We define a new inversion in a cage isomerism (ic): X@C⋯Y₪icY@C⋯X, (₪ is the isomerism relation) as an isomerism in the three-component system of molecules X, Y, and a cage C, in which one of the molecules is located inside and the other outside the cage. The ic isomerism is similar to the endo-exo one, which occurs only if either the interior or exterior of C is empty. By contrast, ic occurs only if neither the interior nor the exterior of C is empty. We also discuss the other closely related types of isomerisms are also discussed. Calculations of the XH⋯NH3@C60 and NH3⋯HX@C60ic isomers were performed at the ωB97XD/Def2TZVP level. The calculated energies demonstrated that the systems with the HX acid outside (X = F, Cl) and the NH3 base inside the cage, XH⋯NH3@C60, are more stable than their ic isomers, NH3⋯HX@C60, by about 4–8 kcal/mol. This is because NH3 is more stabilized inside the cage than HX (a matter of 6.5 kcal/mol). In the studied systems and subsystems, the HX molecules are Lewis acids and the NH3 molecule is always a Lewis base. The C60 molecule with HX inside or outside the cage is also an acid for the NH3 base positioned outside or inside the cage. On the other hand, the C60 cage is truly amphoteric because it is simultaneously an acid and a base.

中文翻译：

---

酸碱通过笼子相互作用作为笼子异构倒置的一个例子

我们在笼式异构（ic）中定义了一个新的反转：X@C⋯Y₪icY@C⋯X，（₪ 是异构关系）作为分子 X、Y 和笼的三组分系统中的异构C，其中一个分子位于笼内，另一个位于笼外。ic 异构与内-外异构相似，仅当 C 的内部或外部为空时才会发生。相比之下，只有当 C 的内部和外部都不为空时，ic 才会发生。我们还讨论了其他密切相关的异构体类型。XH⋯NH3@C60 和 NH3⋯HX@C60ic 异构体的计算在 ωB97XD/Def2TZVP 水平进行。计算的能量表明，外部有 HX 酸 (X = F, Cl) 和笼内有 NH3 碱的系统 XH⋯NH3@C60 比它们的 ic 异构体 NH3⋯HX@C60 稳定约 4 –8 大卡/摩尔。这是因为 NH3 在笼内比 HX 更稳定（大约 6.5 kcal/mol）。在研究的系统和子系统中，HX 分子是路易斯酸，NH3 分子总是路易斯碱。笼内或笼外带有 HX 的 C60 分子也是位于笼外或笼内的 NH3 碱的酸。另一方面，C60 笼确实是两性的，因为它同时是酸和碱。