Search

A water-soluble 2,6-helic[6]arene derivative was conveniently synthesized, and it showed strong binding abilities towards quaternary phosphonium salts in aqueous solution. Moreover, an acid/base controlled switchable complexation process was also described. [ABSTRACT FROM AUTHOR]

Complexation of racemic 2,6-helic[6]arene 1 and its hexamethyl-substituted derivative 2 with quaternary ammonium salts, N-heterocyclic salts, and tetracyanoquinodimethane have been described in detail. It was found that host 2 could form stable complexes with acetyl choline, thiaacetyl choline, N, N, N-trimethylbenzenammonium salt, pyridinium, and 4,4′-bipyridinium salts in solution and/or in the solid state. The unsubstituted macrocycle 1 showed more significant complexation with the widely tested quaternary ammonium salts and N-heterocyclic salts, and exhibited stronger complexation towards the guests than its derivative 2. Moreover, it was found that macrocycle 1 and its derivative 2 could also complex with neutral electron-deficient tetracyanoquinodimethane (TCNQ), and the association constants were determined to be 2840±94 and 1358±46 m−1, respectively. These results could make this new macrocycle and its derivatives find wide applications in the design and construction of functional supramolecular assemblies. [ABSTRACT FROM AUTHOR]

Charge-transfer (CT) complexes formed from 2,6-helic[6]arene hosts and a tropylium cation are described in detail. In particular, it was found that the binding and release processes of the guest in the complexes could be efficiently controlled by a redox stimulus, and the responsive process could be visually observed by the color change of the solution. To our knowledge, this represents the first visible redox stimulus-responsive host–guest system formed from the tropylium cation. [ABSTRACT FROM AUTHOR]

A new class of chiral macrocyclic arene composed of three chiral 2,6-dihydroxyltriptycene subunits bridged by methylene groups was designed and synthesized. Structural studies showed that the macrocyclic molecule adopts a hex-nut-like structure with a helical chiral cavity and highly fixed conformation. Efficient resolution was achieved through the introduction of chiral auxiliaries to give a couple of enantiopure macrocycles, which exhibited high enantioselectivity towards three pairs of chiral compounds containing a trimethylamino group. [ABSTRACT FROM AUTHOR]

A route to enantiopure ( O-methyl) 6 -2,6-helic[6]arenes (+)- P-2 and (-)- M-2 has been provided. By the reaction of enantiopure triptycene precursors (+)-1 and (-)-1 in refluxed o-DCB for 12 h in the presence of catalytic amount of FeCl 3 , and then followed by treatment of the obtained oligomers under the same conditions, (+)- P-2 and (-)- M-2 could be obtained in 51% and 53% total yield, respectively. It was also found that racemic and enantiopure ( O-methyl) 6 -2,6-helic[6]arenes could be easily brominated by Br 2 to give the corresponding hexabromo-substituted helic[6]arene derivatives rac-4, (+)- P-4, and (-)- M-4 in high yields. The crystal structure of (+)- P-4 further confirmed the absolute configuration of the helic[6]arenes and their derivatives. Moreover, a series of hexaaryl-substituted helic[6]arene derivatives 5a-f with deepened cavities could be conveniently synthesized in 55-71% yield by Suzuki-Miyaura coupling reactions of 4 and arylboronic acids. rac-5a could encapsulate chloroform and exhibit self-sorting stacking in solid state. Enantiopure (+)- P-5a-f and (-)- M-5a-f showed mirror images in their CD spectra.