Structures and Energetics of Bicyclic Organic Molecules Using Photoelectron Spectroscopy

Abstract

Organic molecules are important in chemistry and relevant to many applications. The bicyclic molecules of anthranil, 1,2-benzisoxazole, and benzoxazole are all made from a benzene ring and a five-membered ring containing a nitrogen and oxygen atoms. They are often used as scaffolds in medicinal chemistry and drug design. However, despite their notable use in synthesis, not much is known about the energetics of these molecules. Using photoelectron spectroscopy, the adiabatic electron affinities of anthranilyl and 1,2-benzisoxazolyl were measured. Anthranilyl has two distinct states, nearly overlapping electronic adiabatic electronic affinities of 3.12 eV and 3.34 eV, while for 1,2-benzisoxazolyl only one state is observed around 2.94 eV. The completion of these experiments allows for a broader comparison to be made between the isomer family and the five-membered rings. Combined with previous work done for the other three molecules, the effect that location of the heteroatoms has on the energies and electronic structures of the radical states can be analyzed. The results indicate that anthranilyl has the largest EA of the bicyclic isomers and the addition of the benzene ring causes additional ?-stabilization. The similarities in the behaviors between the bicyclic rings and the five-membered rings show that the addition of the benzene does not always have a large effect. This work brings light to the relationship between molecules in an isomer family and the effect that moving the heteroatoms can have.