Heller Jakob, Tang Wai Kit, Cunningham Ethan M, Demissie Ephrem G, van der Linde Christian, Lam Wing Ka, Ončák Milan, Siu Chi-Kit, Beyer Martin K
Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstrasse 25, 6020, Innsbruck, Austria.
Department of Chemistry, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon Tong, Hong Kong SAR, P.R. China.
Angew Chem Int Ed Engl. 2021 Jul 26;60(31):16858-16863. doi: 10.1002/anie.202105166. Epub 2021 Jun 4.
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 O) , n=9-14, by infrared multiple photon spectroscopy in the region of 1400-2250 cm . Based on quantum chemical calculations, we assign the features at 1940 cm and 1850 cm 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.
水合单电荷铝离子在由11至24个水分子组成的尺寸范围内消除分子氢。在此，我们通过红外多光子光谱法在1400 - 2250 cm区域探测HAlOH (H₂O)ₙ（n = 9 - 14）的结构。基于量子化学计算，我们将1940 cm和1850 cm处的特征分别归属于五配位和六配位铝(III)配合物中的Al - H伸缩振动。从n = 12开始观察到朝向氢化物的氢键作用。Al - H伸缩振动的频率对氢键网络的结构非常敏感，大量的异构体导致氢键合Al - H伸缩振动吸收的显著展宽和红移。氢化物甚至可以作为双氢键受体，将Al - H伸缩振动频率移至低于水弯曲模式的频率。氢键作用的开始和游离Al - H伸缩振动的消失与析氢的开始相吻合。
