Alkyl Bridge Length to Bias the Kinetics and Stability of Consecutive Supramolecular Polymerizations

Abstract

Herein, the impact of alkyl bridge length is unraveled on the self‐assembly of N‐annulated perylenetetracarboxamides 1–4 that cooperatively form supramolecular polymers. Spectroscopic studies in different solvents as media for the self‐assembly demonstrate the impact that the length of the bridge separating the two amide groups of compounds 1–4 exerts on the supramolecular polymerization process: i) in MCH/Tol (8/2), compounds 1–3 exhibit a consecutive process that, however, it is not operative for 4; ii) the presence of three methylene units in 2, which can induce a parallel distribution of the amide groups, notably decreases the stability of the corresponding aggregates in Tol; iii) increasing the spacer length accelerates the conversion of the metastable, intramolecularly H‐bonded monomeric species, which prevents to develop seeded supramolecular polymerizations; iv) the presence of a spacer with five methylene units in 4 hinders the formation of the corresponding 10‐membered pseudo‐cycle; and v) only the higher relative stability of the inactivated monomeric species of 1 enables pathway complexity, with a kinetically controlled self‐assembly to yield nanoparticles and a thermodynamically controlled supramolecular polymerization to achieve fibrillar structures. The results presented herein expand the knowledge on the structure/property relationship for self‐assembling units to provide pathway complexity and to bias the kinetics and stability of the supramolecular aggregates.

Pathway and Length Control of Supramolecular Polymers in Aqueous Media via a Hydrogen Bonding Lock

“…To date, design strategies for pathway control in self‐assembly have primarily relied on: 1) the length modification of a given molecular fragment; [4c,d,f,g,k] 2) the rational placement of functional groups to trigger additional attractive or repulsive interactions; [4a,h,j,l,m,w, x ] and 3) the competition between intra‐ and intermolecular hydrogen bonding (H‐bonding) [4n–v,ac,ad] . The majority of these approaches have been applied to supramolecular systems in organic non‐polar media, where H‐bonding patterns are particularly stable [3]…”

“…Inspired by the use of flexible amides to tune competing intra‐ vs. intermolecular H‐bonds in nonpolar media, [4n–v,ac,ad] we selected a terminal N ‐(2‐hydroxyethyl)amide group as new supramolecular synthon and placed it on the 2‐position of a π‐extended amphiphilic BODIPY dye that carries hydrophilic triethylene glycol (TEG) chains on the opposite molecule side (compound 1 in Scheme 1). The choice of a planar and sterically unhindered BODIPY dye as structural motif was made based on the tendency of this class of dyes to readily self‐assemble via π–π interactions [13] .…”

Influence of the Z/E Isomerism on the Pathway Complexity of a Squaramide‐Based Macrocycle

“…One of the strategies to generate kinetically trapped supramolecular polymorphs consists of using molecules displaying two (or more) markedly distinct interaction patterns competing for the formation of two (or more) distinct assemblies. [ 38–50 ] For instance, Würthner and coworkers reported on an amide‐functionalized perylene bisimide dye able to self‐assemble into three supramolecular polymorphs via three different hydrogen bonding (H‐bonding) motifs inducing different π−π interaction profiles. [ 39 ] This kind of interaction versatility has also been observed in N ‐heterotriangulene dyes [ 49 ] and Pt complexes, [ 50 ] that rely on symmetry aspects and cis/trans coordination isomerism, respectively, to constitute different assembled isoforms.…”

Pfad‐ und Längenkontrolle von supramolekularen Polymeren im wässrigen Medium mittels eines Wasserstoffbrückenschlosses

“…Bisher stützten sich Designstrategien für die Pfadwegkontrolle bei der Selbstorganisation hauptsächlich auf: 1) die Längenmodifikation eines bestimmten Molekülfragments; [4c,d,f,g,k] 2) die rationale Platzierung funktioneller Gruppen, um zusätzliche attraktive oder abstoßende Wechselwirkungen auszulösen, [4a,h,j,l,m,w, x ] und 3) die Konkurrenz zwischen intra‐ und intermolekularen Wasserstoffbrückenbindungen (H‐Bindung) [4n–v,ac,ad] . Die meisten dieser Ansätze wurden auf supramolekulare Systeme in organischen unpolaren Medien angewendet, in denen H‐Bindungsmuster besonders stabil sind [3]…”

“…Inspiriert von der Verwendung flexibler Amide zur Induktion konkurrierender intra‐ und intermolekularer H‐Bindungen in unpolaren Medien, [4n–v,ac,ad] haben wir eine terminale N ‐(2‐Hydroxyethyl)amid‐Gruppe als neues supramolekulares Synthon gewählt und dieses an der 2‐Position eines π‐erweiterten amphiphilen BODIPY‐Farbstoffes platziert. Auf der gegenüberliegenden Seite dieses Synthons trägt die Verbindung 1 hydrophile Triethylenglycol (TEG)‐Ketten (Schema 1).…”