DataSheet1_Solid-State and Theoretical Investigations of Some Banister-Type Macrocycles with 2,2’-Aldoxime-1,1’-Biphenyl Units.pdf

In the context of helical chirality, bridging of biphenyl units leads to banister-type compounds and the stability of the resulted atropisomers may increase dramatically if suitable changes are performed in the linker unit that coils around the biphenyl moiety. A rigorous density functional theory (DFT) study was conducted for macrocycles containing rigid oxime ether segments connected to the biphenyl backbone in order to determine how the rotation barriers are influenced by the presence of either a flexible oligoethyleneoxide or a more rigid m–xylylene component in the macrocycle. The calculated values for the racemization barrier were in good agreement with those obtained experimentally and confirm the benefit of introducing a more rigid unit in the macrocycle on the stability of atropisomers. Solid-state data were obtained and computed data were used to assess the contribution brought by supramolecular associations observed in the lattice to the stabilization of the crystal structure. Beside introducing rigidity in the linker, complexation of flexible macrocycles with alkali metal ions is also contributing to the stability of atropisomers, leading to values for the racemization barrier matching that of the rigid macrocycle. Using diethylammonium cation as guest for the macrocycle, a spectacular increase in the barrier to rotation was observed for the resulted pseudo[2]rotaxane.

在螺旋手性领域，联苯单元的桥接形成banister型化合物，若对围绕联苯基团的连接单元进行适宜的改变，则所得的外消旋异构体的稳定性可能显著提升。为了探究在宏观环中存在柔性寡乙二醇氧或更刚性的m-乙基苯单元时，旋转势垒如何受到影响，本研究对包含刚性肟醚段并与联苯骨架相连的巨环进行了严格的密度泛函理论（DFT）研究。计算得到的消旋化势垒值与实验结果相符，并证实了在宏观环中引入更刚性单元对于外消旋异构体稳定性的益处。获得了固态数据，并利用计算数据评估了晶格中观察到的超分子相互作用对晶体结构稳定化的贡献。除了在连接单元引入刚性外，柔性宏观环与碱金属离子的络合也促进了外消旋异构体的稳定性，导致消旋化势垒值与刚性宏观环相匹配。以二乙基铵阳离子作为宏观环的客体，观察到旋转势垒的显著增加，形成了伪[2]轮烷。