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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Noncovalent binding between fullerenes and protonated porphyrins in the gas phase
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Noncovalent binding between fullerenes and protonated porphyrins in the gas phase

机译：富勒烯与质子化卟啉在气相中的非共价结合

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摘要

Noncovalent interactions between protonated porphyrin and fullerenes (C_(60) and C_(70)) were studied with five different meso-substituted porphyrins in the gas phase. The protonated porphyrin-fullerene complexes were generated by electrospray ionization of the porphyrin-fullerene mixture in 3:1 dichloromethane/methanol containing formic acid. All singly protonated porphyrins formed the 1:1 complexes, whereas porphyrins doubly protonated on the porphine center yielded no complexes. The complex ion was mass-selected and then characterized by collision-induced dissociation with Xe. Collisional activation exclusively led to a loss of neutral fullerene, indicating noncovalent binding of fullerene to protonated porphyrin. In addition, the dissociation yield was measured as a function of collision energy, and the energy inducing 50% dissociation was determined as a measure of binding energy. Experimental results show that C_(70) binds to the protonated porphyrins more strongly than C_(60), and electron-donating substituents at the meso positions increase the fullerene binding energy, whereas electron-withdrawing substituents decrease it. To gain insight into π-π interactions between protonated porphyrin and fullerene, we calculated the proton affinity and HOMO and LUMO energies of porphyrin using Hartree-Fock and configuration interaction singles theory and obtained the binding energy of the protonated porphyrin-fullerene complex using density functional theory. Theory suggests that the protonated porphyrin-fullerene complex is stabilized by π-π interactions where the protonated porphyrin accepts π-electrons from fullerene, and porphyrins carrying bulky substituents prefer the end-on binding of C_(70) due to the steric hindrance, whereas those carrying less-bulky substituents favor the side-on binding of C_(70).
机译：用五种不同的内消旋卟啉在气相中研究了质子化卟啉与富勒烯（C_（60）和C_（70））之间的非共价相互作用。质子化的卟啉-富勒烯配合物是通过在3：1的二氯甲烷/甲醇中将甲酸进行电喷雾电离而生成的。所有单质子化的卟啉均形成1：1的配合物，而在卟啉中心双加倍质子化的卟啉则不产生任何配合物。对复合离子进行了质量选择，然后通过碰撞诱导与Xe的离解进行了表征。碰撞激活仅导致中性富勒烯的损失，表明富勒烯与质子化卟啉的非共价结合。另外，测量离解产率作为碰撞能量的函数，并且将引起50％解离的能量确定为结合能的量度。实验结果表明，C_（70）与质子化的卟啉的结合比C_（60）更牢固，内消旋位置的供电子取代基增加了富勒烯的结合能，而吸电子取代基降低了富勒烯的结合能。为了深入了解质子化卟啉与富勒烯之间的π-π相互作用，我们使用Hartree-Fock和构型相互作用单论计算了卟啉的质子亲和力以及HOMO和LUMO能，并使用密度泛函获得质子化的卟啉-富勒烯复合物的结合能理论。理论表明质子化的卟啉-富勒烯复合物通过π-π相互作用得以稳定，其中质子化的卟啉接受来自富勒烯的π电子，而带有大取代基的卟啉由于空间位阻而倾向于C_（70）的末端键合，而带有较小体积取代基的化合物有利于C_（70）的侧面结合。

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