The dissociation of hierarchically formed dimeric triple lithium bridged triscatecholate titanium(IV) helicates with hydrocarbyl esters as side groups is systematically investigated in DMSO. Primary alkyl, alkenyl, alkynyl as well as benzyl esters are studied in order to minimize steric effects close to the helicate core. The ¹H NMR dimerization constants for the monomer–dimer equilibrium show some solvent dependent influence of the side chains on the dimer stability. In the dimer, the ability of the hydrocarbyl ester groups to aggregate minimizes their contacts with the solvent molecules. Due to this, most solvophobic alkyl groups show the highest dimerization tendency followed by alkenyls, alkynyls and finally benzyls. Furthermore, trends within the different groups of compounds can be observed. For example, the dimer is destabilized by internal double or triple bonds due to π–π repulsion. A strong indication for solvent supported London dispersion interaction between the ester side groups is found by observation of an even/odd alternation of dimerization constants within the series of n‐alkyls, n‐Ω‐alkenyls or n‐Ω‐alkynyls. This corresponds to the interaction of the parent hydrocarbons, as documented by an even/odd melting point alternation.

中文翻译：

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揭示 DMSO 溶液中形成二聚钛 (IV) 三邻苯二酚酸酯时烃酯取代基的相互作用

在 DMSO 中系统地研究了以烃基酯为侧基的分层形成的二聚三锂桥三儿茶酚酸钛 (IV) 螺旋盐的解离。研究了伯烷基酯、烯基酯、炔基酯以及苄基酯，以尽量减少靠近螺旋核心的空间效应。^{单体-二聚体平衡的1} H NMR 二聚常数显示出侧链对二聚体稳定性的一些溶剂依赖性影响。在二聚体中，烃基酯基团聚集的能力最大限度地减少了它们与溶剂分子的接触。因此，大多数疏溶剂烷基表现出最高的二聚倾向，其次是烯基、炔基，最后是苄基。此外，可以观察到不同组化合物内的趋势。例如，由于 π-π 排斥，内部双键或三键使二聚体不稳定。通过观察n-烷基、n -Ω-烯基或n -Ω-炔基系列中二聚常数的偶数/奇数交替，发现了酯侧基之间溶剂支持的伦敦分散体相互作用的有力指示。这对应于母体碳氢化合物的相互作用，如偶数/奇数熔点交替所记录的那样。