Electronic structure and charge-transport properties of symmetric linear condensed bis-benzothiadiazole derivatives

Abstract

The optimal geometries and electronic structures of fifteen symmetric linear condensed bis-benzothiadiazole derivatives were investigated using the density functional theory. Depending on the central core variation, the B3LYP energies of the lowest unoccupied molecular orbitals (LUMOs) varies from −2.66 eV to −4.77 eV. The interaction energies and electron drift mobilities were evaluated for model parallel-stacked and parallel-displaced dimer configurations at room temperature using Marcus theory and Einstein relation. The presented theoretical results indicate contradictory role of the pyrazine moiety fused to benzene or p-benzoquinone forming the central molecular core. These model compounds exhibit the highest electron drift mobilities, although the air stability could be lower due to the LUMO energies below −4.0 eV. The theoretical trends obtained from B3LYP calculations were compared with the results from M06-2X range-separated functional. The charge-transport properties of 5H, 11H-anthra [2,3-c:6,7-c']bis ([1,2,5]thiadiazole)-5,11-dione were also theoretically investigated for the parallel-shifted and linear dimer configurations obtained from the X-ray crystal structure.