Metal Coordination Stoichiometry Controlled Formation of Linear and Hyperbranched Supramolecular Polymers

Abstract

Controlling the topologies of polymers is a hot topic in polymer chemistry because the physical and/or chemical properties of polymers are determined (at least partially) by their topologies. This study exploits the host-guest interactions between dibenzo-24-crown-8 and secondary ammonium salts and metal coordination interactions between 2,6-bis(benzimidazolyl)-pyridine units with metal ions (Zn(II) and/or Eu(III) ) as orthogonal non-covalent interactions to prepare supramolecular polymers. By changing the ratios of the metal ion additives (Zn(NO3 )2 and Eu(NO3 )3 ) linkers to join the host-guest dimeric complex, the linear supramolecular polymers (100 mol% Zn(NO3 )2 per ligand) and hyperbranched supramolecular polymers (97 mol% Zn(NO3 )2 and 3 mol% Eu(NO3 )3 per ligand) are separately and successfully constructed. This approach not only expands topological control over polymeric systems, but also paves the way for the functionalization of smart and adaptive materials.

Tunable Adhesion from Stoichiometry-Controlled and Sequence-Defined Supramolecular Polymers Emerges Hierarchically from Cyanostar-Stabilized Anion–Anion Linkages

“…Previous studies have demonstrated that variation in the reaction stoichiometry of the monomers can control various features of supramolecular polymers. These include the topology by toggling between linear and cross-linked states, − and net chirality. − Use of the stoichiometry to control the sequences in linear supramolecular polymers, however, remains nascent. The role of stoichiometry is well established in small molecule chemistry.…”

“…There are, in general, very few reported examples of using stoichiometry control. Among them, the closest involves addition of 3 mol % of Eu 2+ to a linear zinc-coordinated supramolecular polymer to drive cross-linking . In pioneering work from Sessler, stoichiometry was evident when using cationic macrocycles, called “Texas-sized” boxes, combined with terephthalate monoanions where changing the monomer ratio from 3:2 to 1:1 drove a transition from a small-molecule complex to a supramolecular polymer.…”

Crown Ether‐Based Supramolecular Polymers: From Synthesis to Self‐Assembly

“…Yin and co‐workers reported the construction of hyperbranched fluorescent CSP through the orthogonal self‐assembly of the host–guest recognition of DB24C8‐dibenzylammonium salt and metal coordination of 2,6‐bis(benzimidazolyl)‐pyridine‐Zn (II) ( Figure ). [ 94 ] In detail, an A 2 ‐type homoditopic monomer 98 containing two DB24C8 groups and an AB 2 ‐type heterotritopic monomer 99 containing a dibenzylammonium salt group and two benzimidazole groups were first synthesized. Specifically, the addition of 100% Zn(NO 3 ) 2 to the mixture of 98 and 99 caused the formation of a linear CSP 101 , while the addition of 3% Eu(NO 3 ) 2 and 97% Zn(NO 3 ) 2 resulted in the formation of a hyperbranched CSP 103 .…”

“…Adapted with permission. [94] Copyright 2016, Wiley-VCH GmbH. [96] Copyright 2015, The Royal Society of Chemistry.…”

“…Figure 35. The chemical structure of the monomers 98 and 99, and the graphical representation of the formation of linear and hyperbranched CSPs 101 and 103.Adapted with permission [94]. Copyright 2016, Wiley-VCH GmbH.…”