Formation of Al ₁₃ I ^- : Evidence for the Superhalogen Character of Al ₁₃

Abstract

Al13- is a cluster known for the pronounced stability that arises from coincident closures of its geometric and electronic shells. We present experimental evidence for a very stable cluster corresponding to Al13I-. Ab initio calculations show that the cluster features a structurally unperturbed Al13- core and a region of high charge density on the aluminum vertex opposite from the iodine atom. This ionically bound magic cluster can be understood by considering that Al13 has an electronic structure reminiscent of a halogen atom. Comparisons to polyhalides provide a sound explanation for our chemical observations.

Effects of solvation shells and cluster size on the reaction of aluminum clusters with water

“…The three Al-H bonds in the final Al 17 system include two from the detached Al atom. Thus the final Al 17 superatom has only one Al-H bond corresponding to a surface H atom, which is the same number as in the Al 16 and Al 18 systems.…”

“…In contrast, no H 2 molecule is produced in the pure water system. The production of a larger number of H 2 molecules in the Al 18 system is attributed to the increasing number of Al-(OH)-Al bridging bonds, which will be discussed later in this paper. We do not observe any stable bridging bonds in Al 16 and Al 17 systems.…”

“…Here, size-selectivity is studied by comparing highly reactive Al 17 with less reactive Al 16 and Al 18 , as observed in gas-phase reaction. 20,21 The observed fast reaction rates and calculated low reaction energy barriers are explained by the same reaction mechanisms as in our previous study.…”

“…A remarkable example is an Al superatom, i.e., a cluster consisting of a magic number of Al atoms. 18,19 Hydrogen molecules were produced through gas-phase reaction of Al superatoms with water molecules, where Al 12 and Al 17 showed particularly higher reactivity compared with other cluster sizes. 20,21 The size selectivity of superatoms for gas-phase reaction with water molecules has been explained through geometric factors.…”

Closed-Cage Tungsten Oxide Clusters in the Gas Phase

“…3 Magic number clusters showing enhanced stability have been reported for Si 13 4 and Al 13 . 5 Whereas mass selected positively charged Si 13 clusters were completely unreactive to both ethylene and NO, Si clusters with other nuclearities react. The Al 13 cluster does not show any reactivity with oxygen, while other neighboring clusters did.…”