Corralarenes: A Family of Conjugated Tubular Hosts

Abstract

Despite the advances in host−guest chemistry, macrocyclic hosts with deep cavities are far from abundant among the large number of wholly synthetic hosts described in the literature. Herein, we describe the design and synthesis of two new tubular hosts, namely, corral[4]arene and corral[5]arene. The former has been isolated and characterized as two conformational diastereoisomers, one is centrosymmetric and the other asymmetric. The latter, a fivefold symmetrical and flexible host, has also been investigated in detail. It is composed of five 4,4′-dimethoxybiphenyl units bridged by ethynylene linkers at their 2,2′-positions and adopts a pentagonal conformation with a tubular-shaped cavity in the presence of guests. This structure endows corral[5]arene not only with a conjugated backbone, capable of bright fluorescent emission (quantum yield, 56%), but also a deep π-electron-rich aromatic cavity with remarkable conformational flexibility. The adaptive cavity of corral [5]arene allows it to accommodate a wide range of neutral and positively charged electron-deficient guests with different molecular sizes and shapes. Binding constants between this host and these guests in three different nonpolar organic solvents lie in the range of 10 3 to 10 7 M −1 . Moreover, corral[5]arene exhibits dynamic chirality on account of the axes of chirality associated with each of the five biphenyl units and displays first-order transformation as exhibited by circular dichroism in response to the addition of chiral guests. All these stereochemical features render corral[5]arene an attractive host for a variety of supramolecular and nanotechnological applications.

Molecular Recognition with Macrocyclic Receptors for Application in Precision Medicine

“…Contrastingly, regular CAs do not display such high binding affinities, and their average association constant is only 10 3.8 M –1 . Moreover, not only CAs with deep cavities but also other deep-cavity macrocyclic receptors bind guests tightly. , Notably, transverse extension of the cavity is ineffective, e.g., the p -sulfonatocalix­[ n ]­arenes (SC n As, n = 4, 5, or 6, Scheme ) exhibit negligible binding to paclitaxel, whereas the respective association constants of the sulfonated azocalix­[ n ]­arenes (SAC n As, n = 4, 5, or 6, Scheme ) with paclitaxel are 4.9 × 10 5 , 2.9 × 10 6 , and 1.1 × 10 6 M –1 . Transverse extension of the cavity even weakens the binding capacity of a macrocyclic receptor; e.g., cucurbit[8]­uril displays smaller association constants than does cucurbit[7]­uril .…”

Water-soluble organic macrocycles based on dye chromophores and their applications

“…It should be mentioned that vastly increasing dye-based macrocycles have been designed, synthesized and fully characterized, though many of them are insoluble in water. However, a considerable number of dye-macrocycles have clear potential to become water-soluble by introducing hydrophilic groups, for example, anthracene-based pagoda[4]arene reported by Chen et al , 47 biphen[ n ]arenes constructed from various dye units developed by Li et al 48 and corralarenes reported by Cai et al 49…”

Cycling a Tether into Multiple Rings: Pt‐Bridged Macrocycles for Differentiated Guest Recognition, Pseudorotaxane Transformations, and Guest Capture and Release

“…Since Pedersen's seminal work on crown ethers, [1, 2] the synthesis of macrocycles has been central to supramolecular chemistry [3] . The library of known ring molecules is vast, encompassing diverse compositions, geometries and sizes [4–9] . Macrocycles are being investigated for applications [10] such as sensing, [11] molecular delivery, [12] molecular machinery, [13] and more [14] …”

“…[3] The library of known ring molecules is vast, encompassing diverse compositions, geometries and sizes. [4][5][6][7][8][9] Macrocycles are being investigated for applications [10] such as sensing, [11] molecular delivery, [12] molecular machinery, [13] and more. [14] Macrocycle synthesis relies on one of the approaches depicted in Figure 1.…”