Higher-generation type III-B rotaxane dendrimers with controlling particle size in three-dimensional molecular switching

Abstract

Type III-B rotaxane dendrimers (T3B-RDs) are hyperbranched macromolecules with mechanical bonds on every branching unit. Here we demonstrate the design, synthesis, and characterization of first to third (G1–G3), and up to the fourth (G4) generation (MW > 22,000 Da) of pure organic T3B-RDs and dendrons through the copper-catalyzed alkyne–azide cycloaddition (CuAAC) reaction. By utilizing multiple molecular shuttling of the mechanical bonds within the sphere-like macromolecule, a collective three-dimensional contract-extend molecular motion is demonstrated by diffusion ordered spectroscopy (DOSY) and atomic force microscopy (AFM). The discrete T3B-RDs are further observed and characterized by AFM, dynamic light scattering (DLS), and mass spectrometry (MS). The binding of chlorambucil and pH-triggered switching of the T3B-RDs are also characterized by 1H-NMR spectroscopy.

A Brief Minireview of poly-triazole: Alkyne and Azide Substrate Selective, Metal-catalyst Design

“…[70][71][72] However, there are still some problems to be solved and the work to be done in the future aftermentioned. [73][74][75][76][77] (i) Currently, the click reaction by cyclic acetylene and azide are relying on ring tension.…”

Soft nanohand grabs a growing nanoparticle

“…Owing to their tunable organic functionalities with ''sticky'' hetero-atoms (O, N, S) at the branching points, these macromolecules can encapsulate various inorganic nanoparticles (NPs) or drug molecules embedded in their internal void space. [2][3][4] Three types of dendrimer/dendroninorganic NP hybrid structures can be distinguished, depending on the ratio of the number of dendrimers/dendrons to the number of NPs (Fig. 1a).…”

Dual stimuli-responsive rotaxane-branched dendrimers with reversible dimension modulation

“…Up to date, a great number of sophisticated rotaxane dendrimers have been successfully prepared by Vögtle and co-workers 25 , Stoddart and co-workers 26 – 28 , Gibson et al 29 , Kim and co-workers. 30 , 31 , Wang and Kaifer 32 , Leung and co-workers 33 , 34 , etc., which have displayed wide applications in the field of molecular nanoreactors, gene delivery, and light-harvesting system, etc. 35 – 37 .…”

“…35 – 37 . It should be noted that, although a great deal of achievement has been obtained in this field, the rotaxane-branched dendrimers, in which rotaxane moieties are located on each branch, have been rarely explored because of the synthetic chanllenge 31 , 33 , 34 , 38 . In particular, the construction of multiple stimuli-responsive rotaxane-branched dendrimers has not been yet realized.…”