Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment
Gas phase photodissociation electronic spectra of protonated azobenzene (ABH+) and 4-(dimethylamino)azobenzene (dmaABH+) were measured in a cryogenically cooled ion trap at temperatures of a few tens of Kelvin. Experimental results were complemented with electronic structure calculations in the grou...
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paper:paper_10895639_v120_n22_p3897_Feraud2023-06-08T16:06:35Z Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment Marceca, Ernesto Jose Absorption spectroscopy Azobenzene Charge transfer Chemical reactions Dihedral angle Electronic structure Ground state Isomers Photodissociation Protonation Ultraviolet spectroscopy Electronic spectrum Electronic structure calculations Low-lying excited state Molecular ions Neutral molecules Protonation site UV-vis spectra Vibrational progressions Excited states Gas phase photodissociation electronic spectra of protonated azobenzene (ABH+) and 4-(dimethylamino)azobenzene (dmaABH+) were measured in a cryogenically cooled ion trap at temperatures of a few tens of Kelvin. Experimental results were complemented with electronic structure calculations in the ground state at the MP2/cc-pVDZ level of theory, and in the low lying excited states using the RI-CC2 method. Calculated energies revealed that only the trans isomers of the azonium molecular ions (protonation site on the azo group) will likely exist in the trap at the temperatures achieved in the experiment. The first transition of trans-ABH+ is π∗ ← π, and the absorption band in the spectrum appears strongly red-shifted from that of the neutral molecule. The calculations showed that upon excitation the quasi-planar ground state (S0) transforms into a chairlike excited state (S1) by twisting the CNNC dihedral angle about 96°. A 41 cm-1 active vibrational progression found in the ABH+ spectrum may be associated with the twisting of the azo bond. Conversely, the electronic spectrum of dmaABH+ exhibits a steep and unstructured S1 ← S0 absorption corresponding to a less distorted S1 state. The next two quasi-degenerate bands in the ABH+ spectrum evidence sharper onsets and a charge transfer character. Using a second fragmentation laser and an additional He cooling pulse in the trap, it was possible to measure the UV spectrum of cold benzenediazonium fragments. © 2016 American Chemical Society. Fil:Marceca, E. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2016 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10895639_v120_n22_p3897_Feraud http://hdl.handle.net/20.500.12110/paper_10895639_v120_n22_p3897_Feraud |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
Absorption spectroscopy Azobenzene Charge transfer Chemical reactions Dihedral angle Electronic structure Ground state Isomers Photodissociation Protonation Ultraviolet spectroscopy Electronic spectrum Electronic structure calculations Low-lying excited state Molecular ions Neutral molecules Protonation site UV-vis spectra Vibrational progressions Excited states |
| spellingShingle |
Absorption spectroscopy Azobenzene Charge transfer Chemical reactions Dihedral angle Electronic structure Ground state Isomers Photodissociation Protonation Ultraviolet spectroscopy Electronic spectrum Electronic structure calculations Low-lying excited state Molecular ions Neutral molecules Protonation site UV-vis spectra Vibrational progressions Excited states Marceca, Ernesto Jose Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment |
| topic_facet |
Absorption spectroscopy Azobenzene Charge transfer Chemical reactions Dihedral angle Electronic structure Ground state Isomers Photodissociation Protonation Ultraviolet spectroscopy Electronic spectrum Electronic structure calculations Low-lying excited state Molecular ions Neutral molecules Protonation site UV-vis spectra Vibrational progressions Excited states |
| description |
Gas phase photodissociation electronic spectra of protonated azobenzene (ABH+) and 4-(dimethylamino)azobenzene (dmaABH+) were measured in a cryogenically cooled ion trap at temperatures of a few tens of Kelvin. Experimental results were complemented with electronic structure calculations in the ground state at the MP2/cc-pVDZ level of theory, and in the low lying excited states using the RI-CC2 method. Calculated energies revealed that only the trans isomers of the azonium molecular ions (protonation site on the azo group) will likely exist in the trap at the temperatures achieved in the experiment. The first transition of trans-ABH+ is π∗ ← π, and the absorption band in the spectrum appears strongly red-shifted from that of the neutral molecule. The calculations showed that upon excitation the quasi-planar ground state (S0) transforms into a chairlike excited state (S1) by twisting the CNNC dihedral angle about 96°. A 41 cm-1 active vibrational progression found in the ABH+ spectrum may be associated with the twisting of the azo bond. Conversely, the electronic spectrum of dmaABH+ exhibits a steep and unstructured S1 ← S0 absorption corresponding to a less distorted S1 state. The next two quasi-degenerate bands in the ABH+ spectrum evidence sharper onsets and a charge transfer character. Using a second fragmentation laser and an additional He cooling pulse in the trap, it was possible to measure the UV spectrum of cold benzenediazonium fragments. © 2016 American Chemical Society. |
| author |
Marceca, Ernesto Jose |
| author_facet |
Marceca, Ernesto Jose |
| author_sort |
Marceca, Ernesto Jose |
| title |
Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment |
| title_short |
Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment |
| title_full |
Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment |
| title_fullStr |
Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment |
| title_full_unstemmed |
Photodissociation UV-Vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment |
| title_sort |
photodissociation uv-vis spectra of cold protonated azobenzene and 4-(dimethylamino)azobenzene and their benzenediazonium cation fragment |
| publishDate |
2016 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_10895639_v120_n22_p3897_Feraud http://hdl.handle.net/20.500.12110/paper_10895639_v120_n22_p3897_Feraud |
| work_keys_str_mv |
AT marcecaernestojose photodissociationuvvisspectraofcoldprotonatedazobenzeneand4dimethylaminoazobenzeneandtheirbenzenediazoniumcationfragment |
| _version_ |
1768544238997340160 |