Inclusion complexation of tetraalkylphosphonium salts (PSs) with cucurbit[7]uril (CB[7]) was studied spectrophotometrically using methylene blue as a chemical indicator. Differences in the inclusion behaviour caused by the central ions in PSs and tetraalkylammonium salts (ASs) are described herein. The inclusion complexation constant (K) of PS3 with a C3-alkyl chain is remarkably smaller than those of the other PSs, indicating that PS3 is most suitable for clathrate-hydrate formation in bulk solution. In the AS inclusions, AS4 with a C4-alkyl chain showed the small K value. Furthermore, the K values of PSs with CB[7] were measured under high pressure. The K values of CB[7] increased with increasing external pressure and decreasing solvent polarity. From the high-pressure results, the volume change (ΔVrepel) caused by water molecules released from the CB[7] cavity was evaluated. A volumetric study for the inclusion of PSs with CB[7] indicated that in PS6 and PS8 with long C6 and C8 chains, respectively, one alkyl chain was encapsulated in the CB[7] cavity. In the other PSs with short chains, two alkyl chains could be accommodated in the cavity. Based on the effects of temperature, substituents, and external pressure, differences in the inclusion mechanisms of PSs and ASs for CB[7] are discussed.

中文翻译：

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四烷基鏻和铵盐与葫芦[7]脲包合物的对比研究

使用亚甲蓝作为化学指示剂，通过分光光度法研究了四烷基鏻盐 (PS) 与葫芦 [7] 脲 (CB[7]) 的包合络合。本文描述了由 PSs 和四烷基铵盐 (ASs) 中的中心离子引起的夹杂行为的差异。具有C3-烷基链的PS3 的包合常数（K）明显小于其他PS，表明PS3 最适合在本体溶液中形成包合物-水合物。在 AS 夹杂物中，具有 C4-烷基链的 AS4 显示出较小的 K 值。此外，在高压下测量了含 CB[7] 的 PS 的 K 值。CB[7] 的 K 值随着外部压力的增加和溶剂极性的降低而增加。从高压结果来看，评估了由 CB[7] 腔释放的水分子引起的体积变化 (ΔVrepel)。对包含 CB[7] 的 PS 的体积研究表明，在分别具有长 C6 和 C8 链的 PS6 和 PS8 中，一个烷基链被封装在 CB[7] 腔中。在其他具有短链的 PS 中，空腔中可以容纳两个烷基链。基于温度、取代基和外部压力的影响，讨论了 PSs 和 ASs 对 CB [7] 的包合机制的差异。