Embedding a guest gold cluster in an organic host. Evaluation of the encapsulation nature in a Au₁₈–superphane host–guest aggregate

Formation of supramolecular aggregates incorporating Au₁₈ into a suitable bioinspired polyfunctional superphane cavity provides novel functionality to the overall structure. We evaluated the favorable incorporation of the Au₁₈ cluster into the superphane cavity. This amounted to -145.3 kcal mol^-1, provided mainly by electrostatic-type interactions (54.9%). Charge transfer characteristics involving host ← guest and host → guest backdonation through S ← Au and S → Au contacts led to overall Au₁₈ → 1 superphane charge transfer. Charge transfer consisted of a charge hopping rate (<i>k</i>_CT) in the range of ultrafast electron transfer, calculated to be 2.2 × 10¹³ s^-1 at 300 K. Thus, Au₁₈ → 1 charge transfer was driven by coordinating and short contacts towards the superphane available cavity, resulting in a supramolecular structure of the donor-acceptor (D-A) system. We expect that the current approach can be useful for further rationalizing the relevant stabilizing factors to ensure the stable aggregation of metallic clusters in organic host cavities during the making of novel functional cluster-based host-guest aggregates.