Aluminum oxo-fluoride clusters: A first principle investigation of stability, synthetic considerations, and the interaction with water.

Abstract

The introduction of the so called fluorolytic sol-gel synthesis in 2003 gave access to previously inaccessible aluminum oxo-fluorides, thus to nanoscopic materials and, more importantly, novel catalysts. The intermediate cluster structures synthesized and stabilized by Kemnitz and coworkers have mainly been protected by iso-propoxide groups. However, since catalytic reactions take place in a large variety of media, hydrophilic analogs of those clusters would be of interest. In this manuscript, we present a computational analysis for the fluorination reaction, which represents the second part of fluorolytic sol-gel synthesis, and a theoretical study of the synthesized Al4 F4 (μ4 -O)(μ-Oi Pr)5 [H(Oi Pr)2 ] nanostructure's conversion to its hydroxylated analog Al4 F4 (μ4 -O)(μ-OH)5 [H(OH)2 ] utilizing the nudged elastic band method. Furthermore, the role of the fluorine atoms of the cluster in an aqueous medium is evaluated by studying the incremental addition of water molecules to the cluster with and without fluorine atoms. In addition, NMR shifts of clusters exhibiting different substituents are compared. It has been found that the inclusion of an explicit solvent is necessary to capture the magnetic response of the individual cluster atoms in an aqueous solvent correctly. © 2018 Wiley Periodicals, Inc.