Bio-Nanotechnology Center, Department of Chemistry, Pohang University of Science and Technology, San31 Hyoja-dong Nam-gu, Pohang, Kyungbuk 790-784, Korea.
Phys Chem Chem Phys. 2011 Dec 7;13(45):20248-54. doi: 10.1039/c1cp22091h. Epub 2011 Oct 12.
Noncovalent binding of fullerenes to bisporphyrins was studied in the gas phase by energy-dependent collision-induced dissociation (CID) with Xe under single-collision conditions. The electrospray ionization mass spectra of calix[4]arene-linked bisporphyrins show that bisporphyrins take up to 3-4 protons, depending on the type of meso-substituents. Of the protonated bisporphyrins, the diprotonated species form stable 1:1 complexes with fullerenes (C(60) and C(70)). CID cracking patterns of the diprotonated bisporphyrins indicate that each monomeric porphyrin moiety is singly protonated. CID yield-energy curves obtained from the 1:1 diprotonated bisporphyrin-fullerene complexes suggest that a fullerene occupies the endo-binding site intercalated between the two singly protonated porphyrin moieties. In the cases of 1:2 diprotonated bisporphyrin-fullerene complexes, CID results show that one fullerene binds inside (endo-binding) and the other outside (exo-binding). The exo-binding mode is energetically almost identical to the binding of fullerenes to singly protonated porphyrin monomers. The endo-binding energy is at least twice the exo-binding energy. To gain insights into the binding mode, we optimized structures of diprotonated bisporphyrins and their 1:1 endo-complexes with fullerenes, and calculated the endo-binding energy for C(60), C(70) (end-on), and C(70) (side-on). The endo-binding of fullerenes to diprotonated bisporphyrins nearly doubles the π-π interactions while reducing the electrostatic repulsion between the two singly protonated porphyrin moieties. The side-on binding of C(70) is favored over the end-on binding because the former exerts less steric strain to the lower rim of calixarene.
通过在单分子碰撞条件下使用氙气进行能量依赖性碰撞诱导解离（CID），在气相中研究了富勒烯与双卟啉的非共价键合。杯[4]芳烃连接的双卟啉的电喷雾电离质谱表明，双卟啉可接受多达 3-4 个质子，具体取决于meso-取代基的类型。在质子化的双卟啉中，二价质子化物种与富勒烯（C(60)和 C(70)）形成稳定的 1:1 配合物。二价质子化双卟啉的 CID 裂解模式表明，每个单体卟啉部分都被单质子化。从 1:1 二价质子化双卟啉-富勒烯配合物获得的 CID 产率-能量曲线表明，一个富勒烯占据了夹在两个单质子化卟啉部分之间的内结合位。在 1:2 二价质子化双卟啉-富勒烯配合物的情况下，CID 结果表明，一个富勒烯在内（内结合）结合，另一个在外（外结合）结合。外结合模式在能量上几乎与富勒烯与单质子化卟啉单体的结合相同。内结合能至少是外结合能的两倍。为了深入了解结合模式，我们优化了二价质子化双卟啉及其与富勒烯的 1:1 内配合物的结构，并计算了 C(60)、C(70)（端对端）和 C(70)（侧对侧）的内结合能。富勒烯与二价质子化双卟啉的内结合使 π-π 相互作用增加了近一倍，同时减少了两个单质子化卟啉部分之间的静电排斥。C(70)的侧对侧结合比端对端结合更有利，因为前者对内酰胺环的下边缘施加的空间应变较小。
