Description
Expanded porphyrins are currently recognized as the ideal test bed to explore the correlation between molecular properties and (anti)aromaticity.[1] Besides Hückel and Möbius aromaticity, these macrocycles provide the elusive “yin yang pair” to verify experimentally the reversal of aromaticity in the lowest triplet state, known as Baird’s rule. At present, various photophysical properties, such as absorption spectra features, excited-state lifetime and two-photon absorption, are widely used to assess experimentally whether expanded porphyrins are aromatic, antiaromatic, or nonaromatic. However, the quantification of the aromaticity in such large macrocycles is very challenging. In this talk, I will first introduce a multidimensional approach to quantify Hückel and Möbius aromaticity, based on global and local descriptors rooted on the energetic, magnetic, reactivity, structural and electronic criteria.[2] Then, I will focus on the complex structure-property relationships between aromaticity, π-conjugation topology and photophysical properties.[3] Importantly, we found that the absorption spectra of certain antiaromatic Hückel structures are characterized by more intense absorption bands than its aromatic homologues, contrary to the general statement that antiaromatic porphyrinoids exhibit significantly attenuated absorption bands as compared to aromatic ones. Similarly, our results pinpoint the importance of symmetry and topology on the first and second hyperpolarizability, while aromaticity has a not clear influence on these quantities. Overall, I will show how the concept of the reversal of aromaticity upon topology interconversions can be exploited to create efficient nonlinear optical switches.[4]| Period | 31 Jul 2019 |
|---|---|
| Event title | International conference on excited state aromaticity and antiaromaticity |
| Event type | Conference |
| Location | Sitguna, SwedenShow on map |
| Degree of Recognition | International |