Lariat crown ethers

Lariat ethers of structure 8 were found to be selective toward Li ion and the lariat crown ether-Li+ complexes are more stable than the corresponding complexes with Na or K+, in methanol. Nevertheless, experiments conducted in aqueous solution showed that Na+ had a better complexation ability than the other two alkali metal cations. Hence, selective complexation of lariat crown ethers with cations changes with the solvent system this may be due in part to the difference in solvation between solvent and cation (Figure 9 f. ... 

Several new lariat-crown ethers have been reported bearing either bridged bis-dioxin 94 or tetraoxaadamantane units 95 as chiral substituents however, they were used only for the transportation of metal ions into organic solvents <2003M509>. 

McPhee, M. M. Kern, J. T. Hoster, B. C. Kerwin, S. M, (2000) Propargylic sulfone-armed lariat crown ethers alkali metal ion-regulated DNA cleavage agents Bioorg. Chem. 8, 98-118. 

Gokel for reducible quinone (25, 26) and nitroaromatic (32, 33) lariat crown ethers with alkali metal guest cations discussed earlier. Support for the latter effect comes from the related ligand system (81), containing no amide carbonyl groups, and electrochemical results revealing... 

Fig. 4.37. Chemical structures of some lariat crown ethers.

Lariat crown ethers with two terminal pyrenyl sidearms connected to the same carbon 103 (/= 0, 1 m = 0-2 n = 0-2) or to two different carbon atoms 104 (m = 0-2 n 1,2) and 105 (m 0, 1) showed intramolecular excimer emission in the free state (Jt-Jt-stacking of the pyrene rings), whose intensity decreases with the increase of monomer emission intensity upon metal ion complexation <20020L2641, 2004JOC4403>. This response has been ascribed to the cooperative participation of one of the two sidearms in the complexation of the crown ring with the metal ion, which renders inoperative the Jt-Jt-stacking of aromatic rings. Most of these fluorophores show alkaline earth over alkali metal ion selectivities. 

Gokel and coworkers prepared a series of nitrogen-pivot lariat crown ethers (Schultz et al., 1985). These compounds all have side arms connected to a... 

Lanthanide complexes, 10. 11. 20 Large cavity peraza-crown macrocycles. 6. 7 Lariat crown ethers, 1. 10, 20, 102, 153, 259, 546... 

Julian, R.R. and Beauchamp, J.L. (2002) The unusually high proton affinity of aza-18-crown-6 ether implications for the molecular recognition of lysine in peptides by lariat crown ethers. Journal of the American Society for Mass Spectrometry, 13, 493 98. 

Figure 11 (a) X-ray crystal structures of cation-jr interactions between Na+ and indole of a lariat crown ether and (b) five-component... 

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