Excited State Aromaticity

Aromaticity is a property normally connected with the ground state of stable molecules. However, not only the ground state of certain species, but also the excited states of some molecules may be aromatic. The aromaticity of excited states has been much less explored than that of the ground state. Although the application of the aromaticity concept to explain the properties and reactivity of excited states is still scarce, there are already many examples in which the concept aromaticity is essential to understand the chemistry of excited states. In this chapter, we comment a number of theoretical and experimental studies of excited state aromaticity and we briefly discuss some examples on the influence of aromaticity in excited state properties and reactions.