Expanding the Scope of Metastable Species in Hydrogen Bonding‐Directed Supramolecular Polymerization

Abstract

We reveal unique hydrogen (H-) bonding patterns and exploit them to control the kinetics, pathways and length of supramolecular polymers (SPs). New bisamide-containing monomers were designed to elucidate the role of competing intra-vs. intermolecular Hbonding interactions on the kinetics of supramolecular polymerization (SP). Remarkably, two polymerizationinactive metastable states were discovered. Contrary to previous examples, the commonly assumed intramolecularly H-bonded monomer does not evolve into intermolecularly H-bonded SPs via ring opening, but rather forms a metastable dimer. In this dimer, all H-bonding sites are saturated, either intra-or intermolecularly, hampering elongation. The dimers exhibit an advantageous preorganization, which upon opening of the intramolecular portion of the H-bonding motif facilitates SP in a consecutive process. The retardation of spontaneous self-assembly as a result of two metastable states enables length control in SP by seed-mediated growth.

Stereomutation and chiroptical bias in the kinetically controlled supramolecular polymerization of cyano-luminogens

“…7c,8b,17 In fact, Fernández and coworkers have very recently demonstrated the ability of selfassembling units decorated with these peripheral moieties to generate supramolecular polymers with intermolecular Hbonding interactions in a consecutive manner, the first step being the formation of dimers in which intra-and intermolecular H-bonding interactions between the amide groups are operative. 18 Consequently, we have not used the commonly utilized variable temperature spectroscopic (UV-Vis or CD) techniques to elucidate the supramolecular polymerization mechanism, but we have utilized denaturalization experiments to derive, if possible, the thermodynamic parameters associated to the supramolecular polymerization of the reported cyano-luminogens (vide infra). Chiroptical properties and morphology of the aggregated species of the cyano-luminogens 1 and 2.…”

“…The spectroscopic and morphologic differences found for AggI and AggII species of luminogens 1 and 2 could be justified by considering the above-mentioned ability of the metastable monomeric species M*, in which the intramolecularly Hbonded pseudocycle is able to form intermolecular H-bonding interactions, to generate the corresponding AggI species. 18 These AggI species would be characterized by the intermediate spectra observed in the freshly prepared mixtures (green lines in Figures 3b and 4b). Furthermore, the presence of two pseudocycles per monomeric unit, and the subsequent intermolecular interaction between them, would yield the kinetically controlled AggI species (Figure S17).…”

Luminescence and Length Control in Nonchelated d8‐Metallosupramolecular Polymers through Metal‐Metal Interactions

“…Chemie and C=O stretching bands characteristic for the equilibrium between open and intramolecularly H-bonded monomers (ν NÀ H (free) = 3454 cm À 1 , ν NÀ H (intra) = 3348 cm À 1 , ν C=O (mixed) = 1655 cm À 1 ). [33] 1A displays an NÀ H stretching band at ν NÀ H = 3286 cm À 1 , and a carbonyl stretching band at ν C=O = 1633 cm À 1 (Figure 4b), in accordance with the formation of intermolecular amide-to-amide H-bonds. [34,35] For SP 1B, the carbonyl stretching band is further displaced to lower wavenumbers (ν C=O = 1628 cm À 1 ), indicating marginally stronger H-bonding.…”

Lumineszenz‐ und Längenkontrolle in nicht‐chelatisierten d8‐metallosupramolekularen Polymeren vermittelt durch Metall‐Metall‐Wechselwirkungen

“…ν NÀ H (intra) � 3350 cm À 1 ). [33,36] Der hen. [18] Andererseits werden die Resonanzen der β-Pyridinprotonen (orange) und der Protonen des zentralen aromatischen Rings (schwarz) zu höheren Feldern verschoben, diagnostisch für aromatische Wechselwirkungen.…”

“…Darüber hinaus ist die Selbstorganisation von 1A nur geringfügig retardiert (kurze Verzögerungszeiten<3 min), was auf eine unwirksame kinetische Abfangung der Monomere mittels intramolekularer H‐Brücken hindeutet. Dies überrascht, in Anbetracht der Tatsache, dass der freie Ligand (Präkursor für Komplex 1 ) aufgrund der Bildung von zwei metastabilen Spezies eine stark verzögerte SP durchläuft: Dessen metastabile Monomer‐Konformere “c 1 ” und “c 2 ” bilden zunächst ein weiteres metastabiles Intermediat (Dimer, bei dem alle H‐Bindungsstellen gesättigt sind) bevor die SP‐Elongation erfolgt [33] . Wir vermuten, dass verschiedene strukturelle Aspekte für das unterschiedliche Verhalten von Komplex 1 verantwortlich sind.…”