Physical basis of self-assembly macrocyclizations
Physical basis of self-assembly macrocyclizations
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DOI：
10.1021/jp9816723
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发表时间：
1998-07-16
影响因子：
3.3
通讯作者：
Ercolani, G
中科院分区：
文献类型：
--
作者：
Ercolani, G
自组装大环化反应发生在热力学控制下的理论处理。的基本量的治疗是基于自组装的环状n-聚体（EMn）的有效摩尔浓度和单官能反应物（K-间）之间的分子间模型反应的平衡常数。这些量的知识允许的自组装大环的分布曲线的评价。为了进行有效的自组装，需要两个条件：（i）自组装大环必须具有比其他环状低聚物大得多的EM;（ii）产物EMnKinter必须不低于185 r，其中r是将环状低聚物中的单体单元保持在一起的键的数目，越高越好。它表明，在一个无限大的K-内值的限制，有一个临界单体浓度（cme = nEM（n）），低于该系统几乎是由自组装大环的浓度，后者保持恒定和过量的单体产生无环物种。一般来说，自组装的最佳单体浓度略高于cmc的十分之一。EMnKinter的值越高，偏离该值的重要性越小;然而，初始单体的浓度不应超出由较低的自组装浓度和cmc限定的范围。Hunter等人得出的关于自组装大环化的先前结论（J. Chem. Sec.，化学通信1995年，2563）是批评在目前的做法。
A theoretical treatment of self-assembly macrocyclizations occurring under thermodynamic control is presented. The fundamental quantities on which the treatment is based are the effective molarity of the self-assembling cyclic n-mer (EMn) and the equilibrium constant for the intermolecular model reaction between monofunctional reactants (K-inter). Knowledge of these quantities allows the evaluation of the distribution curve of the self-assembling macrocycle. In order for effective self-assembly to take place two conditions are required: (i) the self-assembling macrocycle must have an EM much larger than that of the other cyclic oligomers; (ii) the product EMnKinter must be not lower than 185r, where r is the number of bonds that hold together the monomer units in the cyclic oligomer, the higher the better. It is shown that in the limit of an infinite value of K-inter there is a critical monomer concentration (cme = nEM(n)) below which the system is virtually composed of the self-assembling macrocycle only and above which the concentration of the latter remains constant and the excess monomer produces acyclic species only. In general the optimum monomer concentration for self-assembly is slightly more than one-tenth of the cmc. Deviation from this value is less and less important the higher the value of EMnKinter; however, the concentration of the initial monomer should not be outside the range defined by the lower self-assembly concentration and the cmc. Previous conclusions about self-assembly macrocyclizations drawn by Hunter et al. (J. Chem. Sec., Chem. Commun. 1995, 2563) are criticized in the light of the present approach.