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Getting Ready for the Hydrogen Evolution Reaction: The Infrared Spectrum of Hydrated Aluminum Hydride–Hydroxide HAlOH + (H 2 O) n −1 , n= 9–14
Author(s) -
Heller Jakob,
Tang Wai Kit,
Cunningham Ethan M.,
Demissie Ephrem G.,
Linde Christian,
Lam Wing Ka,
Ončák Milan,
Siu ChiKit,
Beyer Martin K.
Publication year - 2021
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202105166
Subject(s) - hydride , hydrogen , hydrogen bond , infrared spectroscopy , infrared , chemistry , molecule , spectroscopy , acceptor , absorption (acoustics) , proton , hydroxide , absorption spectroscopy , aluminium , ion , crystallography , photochemistry , inorganic chemistry , materials science , physics , organic chemistry , optics , composite material , condensed matter physics , quantum mechanics
Hydrated singly charged aluminum ions eliminate molecular hydrogen in a size regime from 11 to 24 water molecules. Here we probe the structure of HAlOH + (H 2 O) n−1 , n=9–14, by infrared multiple photon spectroscopy in the region of 1400–2250 cm −1 . Based on quantum chemical calculations, we assign the features at 1940 cm −1 and 1850 cm −1 to the Al−H stretch in five‐ and six‐coordinate aluminum(III) complexes, respectively. Hydrogen bonding towards the hydride is observed, starting at n=12. The frequency of the Al−H stretch is very sensitive to the structure of the hydrogen bonding network, and the large number of isomers leads to significant broadening and red‐shifting of the absorption of the hydrogen‐bonded Al−H stretch. The hydride can even act as a double hydrogen bond acceptor, shifting the Al−H stretch to frequencies below those of the water bending mode. The onset of hydrogen bonding and disappearance of the free Al−H stretch coincides with the onset of hydrogen evolution.