Cation Binding by Lariat Ethers

Thermodynamic parameters derived from calorimetry for metal ion binding by a range of aza-oxa lariat ethers and BiBLE s with amide side-arms (3.52 and 3.53) is shown in Table 3.7. Coordination occurs via the macrocycle and amide oxygen atom. The longer chain side arms 3.52b and 3.53b are 

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Figure 18. AH-TAS plot for cation binding by lariat ethers.

Sodium Cation Binding by Nitrogen-pivot. Lariat Ethers... 

Figure 1. Cation binding by 12-, i5-, and 18-membered ring, nitrogen-pivot lariat ethers. Ring sizes triangles, 12 squares, 15 circles, 18. Cations filled symbols, IVa+ open symbols, NH4+.

Kaifer. A. Echegoyen, L. Gustowski. D. Goli, D.M. Gokel. G.W. Enhanced sodium cation binding by electro-chemically-reduced, nitrobenzene-substituted lariat ethers. J. Am. Chem. Soc. 1983. 105. 7168-7169. 

Intramolecularity in lariat ether complexation was demonstrated in three ways. First, when solution cation binding constants were determined. Kg was shown to be independent of cation and macrocycle concentrations (within certain limits). The efficacy of complexation of a single cation by two macrorings [(ML2) complex formation] should be concentration dependent. Second, ammonium cation binding constants were determined for the series (see above) of monoaza-15-crown-5 and -18-crown-6 compounds having (CH2CH20)jiClH3 (n 0 to 8) sidearms (31). 

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