Oligoether-strapped calix[4]pyrrole: an ion-pair receptor displaying cation-dependent chloride anion transport.
A ditopic ion-pair receptor (1), which has tunable cation- and anion-binding sites, has been synthesized and characterized. Spectroscopic analyses provide support for the conclusion that receptor 1 binds fluoride and chloride anions strongly and forms stable 1:1 complexes ([1·F](-) and [1·Cl](-)) with appropriately chosen salts of these anions in acetonitrile. When the anion complexes of 1 were treated with alkali metal ions (Li(+), Na(+), K(+), Cs(+), as their perchlorate salts), ion-dependent interactions were observed that were found to depend on both the choice of added cation and the initially complexed anion. In the case of [1·F](-), no appreciable interaction with the K(+) ion was seen. On the other hand, when this complex was treated with Li(+) or Na(+) ions, decomplexation of the bound fluoride anion was observed. In contrast to what was seen with Li(+), Na(+), K(+), treating [1·F](-) with Cs(+) ions gave rise to a stable, host-separated ion-pair complex, [F·1·Cs], which contains the Cs(+) ion bound in the cup-like portion of the calix[4]pyrrole. Different complexation behavior was seen in the case of the chloride complex, [1·Cl](-). Here, no appreciable interaction was observed with Na(+) or K(+). In contrast, treating with Li(+) produces a tight ion-pair complex, [1·Li·Cl], in which the cation is bound to the crown moiety. In analogy to what was seen for [1·F](-), treatment of [1·Cl](-) with Cs(+) ions gives rise to a host-separated ion-pair complex, [Cl·1·Cs], in which the cation is bound to the cup of the calix[4]pyrrole. As inferred from liposomal model membrane transport studies, system 1 can act as an effective carrier for several chloride anion salts of Group 1 cations, operating through both symport (chloride+cation co-transport) and antiport (nitrate-for-chloride exchange) mechanisms. This transport behavior stands in contrast to what is seen for simple octamethylcalix[4]pyrrole, which acts as an effective carrier for cesium chloride but does not operates through a nitrate-for-chloride anion exchange mechanism.
Department of Chemistry, Kangwon National University, Chun Cheon, 200-701, Korea.
In-Won
IW
Park
Jaeduk
J
Yoo
Bohyang
B
Kim
Suman
S
Adhikari
Sung Kuk
SK
Kim
Yerim
Y
Yeon
Cally J E
CJ
Haynes
Jennifer L
JL
Sutton
Christine C
CC
Tong
Vincent M
VM
Lynch
Jonathan L
JL
Sessler
Philip A
PA
Gale
Chang-Hee
CH
Lee
D000838:Anions / Q000737:chemistry*; D001665:Binding Sites; D047250:Calixarenes / Q000737:chemistry*; D002412:Cations / Q000737:chemistry*; D002712:Chlorides / Q000737:chemistry*; D043844:Crown Ethers / Q000737:chemistry*; D017136:Ion Transport; D015394:Molecular Structure; D011166:Porphyrins / Q000737:chemistry*; D013329:Structure-Activity Relationship
D000838:Anions; D002412:Cations; D002712:Chlorides; D043844:Crown Ethers; D011166:Porphyrins; C469811:calix(4)pyrrole; D047250:Calixarenes