Molecules with non-bonding states: Juan Casado's lecture at Beilstein Symposium

Last week we participated at Beilstein Symposium on p-Conjugated Molecular and Materials, in Germany. Under the title 'Non-bonding states: from radicals to diradicals' our director, Juan Casado, explained to a group of scientists from all over the world our study about the main observable physical and chemical properties of polyclinic aromatic molecules and how they are dictated by the states and molecular orbitals around the gap.

In his lecture, he explained that the midgap positions are dominated by states with non-bonding character which separates the chirally symmetric bonding and anti-bonding orbitals. The frontier orbitals of pi-conjugated molecules , aside of their aromatic or anti-aromatic characters, aside of the shapes and aside of the number of pi-electrons in delocalization, are characterized by fractions of non-bonding orbitals. The existence of such non-bonding orbitals is usually paralleled by their disjoint character which makes them ideally suited to minimize electron correlation / repulsion energy. With this non-bonding orbitals, it is also possible to construct the bonding and anti-bonding orbitals from which the hybridization energy emerges.

The Huckel molecular orbital theory (more familiar to chemists) or the tight-binding model (more familiar to physicists) provide the ideal framework to approach the electronic, optical and magnetic properties of many polyclinic organic molecules in an easy way. In this contribution all this aspects of the impact of the energies in the formation of open-shell molecules and the relevance and role of the non-bonding states is discussed.

Diradicaloid molecules represent cornerstone systems to explore the nature of the chemical bond and the validity of its theories. Recently, they have also gained relevance as multipurpose substrates for organic electronic applications. The formation of diradicaloid molecules from their non-bonding orbitals was the object of the discussion.

We want to thank the organization of this symposium to let us participate and also congratulate them for how interesting it was to learn about other colleagues and have the opportunity of discuss our studies.