Complexation of lithium(I), sodium(I), silver(I) and thallium(I) by 4,7,13,16-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane and 4, 7, 13-trioxa-1,10-diazabicyclo[8.5.5]eicosane in trimethyl phosphate. A potentiometric titration and Li and Na nuclear magnetic resonance study

Complexation of M⁺=Li⁺, Na⁺, Ag⁺ and TI⁺ by the cryptands 4, 7, 13, 18-tetraoxa-l, 10-diazabicyclo[8.5.5]eicosane (C211) and 4,7,13-trioxa-1,10-diazabicyclo[8.5.5]eicosane (C21C₅) to form the cryptates [M.C211]⁺ and [M.C21C₅]⁺ has been studied in trimethyl phosphate by potentiometric titration and ⁷Li and ²³Na NMR spectroscopy. For [M.C211]⁺ the logarithm of the apparent stability constants, log K (dm³ mol^-1)=6.98±0.05, 5.38±0.05, 9.82±0.02 and 3.95±0.02 for M⁺ =Li⁺, Na⁺, Ag⁺ and TI⁺, respectively; and for [M.C21C₅]⁺ log K (dm³ mol^-1)=2.40±0.10, 1.90±0.05, 6.04±0.02 and 2.42±0.10 for M⁺=Li⁺, Na⁺, Ag⁺ and Tl⁺, respectively. The decomplexation kinetic parameters for [Na.C211]⁺ are: k_d (298.2 K)=6.924±0.50 s^-l, ΔH_d≠=62.2±0.9 kJ mol^-1, and ΔS_d≠= -20.3±2.7 J K^-1 mol^-1; and those for [Li.C21C₅]⁺ are: k_d (298.2 K)=23.3±0.4 s^-1, ΔH_d≠ =61.2±1.1 kJ mol^-1, and ΔS_d≠= -13.6±3.6 J K^-1 mol^-1. Metal ion exchange on [Li.C211]⁺ is in the very slow extreme of the NMR timescale up to 390 K and k_d « 4 s^-1 at 298.2 K, while in contrast exchange on [Na.C21C₅]⁺ is in the fast extreme of the NMR timescale at 298.2 K (k_d≈ 10⁴ s^-1). These data are compared with those obtained in other solvents.