Selective Anion Encapsulation by a Metalated Cryptophane with a π-Acidic Interior

Metalation of the exterior arene faces of the molecular capsule (±)-cryptophane-E with [Cp*Ru]+ moieties results in a π-acidic cavity capable of encapsulating anions. The [CF3SO3]- and [SbF6]- salts have been crystallographically characterized and demonstrate the encapsulation of these anions by the metalated cryptophane. 1H and 19F NMR spectroscopy establish the binding of anions in NO2CD3 solution and reveal the relative affinity of the cavity for different anions (KX−/KOTf−):  [BF4]- ≈ 0, [PF6]- = 1.18, [CF3SO3]- ≡ 1, [SbF6]- = 0.30. Variable temperature rate studies reveal the activation barrier for triflate encapsulation to be ΔG⧧298K = 18.0(8) kcal·mol-1 (ΔH⧧ = 17.5(4) kcal·mol-1 and ΔS⧧ = 2(1) cal·mol-1·K-1).

将分子胶囊(molecular capsule)(±)-穴番-E [(±)-cryptophane-E]的外侧芳烃面与(五甲基环戊二烯基)合钌阳离子([Cp*Ru]+)进行金属化修饰，可获得具备π酸性的空腔，该空腔可实现阴离子的包埋。三氟甲磺酸根([CF3SO3]-)与六氟锑酸根([SbF6]-)的盐类已通过晶体学方法完成表征，证实了金属化穴番对上述阴离子的包埋作用。氢谱(1H NMR)与氟谱(19F NMR)波谱分析证实了阴离子在氘代硝基甲烷(NO2CD3)溶液中的结合行为，并揭示了该空腔对不同阴离子的相对结合亲和力（以KX−/KOTf−计）：[BF4]- ≈ 0，[PF6]- = 1.18，[CF3SO3]- ≡ 1，[SbF6]- = 0.30。变温速率研究结果显示，三氟甲磺酸根包埋过程的活化能垒为ΔG⧧298K = 18.0(8) kcal·mol-1（对应ΔH⧧ = 17.5(4) kcal·mol-1，ΔS⧧ = 2(1) cal·mol-1·K-1）。