Revising Complex Supramolecular Polymerization under Kinetic and Thermodynamic Control

Abstract

Pathway complexity, hierarchical organization, out of equilibrium, and metastable or kinetically trapped species are common terms widely used in recent, high‐quality publications in the field of supramolecular polymers. Often, the terminologies used to describe the different self‐assembly pathways, the species involved, as well as their relationship and relative stability are not trivial. Different terms and classifications are commonly found in the literature, however, in many cases, without clear definitions or guidelines on how to use them and how to determine them experimentally. The aim of this Minireview is to classify, differentiate, and correlate the existing concepts with the help of recent literature reports to provide the reader with a general insight into thermodynamic and kinetic aspects of complex supramolecular polymerization processes. A good comprehension of these terms and concepts should contribute to the development of new complex, functional materials.

N‐Annulated Perylene Bisimides to Bias the Differentiation of Metastable Supramolecular Assemblies into J‐ and H‐Aggregates

“…[1] To mimic their behavior, an accurate comprehension of the kinetics associated with self-assembly is required. Thus,i nt he quest of models to replicate nature,p athway complexity in supramolecular chemistry [2] is playing acrucial role even though we are still far from the complexity exhibited by natural systems. Supramolecular polymers,d ynamic entities resulting from noncovalent junctions between monomeric species,constitute av ery useful benchmark in this field.…”

“…[2,3b, 4] Te rms such as metastable monomers, [5] off-and on-pathway aggregates, [6] supramolecular polymorphism, [7] fueled aggrega-tion, [8] and consecutive or competitive SP [9] are associated with complex self-assembly phenomena investigated in connection with supramolecular polymers.Inmany of these SPs, akinetically controlled aggregate evolves over time,oraided by the addition of seeds,tothe thermodynamically controlled aggregate. [2] However,s ystems of higher complexity are also reported. Remarkable examples of self-assembling pathway complexity are the three different luminescent aggregates formed by Pt II complexes, [10] the 1D or 2D aggregates yielded by zinc porphyrins, [11] or the three 1D supramolecular polymorphs formed by perylene bisimides (PBIs) endowed with chiral side chains.…”

Impact of Positional Isomerism on Pathway Complexity in Aqueous Media

“…As also shown previously by UV/Vis, kinetically controlled species A readily converts to the thermodynamic product B simply by keeping the 20 μ m aqueous aggregate solution of A at room temperature over the period of approximately one day (Figure g). This transformation can be accelerated by increasing concentration and/or temperature (see plot of Abs 615 vs. time in Figure h), which is typical for the consecutive transformation of an on‐pathway species . Therefore, A converts into B via a rearrangement of the dye molecules within the aggregate, which does not involve the disassembly into free monomeric species.…”

“…Control over the competing aggregation pathways in these molecular systems is typically achieved by optimization of sample preparation protocols. These processes are generally tedious and often require a very specific set of experimental conditions (that is, concentration, temperature, solvent composition, and others) . Alternatively, these complex sample preparation methods could be simplified by molecular design strategies, which have been recently introduced to broaden the scope of pathway complexity.…”

Controlled Supramolecular Polymerization of d8 Metal Complexes through Pathway Complexity and Seeded Growth

“…[6,7,12,13] However, predicting and controlling competing aggregation pathways by molecular design represents a major challenge in the field of self-assembly, as evident from the limited amount of literature dealing with this topic. For a comprehensive overview of the recent advances in the field of kinetic vs. thermodynamic self-assembly process, we refer the readers to recent reviews by the groups of Würthner, [14] Perrier, [15] Meijer, [16] Fernández and Sánchez, [17] and de Greef and Hermans. [18] To date, thorough studies to unravel the interplay between kinetics and thermodynamics in self-assembled systems have almost exclusively focused on purely organic π-conjugated systems.…”