Cyclopropane as an Unsaturation “Effect Isostere”: Lowering the Melting Points in Lipid-like Ionic Liquids
Cyclopropane as an Unsaturation “Effect Isostere”: Lowering the Melting Points in Lipid-like Ionic Liquids
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环丙烷作为不饱和度“等排效应”：降低类脂离子液体的熔点
DOI：
10.1021/acs.jpcb.2c07872
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Mirjafari, Arsalan
中科院分区：
文献类型：
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作者：
O’Brien, Richard A.;Hillesheim, Patrick C.;Soltani, Mohammad;Badilla-Nunez, Kelly J.;Siu, Ben;Musozoda, Muhammadiqboli;West, Kevin N.;Davis, James H.;Mirjafari, Arsalan
用环丙烷基序取代不饱和键作为（生物）电子等排体是细菌中一种广泛的策略，用于调节脂质双层的流动性并在暴露于不利环境条件（例如高温、低pH等）时保护膜。受这种现象的启发，我们在此讨论了环丙烷化（顺式和反式构型）对熔化的相对影响 通过热物理分析、X 射线晶体学和计算建模的结合，研究了一系列类脂离子液体的点、堆积效率和顺序。数据表明，在设计具有低熔点的高亲脂性离子液体时，可能存在相当大的结构自由度。虽然类脂离子液体的环丙烷化比其烯烃类似物更能抵抗需氧降解，但对熔点降低的影响并不那么明显。我们的结果表明，相对于带有线性、饱和或硫醚侧链的对应物，在咪唑鎓基离子液体的长脂肪链中掺入一个或多个环丙基部分对于降低此类材料的熔点非常有效。结果表明，环丙烷部分有效地破坏了堆积，有利于侧链中形成稀疏构象，从而提高了流动性。这与亚甲基桥的构型无关，尽管观察到顺式和反式单环丙烷化离子液体对熔点的影响存在显着差异。
The replacement of unsaturation with a cyclopropane motif as a (bio)isostere is a widespread strategy in bacteria to tune the fluidity of lipid bilayers and protect membranes when exposed to adverse environmental conditions, e.g., high temperature, low pH, etc. Inspired by this phenomenon, we herein address the relative effect of the cyclopropanation, bothcisandtransconfigurations, on melting points, packing efficiency, and order of a series of lipid-like ionic liquids via a combination of thermophysical analysis, X-ray crystallography, and computational modeling. The data indicate there is considerable structural latitude possible when designing highly lipophilic ionic liquids that exhibit low melting points. While cyclopropanation of the lipid-like ionic liquids provides more resistance to aerobic degradation than their olefin analogs, the impact on the melting point decrease is not as pronounced. Our results demonstrate that incorporating one or more cyclopropyl moieties in long aliphatic chains of imidazolium-based ionic liquids is highly effective in lowering the melting points of such materials relative to their counterparts bearing linear, saturated, or thioether side chains. It is shown that the cyclopropane moiety effectively disrupts packing, favoring formation ofgaucheconformer in the side chains, resulting in enhancement of fluidity. This was irrespective of the configuration of the methylene bridge, although marked differences in the effect ofcis- andtrans-monocyclopropanated ILs on the melting points were observed.