Integrative Self‐Sorting of Bipyridinium/Diazapyrenium‐Based Ligands into Pseudo[1]rotaxanes

Abstract

We present here the design and synthesis of a series of multicomponent supramolecular architectures, structures formed by the Pd /Pt -directed integrative social self-sorting in aqueous media of pairs of complementary N-monoalkyl-4,4'-bipyridinium/2,7-diazapyrenium-based ligands. Out of the different potential outcomes of the processes, we have found out how the designed systems selectively enhance the production of pseudo[1]rotaxanes, hermaphroditic host-guest aggregates that maximize the strength of the occurring π-π, C-H⋅⋅⋅π, and hydrophobic interactions, as well as the number of those interactions per receptor. It is also demonstrated how both integrative social and narcissistic Pd -directed self-sorting can occur orthogonally and concomitantly for this type of ditopic ligands.

Self‐Assembly of Pseudo[1]rotaxanes by Palladium(II)/Platinum(II)‐Directed Integrative Social Self‐Sorting: Is the Metal Required?

“…Reached this point in our study, we wondered whether the robust π ‐donor/acceptor characteristics of our designed matching pairs L 1 /(±)‐ L 3 and L 5 /(±)‐ L 4 , would be sufficient to promote the observed social self‐sorting even in the absence of the directing force of the metal cations. In the case of L 1 /(±)‐ L 3 , we found that, as previously observed for L 1 / (±)‐ L 2 , [10] the metal centers were imperative for the self‐sorting leading to (±)‐ S 5a,b . Consequently, 1 H‐NMR experiments recorded within the concentration window studied for the self‐assembly of those pseudo[ 1 ]rotaxanes, using equimolar mixtures of the above‐mentioned matching pairs were congruent with nothing but the sum of the individual spectra, accounting for the lack of intermolecular interactions between the complementary ligands on the absence of the Pd(II)/Pt(II) complexes.…”

“…The new amphiphilic ligands (±)‐ L 3–4 were adequately synthesised in an analogous fashion as previously reported for (±)‐ L 2 , [10,14] by using our in‐house methodology for the preparation of functionalized ditopic N ‐monoalkyl‐4,4’‐bipyridinium‐based derivatives (Scheme 2 and Supporting Information for synthetic procedures and characterization) [15] …”

“…[11] On the other hand, intramolecular association can take place leading to self-inclusion complexes, which have demonstrated is applicability as precursors of a variety of interlocked structures, [12] or in the development of indicator displacement assays for analyte sensing. [13] In our specific case (Scheme 1), [10] we found that pseudo[1] rotaxanes (�)-S 1a,b could be efficiently prepared in water by Pd (II)/Pt(II)-directed self-assembly, using the L-shaped ligand L 1 and its matching amphiphilic counterpart (�)-L 2 , which owns an electron-rich dioxophenylene subunit attached though a flexible polyethylene glycol-based linker to the common πdeficient N-monoalkyl-4,4'-bipyridinium moiety found in both ligands. Remarkably, (�)-S 1a,b were the only products detected on the M 1 /M 2 -directed self-assembly processes, with no observation of the homodimeric species (�)-S 2a,b and (�)-S 3a,b .…”

“…In our specific case (Scheme 1), [10] we found that pseudo[ 1 ]rotaxanes (±)‐ S 1a,b could be efficiently prepared in water by Pd(II)/Pt(II)‐directed self‐assembly, using the L‐shaped ligand L 1 and its matching amphiphilic counterpart (±)‐ L 2 , which owns an electron‐rich dioxophenylene subunit attached though a flexible polyethylene glycol‐based linker to the common π ‐deficient N ‐monoalkyl‐4,4‘‐bipyridinium moiety found in both ligands. Remarkably, (±)‐ S 1a,b were the only products detected on the M 1 / M 2 ‐directed self‐assembly processes, with no observation of the homodimeric species (±)‐ S 2a,b and (±)‐ S 3a,b .…”

“…Following these ideas and our interest on the self‐assembly of dynamic host‐guest systems, [8,9] we have recently described the multicomponent supramolecular synthesis in aqueous media of a series of heterodimeric pseudo[ 1 ]rotaxanes [10] . This type of host‐guest complexes is of high current interest for a series of reasons.…”