Excited state aromatization assisted push-pull abilities of two unsaturated oxazolone derivatives

Abstract EN

Molecular structures of two unsaturated oxazolone derivatives involving furan rings, which are decorated with p-tolyl (FurM) and 4-nitro phenyl (FurN), were investigated by X-ray crystallography and quantum chemical calculations.

Their ground and excited states were examined by DFT and TD-DFT computations with the aid of topological electron density studies, NBO and Charge Decomposition Analysis.

Both compounds have push-pull (D–p–A) framework using oxazolone ring as p-linker.

Depending on the transitions from the ground to excited states, intramolecular charge transfer (ICT) in both compounds results in aromatization of oxazolones.

Push-pull ability of FurN has more pronounced than that of FurM.

The use of furan instead of almost fully aromatic benzenoid ring reduces HOMO_LUMO band gap due to relatively low aromaticity level of furan.

Introduction of nitro substituent leads to a further reduction in HOMO_LUMO gap.

In addition, electronic redistribution in the excited state results in aromatization of oxazolone moieties without elongation of carbonyl bonds.