Synthesis and Assembly of New Molecular Hosts: Solvation and the Energetics of Encapsulation
摘要:
Experimental details are given for the preparation of ''softballs'', large self-complementary molecules capable of assembly into pseudo-spherical capsules. Evidence is presented for their existence as hydrogen bonded dimers:in organic solvents, and binding affinities for the reversible encapsulation of smaller molecules of suitable size and shape are given. Studies at various temperatures result in calculated enthalpies and entropies of encapsulation that are positive; accordingly, the process is entropy driven. It is proposed that the hosts in their resting states contain two molecules of solvent such as benzene, and the encapsulation of a single large guest-the hostage-liberates the two solvents. The resulting increase in the number of free molecules gives rise to the increase in entropy observed for the exchange process. Experiments involving solvent mixtures are consistent with this rationale. Calculation of the capsule's interior volume and molecular dynamics simulations support the experimental observations, and hint at unexpected phenomena dealing with the occupancy factors of these systems.
Chiral Capsules. 1. Softballs with Asymmetric Surfaces Bind Camphor Derivatives
作者:Yuji Tokunaga、Julius Rebek
DOI:10.1021/ja972885t
日期:1998.1.1
Self-assembling “softballs” are hollow pseudospherical dimers held together by hydrogen bonds in organic solvents. They encapsulate smaller molecules of suitable size and shape. Stereochemical aspects of these systems are explored through the encapsulation of camphor derivatives. Both symmetrical softballs and those rendered chiral by functional groups on the softball's surface are examined by 1H NMR
自组装“垒球”是在有机溶剂中通过氢键结合在一起的空心假球形二聚体。它们封装了合适大小和形状的较小分子。这些系统的立体化学方面通过樟脑衍生物的封装进行了探索。对称垒球和由垒球表面的官能团呈现手性的垒球均通过 1 H NMR 方法进行检测。