Energy‐Landscape‐Independent Kinetic Trap of an Incomplete Cage in the Self‐Assembly of a Pd₂L₄ Cage

Abstract

A kinetic trap is the metastable species that is transiently or constantly produced during the reaction by trapping in a deep energy well. In most cases, the reactivity of kinetically trapped species is relatively low under the reaction conditions. Herein, we report another type of kinetically trapped species that is an incomplete cage (IC) intermediate produced during the self-assembly of a Pd L cage from ditopic ligand (L) and Pd ions with a certain lifetime, although IC has a high enough reactivity to be converted into the cage with the reaction of free L, which was confirmed by the reaction of the isolated IC and L under the self-assembly conditions. IC was kinetically trapped not because IC lies on the bottom of a deep energy well but because the conversion of the intermediates essential for the conversion of IC to the cage preferentially takes place; IC was kinetically trapped independently of the shape of the energy landscape of the self-assembly.

Inducing Social Self‐Sorting in Organic Cages To Tune The Shape of The Internal Cavity

“…We previously used density functional theory (DFT) formation energies to explain the thermodynamically preferred cage topologies in the dynamic imine-based selfassembly processes. [41,[57][58][59] Comparing the thermodynamic stabilities of potential cage products can be ag ood guide to selectivity,b ut the reaction outcome can also be affected by factors,s uch as reaction kinetics, [39,[60][61][62][63][64] solvent effects, [65][66][67][68] and the solubilities of the species involved in the equilibrium. [33,40,47] In parallel with the synthetic efforts,w eu sed computational techniques to predict the stability of the different homo-and heteroleptic structures originating from aldehydes B1-B2 and L1-L4.T he experimentally observed outcomes agreed with the relative gas-phase formation energies of the possible Tet 3 Di 6 products,s howing the predictive power of the simple model for the self-sorting behaviour of imine-based organic cages.…”

Self‐Assembly Processes of Pd(II)‐ and Pt(II)‐Linked Discrete Self‐Assemblies Revealed by QASAP

“…Because of lower symmetry of IC than the Pd 2 6 4 cage, the isolation of IC helped clear characterization of IC by various NMR measurements. The almost quantitative conversion of IC to the cage by the reaction of a free ditopic ligand 6 could be monitored by 1 H NMR spectroscopy, which indicates that the first intermolecular reaction between IC and 6 is the rate‐determining step; the intramolecular ligand exchange in Pd 2 6 4 Py* takes place much faster than the first intermolecular ligand exchange . With this success, it is quite reasonable to expect that heterotopic cages can selectively be synthesized by the reaction of IC with other ditopic ligands.…”

“…Multiple self‐assembly pathways were also found in the self‐assembly of a Pd 2 6 4 cage from U‐shaped ditopic ligand 6 and PdPy* 4 (BF 4 ) 2 (Figure ) . In the first stage of the self‐assembly (within 5 min), besides the cage, a Pd 2 6 3 Py* 2 incomplete cage ( IC ) and 1 H‐NMR‐unobservable intermediates ( Int(I) ) whose average composition is expressed as were produced (stage I).…”

“…Therefore, the reason why IC was kinetically trapped during the self‐assembly of the cage is not because IC is stabilized by being trapped in a deep energy well on an energy landscape, but because of the faster intramolecular conversion of Int(I) into the cage than the reaction of IC and Int(I) . This makes IC an energy‐landscape‐independent kinetically trapped species …”

Inducing Social Self-Sorting in Organic Cages to Tune the Shape of the Internal Cavity

“…We previously used density functional theory (DFT) formation energies to explain the thermodynamically preferred cage topologies in the dynamic imine-based self-assembly processes. [39,[55][56][57] Comparing the thermodynamic stabilities of potential cage products can be a good guide to selectivity, but the reaction outcome can also be affected by factors such as reaction kinetics, [37,[58][59][60][61][62] solvent effects, [63][64][65][66] and the solubilities of the species involved in the equilibrium. [31,38,45] In parallel with the synthetic efforts, we used computational techniques to predict the stability of the different homo-and heteroleptic structures originating from aldehydes B1-2 and L1-4.…”