Solvent‐controlled separation of integratively self‐sorted Pd2LA2LB2 coordination cages

Abstract

The integrative implementation of multiple different components into metallosupramolecular self-assemblies requires sophisticated strategies to avoid the formation of statistical mixtures. Previously, the key focus was set on thermodynamically driven reactions of simple homoleptic into complex heteroleptic structures. Using Pd2LA2LB2-type coordination cages, we herein show that integrative self-sorting can be reversed by a change of solvent (from DMSO to MeCN) to favor narcissistic re-segregation into coexisting homoleptic species Pd2LA4 and Pd3LB6. Full separation (“unsorting”) back to a mixture of the homoleptic precursors was finally achieved by selective precipitation of Pd3LB6 with anionic guest G1 from MeCN, keeping pure Pd2LA4 in solution. When a mixture of homoleptic Pd3LB6 and heteroleptic Pd2LA2LB2 is exposed to a combination of two different di-anions (G1 and G2) in DMSO, selective guest uptake gives rise to two defined coexisting host–guest complexes. A joint experimental and deep theoretical investigation via liquid-state integral equation theory of the reaction thermodynamics on a molecular level accompanied by solvent distribution analysis hints at solvent expulsion from Pd2LA4 to favor the formation of Pd2LA2LB2 in DMSO as the key entropic factor for determining the solvent-specific modulation of the cage conversion equilibrium.