Theoretical study of the fragmentation of ionized benzophenone

A detailed theoretical study of the various possible fragmentation reactions of the benzophenone radical cation was carried out for the first time. In the first step, we optimized the geometries of all the structures resulting from the fragmentation of this cation using density functional theory (DFT). Our calculations were performed in the gas phase using the aug-cc-pVTZ basis set and the PBE1PBE functional. We determined the optimized structural parameters and the harmonic and anharmonic frequencies. The energies corresponding to all the optimized molecules were recalculated using the coupled cluster method CCSD(T). Upon comparing the fragmentation reaction energies, we found that the principal reaction was that leading to C₇H₅O⁺ and ·C₆H₅. We were able to theoretically demonstrate the existence of different fragments of the benzophenone cation: CO, CO⁺·, ·C₆H₅, C₆H₅⁺, ·C₇H₅O, C₇H₅O⁺, biphenyl, and (biphenyl)⁺·, and we found that the main products of the fragmentation reactions of the benzophenone cation are C₇H₅O⁺ and (biphenyl)⁺·, which have been observed experimentally using slow photoelectron spectroscopy (SPES). Our theoretical results are in good agreement with the experimental results from benzophenone cation spectroscopy and fragmentation obtained using Benoît Soep's equipment at Synchrotron SOLEIL.