Hosseini Ali, Taylor Steven, Accorsi Gianluca, Armaroli Nicola, Reed Christopher A, Boyd Peter D W
Department of Chemistry, The University of Auckland, Auckland, New Zealand.
J Am Chem Soc. 2006 Dec 13;128(49):15903-13. doi: 10.1021/ja066031x.
A calix[4]arene scaffolding has been used to construct bisporphyrin ("jaws" porphyrin) hosts for supramolecular binding of fullerene guests. Fullerene affinities were optimized by varying the nature of the covalent linkage of the porphyrins to the calixarenes. Binding constants for C60 and C70 in toluene were explored as a function of substituents at the periphery of the porphyrin, and 3,5-di-tert-butylphenyl groups gave rise to the highest fullerene affinities (26,000 M(-1) for C60). The origin of this high fullerene affinity has been traced to differential solvation effects rather than to electronic effects. Studies of binding constants as a function of solvent (toluene < benzonitrile < dichloromethane < cyclohexane) correlate inversely with fullerene solubility, indicating that desolvation of the fullerene is a major factor determining the magnitude of binding constants. The energetics of fullerene binding have been determined in terms of DelatH and DeltaS and are consistent with an enthalpy-driven, solvation-dependent process. A direct relationship between supramolecular binding of a fullerene guest to a bisporphyrin host and the appearance of a broad NIR absorption band have been established. The energy of this band moves in a predictable manner as a function of the electronic structure of the porphyrin, thereby establishing its origin in porphyrin-to-fullerene charge transfer.
杯[4]芳烃骨架已被用于构建双卟啉（“钳口”卟啉）主体，用于超分子结合富勒烯客体。通过改变卟啉与杯芳烃的共价连接性质，优化了富勒烯亲和力。研究了甲苯中C60和C70的结合常数与卟啉外围取代基的关系，3,5-二叔丁基苯基产生了最高的富勒烯亲和力（C60为26,000 M(-1)）。这种高富勒烯亲和力的起源已追溯到不同的溶剂化效应而非电子效应。结合常数与溶剂（甲苯<苄腈<二氯甲烷<环己烷）的函数关系研究表明，其与富勒烯溶解度呈反比，这表明富勒烯的去溶剂化是决定结合常数大小的主要因素。已根据ΔH和ΔS确定了富勒烯结合的能量学，其与焓驱动、溶剂化依赖性过程一致。已建立了富勒烯客体与双卟啉主体的超分子结合与宽近红外吸收带出现之间的直接关系。该吸收带的能量随卟啉电子结构的变化以可预测的方式移动，从而确定其起源于卟啉到富勒烯的电荷转移。
