Embedding a Guest Gold Cluster in an Organic Host. Evaluation of the Encapsulation Nature in Au18-Superphane Host-Guest Aggregate

Abstract

The formation of supramolecular aggregates incorporating Au18 into a suitable bioinspired polyfunctional superphane cavity provides novel functionality to the overall structure. Here, we evaluate the favorable incorporation of the Au18 cluster into the superphane cavity, amounting to -145.3 kcal/mol, mainly provided by electrostatic type interactions (54.9%), with contribution from the charge transfer characteristics involving both host←guest and host→guest backdonation through S←Au and S→Au contacts, leading to an overall Au18→1 superphane charge transfer. Furthermore, the charge transfer consists of a charge hopping rate (kCT) in the range of ultrafast electron transfer, calculated to be 2.2 x 1013 s-1 at 300 K. Thus, the Au18→1 charge transfer is driven by both coordinating and short contacts towards the superphane available cavity, resulting in a supramolecular structure of donor-acceptor (D-A) system. We expect that the current approach can be useful in further rationalizing the relevant stabilizing factors to ensure a stable aggregation of metallic clusters into organic host cavities in the making of novel functional cluster-based host-guest aggregates.