It can be explained as a consequence of the local perturbations that are related to the N-H•••O hydrogen bond: Because the oxygen atom participates in the hydrogen bond, electron density is withdrawn from the Al atom, leading to an increased positive polarisation which favours the formation of an Al-F bond. Additionally, the oxygen atom is somewhat displaced into the ast cage, rendering the Al atom more amenable to an expansion of its coordination environment to trigonal-bipyramidal. The preferred direction of fluoride displacement resembles the ordering of the pyritohedron-like d4r cages observed in GeO2-AST_QNU: In both cases, the reduced symmetry of the OSDA, together with its ability to form hydrogen bonds, causes an energetic preference for a particular orientation of the fluoride-containing d4r cages. of which was attributed to "terminal" fluoride anions. Tentatively, this signal could be due to fluoride anions that remain bonded to a single Al atom for relatively extended periods (on the timescale of NMR experiments). The fact that the DFT optimisations did not deliver Al-F bonds indicates that the structures with fluoride at the cage centre correspond to local minima on the potential energy surface, which the DFT optimisation algorithm cannot leave.