Plenates: Anion‐Dependent Self‐Assembly of the Pyrrole Cage Encapsulating Silver(I) Clusters

Abstract

The self-assembly of 2,5-diformylpyrrole, tris(2aminoethyl)amine, and silver(I) yielded, depending on the size and basicity of the anion, new cascade complexes or plenates, that is, cryptates incorporating Ag n n + clusters. The nature of the product was counterion-dependent, and its formation was either driven by cascade anion binding or by argentophilic interactions stabilizing the cluster within the cavity. The reaction of plenates with tetrabutylammonium halides resulted in the protonation-coupled replacement of the Ag 3 3 + with anion(s), yielding cascade cryptates.

Argentophilic Interactions, Flexibility, and Dynamics of Pyrrole Cages Encapsulating Silver(I) Clusters

“…For this system, we also performed studies at the DFT level of theory, locating a stationary point of Ag + outside of 1 that interacts with two pyrrole moieties (18.6 kcal/mol with respect to the [Ag 4 -B ⊂ 1] + ), followed by a transition state of Ag + entering 1 (23.2 kcal/mol), a stationary point with the Ag + ion inside 1 but not in optimal position (14.4 kcal/mol), and finally the fully optimized structure of [Ag 4 -B ⊂ 1] + (0.0 kcal/mol); see Figure B. These results agree with the experimental data, suggesting a relatively easy formation of such complexes and conversion from systems with fewer Ag + ions to systems with more Ag + ions as soon as additional silver(I) is introduced . In all other cases, the barriers are of similar height, apart from when the Ag + ion enters the empty cage which has an energy barrier of around 20 kcal/mol.…”

“…Interestingly, in the case of Ag 4 4+ and Ag 5 5+ clusters, such reduced models of cage 1 lead to entirely different geometries for the silver clusters (see the Supporting Information). This structural variability resembles the stochastic dynamic behavior for the formation of higher-order Ag n n+ clusters observed during the experimental investigations, which is analyzed at the end of this study.…”

“…In all calculations, the starting structures were based on the available crystal structures of pyrrole cages encapsulating selected ions . Most calculations were performed using a two-step approach.…”

“…28 This unique mode of reactivity was illustrated by Nelson, who described the transformation of the disilver cage into the trisilver cryptate, enabling both modification of metal coordination sites within the cage and also reconfiguration of the capsule conformation. 28 Recently, we reported on the iminopyrrole cage, 29 which, depending on the silver(I) source, formed cascade cryptates embedding fluoride or chloride between two metal centers, or else formed plenates, i.e., cryptates incorporating silver(I) clusters accommodated within the cavity (Scheme 1). 29 Quantum chemical computational methodologies serve as predictive approaches to determine cage structure, topology, cavity size, and associated molecular properties within extensive data sets of porous organic cages.…”

“…28 Recently, we reported on the iminopyrrole cage, 29 which, depending on the silver(I) source, formed cascade cryptates embedding fluoride or chloride between two metal centers, or else formed plenates, i.e., cryptates incorporating silver(I) clusters accommodated within the cavity (Scheme 1). 29 Quantum chemical computational methodologies serve as predictive approaches to determine cage structure, topology, cavity size, and associated molecular properties within extensive data sets of porous organic cages. 30 This enables the guidance of synthetic researchers toward the identification and development of materials possessing targeted properties.…”