Supramolecular assemblies of azobenzene‐β‐cyclodextrin dimers and azobenzene modified polycaprolactones

Abstract

Click chemistry is employed to couple two β-cyclodextrins at both ends of azobenzene moiety yielding dumbbell-shaped amphiphiles (AZO-β-CD dimer) constructed by rigid aromatic building blocks as "body", and hydrophilic cyclodextrins as "head" with almost quantitative yield and purity. Bulk aggregates formed by the self-assembly of the supraamphiphiles through π-π stacking and hydrophobic effect are observed. Meanwhile, the rationally designed polyesters, named as AZO-PCL with controllable molecular weights and low polydispersities, are successfully synthesized by ring-opening polymerization of ε-caprolactone in the presence of p-aminoazobenzene as initiator. In the aqueous phase, very stable spherical particles are formed by host-guest interactions between AZO-β-CD and AZO-PCLs; the spherical aggregates inherit the photo-responsiveness of azobenzene. The detailed aggregation and disaggregation behaviors are fully investigated by TEM, SEM, NMR, 2D NOESY, IR, UV and XRD measurements. Compared to the previous works, our newly developed system can be fabricated with more readily manners, avoiding tedious synthetic process; the reversible and dynamic nature of the non-covalent interactions also can be modulated alternatively by UV or visible light. Thus, such dumbbell-shaped supra-amphiphiles are of great potential applications in the controlled delivery systems.

Azo group(s) in selected macrocyclic compounds

“…86 ), which interacts as a “dimer” with azo bearing polyester obtained in reaction of ε-caprolactone with p -aminoazobenzene (AZO-PCL) (Fig. 86 a), was described by Ma et al [ 254 ]. It was suggested that in aqueous solution micellar aggregates are formed due to host–guest interaction between (AZO-β-CD) and AZO-PCL (Fig.…”

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Fig. 86 a The synthesis of AZO-β-CD by click reaction, b AZO-β-CD/AZO-PCL supramolecular complex, and c the possible aggregation mode: spherical particles are formed by host–guest interactions between AZO-β-CD and AZO-PCLs [ 254 ]

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Unorthodox β-Cyclodextrin-Based AIE-Active Probes for Living Cell Imaging in the Absence of Fluorophore Units and Related Mechanism Exploration

“…Therefore, the schematic representation of a tentative aggregation mode is described in Figure 7 based on the combination of the layered morphology and the results of temperature-variable 1 H NMR. A large number of hydroxy, the secondary amino, and amide groups of β-CD dimers could form strong and stable intermolecular hydrogen bonds, which resulted in the compact aggregation 43 and layered structure. As we discussed above, it could be believed that in the aggregation states, the amide and hydroxyl units in the β-CD dimers might form through-bond and through-space electronic conjugations because of the multiple hydrogen-bonding interactions.…”

Redox-Sensitive Polymer Micelles Based on CD44 and Folic Acid Receptor for Intracellular Drug Delivery and Drug Controlled Release in Cancer Therapy

“…Mono-6-deoxy-6-(p-tolylsulfonyl)-β-cyclodextrin (β-CD-OTs) were synthesized as previously described . β-CD (21.00 g, 18.50 mmol) was dissolved in 150 mL water, then slowly added the sodium hydroxide (1.86 g, 0.047 mmol).…”

“…The mixture was heated at 80 °C for 24 h, cooled to room temperature, dialyzed (MWCO 3500 Da), and Mono-6-deoxy-6-(p-tolylsulfonyl)-βcyclodextrin (β-CD-OTs) were synthesized as previously described. 39 β-CD (21.00 g, 18.50 mmol) was dissolved in 150 mL water, then slowly added the sodium hydroxide (1.86 g, 0.047 mmol). After it was completely dissolved, p-toluenesulfonyl chloride (TsCl) (3.16 g, 16.60 mmol) was added into the ice−water bath to control the reaction temperature.…”