Discrete multiporphyrin pseudorotaxane assemblies from di- and tetravalent porphyrin building blocks

Abstract

SummaryTwo pairs of divalent and tetravalent porphyrin building blocks carrying the complementary supramolecular crown ether/secondary ammonium ion binding motif have been synthesized and their derived pseudorotaxanes have been studied by a combination of NMR spectroscopy in solution and ESI mass spectrometry in the gas phase. By simple mixing of the components the formation of discrete dimeric and trimeric (metallo)porphyrin complexes predominates, in accordance to binding stoichiometry, while the amount of alternative structures can be neglected. Our results illustrate the power of multivalency to program the multicomponent self-assembly of specific entities into discrete functional nanostructures.

The Delicate Balance of Preorganisation and Adaptability in Multiply Bonded Host–Guest Complexes

“…EM cannotb em easured directly,b ut can be quantified by double mutant cycle analyses (DMC;F igure 1, top). [5,26,[31][32][33][35][36][37] The DMC connects ad ivalent complex a to two monovalent complexes d through two pathways of two consecutive mutations. By comparison of the four complexes a-d derived from the mutations, all secondary allosterice ffects cancel and the chelate cooperativity remains.…”

“…Recently,w edemonstrated [25,26] the crown ether/ammonium bindingm otif [10,11,[27][28][29][30] to be especially suitable for our purpose as the monovalent interaction is ar eliable, well-understood binding motif. [31][32][33] Furthermore, these systems exhibit alimited molecular size suitable for computational analysis by density functional theory. [25,26,31,34] In our previous studies, we investigated [25,26] the cooperativities in two virtually identical divalent complexes with flexible linkers that exhibited significantly different, but very high chelate cooperativities.…”

“…Fundamental studies of this type will provide quantitative design rules to guide the construction of supramolecular assemblies and receptors. Recently, we demonstrated the crown ether/ammonium binding motif to be especially suitable for our purpose as the monovalent interaction is a reliable, well‐understood binding motif . Furthermore, these systems exhibit a limited molecular size suitable for computational analysis by density functional theory .…”

Allosteric and Chelate Cooperativity in Divalent Crown Ether/Ammonium Complexes with Strong Binding Enhancement

“…We use simple divalent crown/ammonium complexesa smodel systems.These binding motifsa re widely used tool kits for the generation of complex, programmed structures in supramolecular chemistry. [23][24][25][26][27][28][29][30] Their advantages for our purposes are 1) easy synthetic accessibility, 2) solubility in ar ange of organic solvents of different polarity, 3) relatively strong binding interactions, 4) al imited molecular size suitable for computational analysis [29,31] by DFT and molecular dynamics simulations, and 5) aw ell-understood monovalent binding motif.…”

Multivalency as a chemical organization and action principle

“…In order to obtain a deeper understanding of multivalent interactions this Thematic Series in the Beilstein Journal of Organic Chemistry puts its focus to unravel new cellular interactions that are highly relevant [ 2 ] and systematically combines theoretical exploration of defined multivalent supramolecular interactions [ 3 ] as well as new supramolecular designer systems [ 4 – 5 ]. The influence of spacer length and flexibility on the binding affinity of ligands [ 6 ] will be examined as well as the mechanical stability of complexes [ 7 ].…”