energies, energy gaps while underestimating the absorption and fluorescence wavelengths. The B3LYP is good to reproduce the experimental data. The intra-molecular charge transfer has been observed from highest occupied molecular orbitals to lowest unoccupied molecular orbitals. The strong electron withdrawing and electron donor groups efficiently reduce the energy gaps. The decrease injection barrier and smaller reorganization energies are revealing that our designed derivatives would be efficient hole as well as electron transfer materials. These derivatives would be good light emitters e.g. blue, green, orange, red and near IR. The predicted values showed that the designed derivatives would be efficient for the organic field effect transistors, photovoltaics and light emitters.