Toward Anion−π Interactions Directed Self-Assembly with Predesigned Dual Macrocyclic Receptors and Dianions

Abstract

Realizing anion−π interaction induced self-assembly with charge-neutral π receptors as building components is extremely challenging. We designed and synthesized a series of bisoxacalix[2]arene[2]triazines 7−11 in which two macrocyclic motifs are linked in diverse branching angle and rigidity. Crystal structures showed the use of rigid linkers is able to control the orientation of the two macrocyclic cavities. The interplay between the two cavities was revealed by binding studies of 8−11 with chloride in solution. Whereas 180°-and 120°branched hosts 8 and 9 possess dual complexation ability, 60°-branched and flexibly linked hosts 10 and 11 only form 1:1 complex with chloride. Association and self-assembly of these bismacrocyclic building units with dianionic naphthalene-1,5-disulfonate were systematically investigated. The formation of oligomeric self-assemblies and large aggregates in solution was suggested by 1 H NMR titrations, concentration-and temperature-variable 1 H NMR, diffusion-ordered spectroscopy (DOSY), ESI-MS, and dynamic light scattering (DLS). The anion−π induced long-distance self-assembly with coherent particle formation was revealed by SEM, TEM, cryo-TEM, and AFM techniques. The systematic studies allowed us to draw the conclusion that the dianion served to bridge the initial host aggregates through anion−π interactions and was responsible for the coherent particle formation. The cavity orientation of the bismacrocycle components was found to have a significant influence on the coherent particle morphology.

Synthesis ofi‐Corona[6]arenes for Selective Anion Binding: Interdependent and Synergistic Anion–π and Hydrogen‐Bond Interactions

“…We showed previously that 1,3‐alternate oxacalix[2]arene[2]triazine 1 [26, 27] (Figure 1) is a unique electron‐neutral receptor for anions owing to its V‐shaped cleft to accommodate an anion by the formation of anion–π interactions between anion and triazine rings [14, 17] . The anion‐π interactions in complexation of oxacalix[2]arene[2]triazine derivatives with anions have also been demonstrated successfully in the fabrication of assembled structures, [23, 24] responsive vesicles [23] and anion sensing systems [22, 28] . Seeking for anion receptors which would also serve as the potential building units for the construction of artificial anion channels, we have recently devised coronarenes, [29–34] a new type of macrocyclic compounds.…”

“…Anion-p interactions, [10][11][12] attraction between chargeneutral electron-deficient aromatic systems and anions,h ave been recognized as the nascent and important non-covalent bond interactions since the generality,b inding strength and binding models were unveiled experimentally [13][14][15][16][17] and computationally [18][19][20] in recent years.T hey have been utilized as the driving force to enable anion recognition and sensing, [21,22] molecular assembly [23,24] and catalysis. [12,25] Notably,i nt he typical anion-p interaction motif,t he anion is located just above the centroid of electron-deficient aromatic ring.…”

Synthesis ofi‐Corona[6]arenes for Selective Anion Binding: Interdependent and Synergistic Anion–π and Hydrogen‐Bond Interactions

“…We showed previously that 1,3-alternate oxacalix [2]arene- [2]triazine 1 [26,27] (Figure 1) is au nique electron-neutral receptor for anions owing to its V-shaped cleft to accommodate an anion by the formation of anion-p interactions between anion and triazine rings. [14,17] Thea nion-p interactions in complexation of oxacalix [2]arene [2]triazine derivatives with anions have also been demonstrated successfully in the fabrication of assembled structures, [23,24] responsive vesicles [23] and anion sensing systems. [22,28] Seeking for anion receptors which would also serve as the potential building units for the construction of artificial anion channels,wehave recently devised coronarenes, [29][30][31][32][33][34] anew type of macrocyclic compounds.C onstituted by para-(het)arylenes and heteroatoms in an alternative manner, coronarenes adopt coronary conformation with cylindroid cavities.F or example,O 6corona [3]arene [3]tetrazine 2 ( Figure 1) gives ar egular hexagonal structure with three tetrazine rings and six oxygen atom linkages form almost aplane while the three phenylene Figure 1.…”

Amphiphilic Organic Cages: Self‐Assembly into Nanotubes and Enhanced Anion‐π Interactions

“…Cage 1 was synthesized by grafting three hydrophilic moieties onto a hydrophobic organic cage precursor bis(tetra‐oxacalix[2]arene[2]triazine) (Scheme ). This cage precursor was chosen as it has a rigid skeleton and three V‐shaped electron‐deficient clefts, which works as efficient anion receptor . Typically, half cage 1 was first prepared via the reaction of phloroglucinol with excessive amount of cyanuric chloride in the presence of diisopropylethylamine (DIPEA) at 0 °C.…”