2:2 Complexes from Diphenylpyridiniums and Cucurbit[8]uril: Encapsulation‐Promoted Dimerization of Electrostatically Repulsing Pyridiniums

Abstract

Rigid linear compounds G1 and G2, which contained two 4-phenylpyridinium (PhPy ) units, have been prepared to investigate their binding with cucurbit[8]uril (CB[8]). X-ray crystallographic structures revealed that in the solid state both compounds were included by CB[8], through antiparallel stacking, to form 2:2 quaternary complexes (G1) @(CB[8]) and (G2) @(CB[8]) . For the former complex, CB[8] entrapped G1 by holding two heterodimers of its Py and benzyl units, which were at opposite ends of the backbone. In contrast, for the first time, the second complex disclosed parallel stacking of two cationic Py units of G2 in the cavity of CB[8] in the solid state, despite the generation of important electrostatic repulsion. Isothermal titrations in water afforded high apparent association constants of 4.36×10 and 6.43×10 m for 1:1 complexes G1@CB[8] and G2@CB[8], respectively, and H NMR spectroscopy experiments in D O confirmed a similar stacking pattern to that observed in the solid state. A previous study and crystal structures of the 2:1 complexes formed between three new controls, G3-5, and CB[8] did not display such unusual stacking of the cationic Py unit; this may be attributed to the multivalency of the two CB[8] encapsulation interactions.

Controlling the structure and photophysics of fluorophore dimers using multiple cucurbit[8]uril clampings

“…a molecule with signicant rigidity. 28,29 For instance, various rigid molecular moieties such as benzidine, 30 benzothiazole, 31,32 arylpyridinium, 28,33 arylterpyridyl, 34 bipyridinium, 35 and benzimidazole 29 have been employed to produce CB[8]-mediated 2 : 2 complexes. Herein, we present a general and modular strategy towards the dimerization of arbitrary functional components (uorophores in this work) by connecting them to multiple rigid modules that can be "clamped" together by CB [8] complexation.…”

A cucurbit[8]uril-stabilized 3D charge transfer supramolecular polymer with a remarkable confinement effect for enhanced photocatalytic proton reduction and thioether oxidation

“…When an electron-rich aromatic unit is connected to an electron-deficient aromatic unit with a short linker that does not allow for intramolecular interaction, the resulting ditopic molecule may stack to form a homodimer stabilized by two intermolecular donor-acceptor interactions or charge transfer complexations. [46][47][48][49][50][51] The encapsulation of one CB [8] macrocycle for the single donor-acceptor complex can further stabilize the whole dimer through multivalency. 52,53 54 To develop a new binding motif to fabricate highly stable 3D supramolecular polymers in water, we designed and synthesized a tetrahedral compound T1 which bears four hydrophilic diglycol chains (Scheme 1).…”

“…We previously reported the generation of water-soluble, three-dimensional supramolecular polymers from the coassembly of cucurbit [8]uril (CB [8]) and rationally designed multitopic building blocks, [43][44][45] which is driven by the encapsulation of the CB [8] macrocycle for intermolecular homodimers of peripheral hydrophobic aromatic units of the multitopic building blocks. [30][31][32] Given the high stability of the 2 + 2 complexation patterns formed between CB [8] and elongated aromatic guests, [46][47][48][49][50][51] we envisioned that the implementation of this enhanced binding motif might lead to the generation of new, highly stable 3D supramolecular polymers that exhibit unique functions. We herein describe that a tetraphenylmethane-cored compound that bears four donor-acceptor-type side arms can co-assemble with CB [8] in water to form a highly stable charge transfer complexation-based porous supramolecular polymer, which exhibits a remarkable confinement effect in water for enhanced visible light-induced proton reduction and thioether oxidation to afford hydrogen gas and a sulfone.…”

A pore-expanded supramolecular organic framework and its enrichment of photosensitizers and catalysts for visible-light-induced hydrogen production

“…Tetrahedral compound M1 was used for the generation of the expanded 3D SOF. Within the cavity of CB[8], it was expected that fully eclipsed anti-parallel stacking of two BPB units would be disfavored due to the electrostatic repulsion of the pyridinium units ( Figure 1) [17], instead a slipped anti-parallel stacking was expected, from which the formation of new expanded 3D framework would occur [18]. For the synthesis of M1 (Scheme 1), compound 3 was prepared from the reaction of 1 [19] and 2 [20] in hot DMF, followed by treatment with an excess of methyl iodide in MeCN under reflux.…”