Opto-electronic properties of isomers of azobispyridine

The density-functional theoretical studies are carried out to examine the isomerization and opto-electronic properties of heteroaryl azobispyridine derivatives (AzoPy). Among the isomers, trans o-o-AzoPy is the lowest in energy. Gibbs free energy change associated with the trans-cis isomerization of AzoPy via rotation is found to be 34-38 kcal/mol, whereas the reverse transformation occurs with a relatively low barrier (21-24 kcal/mol). The dipole moment and length of the molecule are significantly changed due to isomerization suggesting their use in molecular machines. In dimer, trans o-o-AzoPy adopts a parallel-slipped orientation. The charge carrier mobilities indicate the molecules as electron transporters.