Photochemical Hydrogen Storage with Hexaazatrinaphthylene

When irradiated with violet light, hexaazatrinaphthylene (HATN) extracts a hydrogen atom from an alcohol forming a long‐living hydrogenated species. The apparent kinetic isotope effect for fluorescence decay time in deuterated methanol (1.56) indicates that the lowest singlet excited state of the mo...

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Bibliographic Details
Published in:Chemphyschem 2022-06, Vol.23 (11), p.e202200077-n/a
Main Authors: Morawski, Olaf, Gawryś, Paweł, Sadło, Jarosław, Sobolewski, Andrzej L.
Format: Article
Language:English
Subjects:
Absorption spectra
alcohol oxidation
Deuteration
Electron paramagnetic resonance
Ethanol
Excitation
Hydrogen
Hydrogen atoms
hydrogen attachment
Hydrogen storage
Hydrogenation
Isotope effect
Mass spectrometry
Methanol
NMR
Nuclear magnetic resonance
Oxidation
photochemical hydrogen abstraction
proton coupled electron transfer
water oxidation
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Summary:When irradiated with violet light, hexaazatrinaphthylene (HATN) extracts a hydrogen atom from an alcohol forming a long‐living hydrogenated species. The apparent kinetic isotope effect for fluorescence decay time in deuterated methanol (1.56) indicates that the lowest singlet excited state of the molecule is a precursor for intermolecular hydrogen transfer. The photochemical hydrogenation occurs in several alcohols (methanol, ethanol, isopropanol) but not in water. Hydrogenated HATN can be detected optically by an absorption band at 1.78 eV as well as with EPR (electron paramagnetic resonance) and NMR techniques. Mass spectrometry of photoproducts reveal di‐hydrogenated HATN structures along with methoxylated and methylated HATN molecules which are generated through the reaction with methoxy radicals (remnants from alcohol splitting). Experimental findings are consistent with the theoretical results which predicted that for the excited state of the HATN‐solvent molecular complex, there exists a barrierless hydrogen transfer from methanol but a small barrier for the similar oxidation of water. Visible‐light‐driven hydrogen evolution is a very desired photochemical reaction. Similarly, materials for hydrogen storage are being intensively sought. Hexaazatrinaphthylene (HATN), the compound with high electron affinity, excited with visible light oxidizes alcohol forming dihydrogenated HATN, a stable and persistent molecular structure amenable for long‐term hydrogen storage. This may potentially offer new way for hydrogen generation and storage.
ISSN:1439-4235
1439-7641
DOI:10.1002/cphc.202200077