Alkali-metal complexes of a pendant-arm tetraaza macrocycle. Equilibrium, inter- and intra-molecular exchange processes
作者:Sonya L. Whitbread、Steve Politis、Ashley K. W. Stephens、Jeremy B. Lucas、Ramesh Dhillon、Stephen F. Lincoln、Kevin P. Wainwright
DOI:10.1039/dt9960001379
日期:——
The stabilities log(K/dm3 mol–1) of [ML1]+ formed by 1,4,7,10-tetrakis(2-hydroxyethyl)-1,4,7,10-tetraazacyclododecane (L1) were found to vary with M+ in the sequence Li+(8.07 ± 0.05 and 8.90 ± 0.05), Na+(6.66 ± 0.05 and 7.49 ± 0.05), K+(3.40 ± 0.05 and 5.91 ± 0.05), Rb+(3.00 ± 0.05 and 4.23 ± 0.05), Cs+(2.90 ± 0.05 and 4.04 ± 0.05) and Ag+(9.35 ± 0.04 and 14.00 ± 0.05), in acetonitrile and propylene carbonate, respectively, determined by potentiometric titration at 298.2 K and I= 0.05 mol dm–3(NEt4ClO4). Complexes of the parent macrocycle 1,4,7,10-tetraazacyclododecane (L2) are less stable. For the monomolecular decomplexation of [NaL1]+ in acetonitrile and propylene carbonate the values kd(298.2 K)= 78.5 ± 1.0 and 26.1 ± 0.6 s–1, ΔHd‡= 49.2 ± 0.3 and 57.7 ± 0.4 kJ mol–1, and ΔSd‡=–43.7 ± 0.9 and –24.0 ± 1.0 J K–1 mol–1, respectively, were determined by 23Na NMR spectroscopy. Carbon-13 NMR spectroscopy showed that for the enantiomerisation of square-antiprismatic [LiL1]+, [NaL1]+ and [KL1]+ in methanol, ke(298.2 K)= 18 300 ± 3100, 7100 ± 220 and 7010 ± 200 s–1, ΔHe‡= 41.3 ± 1.3, 24.6 ± 0.5 and 53.7 ± 0.6 kJ mol–1, and ΔSe‡=–24.8 ± 5.9, –88.6 ± 1.8 and 8.8 ± 2.3 J K–1 mol–1, respectively. For [LiL1]+ and [NaL1]+ enantiomerisation occurs much more rapidly than intermolecular exchange of L1, but for [KL1]+ enantiomerisation occurs predominantly through intermolecular exchange of L1.
研究发现,1,4,7,10-四(2-羟乙基)-1,4,7,10-四氮杂环十二烷(L1)形成的[ML1]+的稳定性 log(K/dm3 mol-1)随 M+ 的变化依次为 Li+(8.07 ± 0.05 和 8.90 ± 0.05)、Na+(6.66 ± 0.05 和 7.49 ± 0.05)、K+(3.40 ± 0.05 和 5.在 298.2 K 和 I= 0.05 mol dm-3(NEt4ClO4)条件下,通过电位滴定法分别测定了乙腈和碳酸丙烯酯中的 Rb+(3.00 ± 0.05 和 4.23 ± 0.05)、Cs+(2.90 ± 0.05 和 4.04 ± 0.05)和 Ag+(9.35 ± 0.04 和 14.00 ± 0.05)。母大环 1,4,7,10-四氮杂环十二烷(L2)的络合物稳定性较差。对于 [NaL1]+ 在乙腈和碳酸丙烯酯中的单分子解络合,kd(298.2 K)= 78.5 ± 1.0 和 26.1 ± 0.6 s-1,ΔHd‡= 49.2 ± 0.3 和 57.7 ± 0.4 kJ mol-1,以及 ΔSd‡=-43.7 ± 0.9 和 -24.0 ± 1.0 J K-1 mol-1。碳-13 NMR 光谱显示,在甲醇中方对映[LiL1]+、[NaL1]+ 和[KL1]+ 的对映体化过程中,ke(298.2 K)= 18 300 ± 3100、7100 ± 220 和 7010 ± 200 s-1,ΔHe‡= 41.3 ± 1.3、24.6 ± 0.5 和 53.7 ± 0.6 kJ mol-1,以及 ΔSe‡=-24.8 ± 5.9、-88.6 ± 1.8 和 8.8 ± 2.3 J K-1 mol-1。[LiL1]+和[NaL1]+的对映体化要比 L1 的分子间交换快得多,但[KL1]+的对映体化主要是通过 L1 的分子间交换进行的。