97946-28-6Relevant articles and documents
Photoresponsive Crown Ethers. Part 14. Photoregulated Crown-Metal Complexation by Competitive Intramolecular Tail(Ammonium)-biting
Shinkai, Seiji,Ishihara, Midori,Ueda, Kaori,Manabe, Osamu
, p. 511 - 518 (2007/10/02)
New photoresponsive crown ethers (1H+) having a crown ether ring and an ammoniumalkyl +-(CH2)n, n = 4,6,10> group attached to the two sides of an azobenzene have been synthesized.These photoresponsive 'tail-biting' crown ethers have been designed so that intramolecular 'biting' of the ammonium group to the crown can only occur upon photoisomerisation to the cis-forms.In the thermal cis-trans isomerisation, the first-order rate constants for cis-(1H+) were smaller by 1.6 - 2.2 -fold than those for (1) (the analogous free amines).Moreover, this rate increased with increasing added K+ concentration.This suggests that the ammonium tail is intramolecularly bound to the crown ether ring in cis-(1H+).This intramolecular 'biting' is further reflected in the relative affinities of (1H+) for alkali-metal cations.The affinities were markedly reduced by u.v.-light irradiation and in particular, cis-(1H+)(n=6) and cis-(1H+)(n=10) showed almost no metal-binding ability.This marked difference in the metal-binding ability was used to generate the light-controlled systems for the passive or active ion-transport of ions across a liquid membrane.
