ECAMP 15

In our laboratory, we have started a systematic investigation of the reactions involving oxygen atoms and aromatic compounds under single collision conditions using the crossed molecular beam technique with mass spectrometric detection. The first systems we have looked at are O(³P) + benzene [1], pyridine [2], and toluene [3]. More recent results are on O(³P) + ethylbenzene and O(³P) + thiophene, while we plan to investigate the reactions with styrene, anisole, and other functionalized aromatics.

A detailed understanding of these reactive systems has practical implications ranging from biomass gasification to the design of novel space-technology aromatic polymers resistant to the attack by the oxygen atoms in the Low Earth Orbit, where most satellites reside. From a fundamental point of view, these studies aim to derive the structure dependency of the reactivity of aromatics.

As in the case of the O(³P) reactions with unsaturated organic compounds, the investigated reactions are strongly affected by intersystem crossing (ISC) to the underlying singlet potential energy surface with a significant alteration of the reaction mechanism and product branching fractions. ISC can occur in the entrance channel, as observed for the O + pyridine reaction [2], or at a later stage. In all cases, upon ISC, either ring-contraction or ring-opening (in the case of O + thiophene) mechanisms with CO-elimination were observed to be significant or dominant (in the case of the reaction with pyridine and thiophene). The experimental results are interpreted with the help of ad hoc theoretical simulations.

[1] G. Vanuzzo et al., J. Phys. Chem. A 125, 8434 (2021)
[2] P. Recio et al., Nature Chemistry 14, 1405 (2022)
[3] N. Balucani et al., Faraday Disc. 251, 523 (2024)

We acknowledge financial support under the National Recovery and Resilience Plan (NRRP), Mission 4, Component 2, Investment 1.1, Call for tender No. 104 published on 02.02.2022 by the Italian Ministry of University and Research (MUR), funded by the European Union – NextGenerationEU– Project Title 20227W5CLJ Biomass gasification for hydrogen production (Bio4H2) – CUP J53D23001970006 - Grant Assignment Decree No. 961 adopted on 30.06.2023 by the Italian Ministry of Ministry of University and Research (MUR).