Electronic characterization of all-thiophene conducting dendrimers: Molecules and assemblies

The molecular and electronic structure of all-thiophene dendrimers in both the neutral and oxidized states have been investigated performing quantum mechanical calculations on systems of up to 30 rings. Results evidenced that the repulsive steric interactions between the neighboring thiophene rings induce significant distortions from the planarity independently of the electronic state. On the other hand, the ionization potential per thiophene ring and the lowest π-π∗ transition energy decreases with the inverse of the longest α-conjugated chain of the dendrimer, i.e. when the generation increases. The lowest π-π∗ transition energy predicted for an infinite generation dendrimer is 2.08 eV indicating that these materials are potential candidates to be used in optoelectronics. Additionally, Quantum mechanics/molecular mechanics calculations have been performed considering both the sandwich and T-shaped supramolecular arrangements. Results showed not only the stability of these aggregates but also the significant influence of the intermolecular electronic delocalization in the electronic properties of these materials.