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13C NMR relaxation times (T1s) have been determined for monoazacrown ethers (CA15C5 and CA18C6) and bis(monoazacrown ether)s (BCA15C5, BCA18C6, BOA15C5, and BOA18C6) in the absence and presence of Na+and K+ ions. For the monoazacrown ethers with heptyl side chain and the bis(monoazacrown ether)s with pentamethylene bridge chain marked changes in T1 values are observed upon the complexation, and the changes are dependent on the cation and on the structure of the ligands. The complexation with Na+ ion can give a larger effect on the T1 values for the bis(monoazacrown ether)s of 15- and 18-membered rings, especially on the mobility of the bridging chain carbons, which is indicative of the formation of an intramolecular sandwich complex. On the other hand, the present T1 study again shows the prominent effect of the oxygen in the bridging chain on the complexation of BOA15C5 and BOA18C6. Small differences in T1 values obtained between Na+ complexes and K+ complexes of these two bis(crown ether)s suggest that ...

Trisubstituted phenols having two bulky groups at 2,6-position and pKa value below 7 proved to be good cooperative carriers in solvent extraction and liquid membrane transport of alkali-metal cations with crown ethers.

A new ‘double-cycle’ mechanism is presented for the N-octadecylmonoazacrown ether mediated cation transport to an acidic receiving phase cooperated with 2,6-di(t-butyl)-4-nitrophenol. The occurrence of the novel process may be attributable to the lower acidity of the phenol and aggregation behavior of the protonated monoazacrown ethers in the membrane phase.

New bis(crown ether)s 3 consisting of a benzocrown unit and a monoazacrown unit connected by an oxyethylene linkage were synthesized. Their complexation behavior proved to be analogous to that of lariat monoazacrown ethers rather than that of bis(benzocrown ether)s.

Vertical arrangement of the alkyl side arm in the crystal structure of KSCN complex of N-heptylmonoaza-18-crown-6 is well-consonant with the effective side-arm participation in N-pivot lariat ether complexes and supports the lack of ‘biscrown effect’ for bis(monoaza-18-crown-6)s.