%0 Journal Article %1 kaiser2018orthobenzyne %A Kaiser, D. %A Reusch, E. %A Hemberger, P. %A Bodi, A. %A Welz, E. %A Engels, B. %A Fischer, I. %D 2018 %J Phys. Chem. Chem. Phys. %K Engels myown %N 6 %P 3988-3996 %R 10.1039/C7CP08055G %T The ortho-benzyne cation is not planar %U https://doi.org/10.1039/C7CP08055G %V 20 %X A recent review on the photoionisation of the C6H4 isomer ortho-benzyne suggests that bands reported in earlier photoelectron spectra might be due to side products or contaminations, while computations raise doubts, whether the cation has a planar geometry. We therefore reinvestigate the photoionisation of ortho-benzyne, generated by pyrolysis from benzocyclobutenedione, by photoion mass-selected threshold photoelectron (ms-TPE) spectroscopy using synchrotron radiation. The experiments are accompanied by a theoretical study that investigates the structure of the ortho-benzyne cation systematically as a function of the computational method, up to CASPT2(11,14) ab initio computations. Our study leads to a re-evaluation of the ionisation energy of ortho-benzyne. It reveals that the ortho-benzyne cation has indeed a twisted C2 geometry rather than a C2v structure. A vertical ionisation energy IEvert of 9.77 eV and an adiabatic ionisation energy of IEad = 9.56 eV are computed for ortho-benzyne. A Franck–Condon simulation of the photoelectron spectrum based on the CASPT2 results and including three electronic states of the cation is in agreement with the experiment and yields IEad = 9.51 eV (+50 meV/−100 meV). Since this value is in contrast with previous work, the ionisation energy has to be revised based on our study. Computational methods based on density functional theory give a reasonable description of the cationic ground state, but fail for the corresponding excited electronic states that are indispensible for a proper assignment of the photoelectron spectrum.

@article{kaiser2018orthobenzyne, abstract = {A recent review on the photoionisation of the C6H4 isomer ortho-benzyne suggests that bands reported in earlier photoelectron spectra might be due to side products or contaminations{,} while computations raise doubts{,} whether the cation has a planar geometry. We therefore reinvestigate the photoionisation of ortho-benzyne{,} generated by pyrolysis from benzocyclobutenedione{,} by photoion mass-selected threshold photoelectron (ms-TPE) spectroscopy using synchrotron radiation. The experiments are accompanied by a theoretical study that investigates the structure of the ortho-benzyne cation systematically as a function of the computational method{,} up to CASPT2(11{,}14) ab initio computations. Our study leads to a re-evaluation of the ionisation energy of ortho-benzyne. It reveals that the ortho-benzyne cation has indeed a twisted C2 geometry rather than a C2v structure. A vertical ionisation energy IEvert of 9.77 eV and an adiabatic ionisation energy of IEad = 9.56 eV are computed for ortho-benzyne. A Franck–Condon simulation of the photoelectron spectrum based on the CASPT2 results and including three electronic states of the cation is in agreement with the experiment and yields IEad = 9.51 eV (+50 meV/−100 meV). Since this value is in contrast with previous work{,} the ionisation energy has to be revised based on our study. Computational methods based on density functional theory give a reasonable description of the cationic ground state{,} but fail for the corresponding excited electronic states that are indispensible for a proper assignment of the photoelectron spectrum.}, added-at = {2019-03-07T20:31:10.000+0100}, author = {Kaiser, D. and Reusch, E. and Hemberger, P. and Bodi, A. and Welz, E. and Engels, B. and Fischer, I.}, biburl = {https://www.bibsonomy.org/bibtex/239b7077031f8cb7bc816f8bec37e40eb/akengels}, description = {The ortho-benzyne cation is not planar - Physical Chemistry Chemical Physics (RSC Publishing)}, doi = {10.1039/C7CP08055G}, interhash = {c7800ab293a9dbe14c17cff23fa56105}, intrahash = {39b7077031f8cb7bc816f8bec37e40eb}, journal = {Phys. Chem. Chem. Phys.}, keywords = {Engels myown}, number = 6, pages = {3988-3996}, timestamp = {2020-06-21T07:16:37.000+0200}, title = {The ortho-benzyne cation is not planar}, url = {https://doi.org/10.1039/C7CP08055G}, volume = 20, year = 2018 }