The Acid-Base Through-the-Cage Interaction as an Example of an Inversion in a Cage Isomerism

Symmetry

Sławomir Ostrowski¹  JanC. Dobrowolski¹ 

[1] Institute of Nuclear Chemistry and Technology, 16 Dorodna Street, 03-195 Warsaw, Poland;

关键词: endohedral fullerenes;    isomerism;    acid-base interaction;   

DOI  :  10.3390/sym12081291

来源: DOAJ

【 摘 要 】

We define a new inversion in a cage isomerism (ic): X@C∙∙∙Y ₪_ic Y@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.

【 授权许可】

Unknown