Magnetic Resonance of Dihydrogen Endofullerenes

富勒烯是由碳原子组成的足球状笼子，英国科学家哈里·克罗托因发现富勒烯而获得1996年诺贝尔奖。笼子里是一个空的空间。化学家和物理学家已经发现了许多巧妙的方法将原子或分子捕获在微小的富勒烯笼中。这些包封的化合物被称为内富勒烯。其中最引人注目的方法是由日本科学家小松和村田率先提出的，他们是目前提案的项目合作伙伴。他们做了分子手术。首先，使用一系列化学反应在富勒烯笼中打开一个洞。然后通过使用高温和高压将诸如二氢（H2）的小分子插入每个富勒烯笼中。最后，又进行了一系列的化学反应，把洞缝起来。其结果是一种名为二氢富勒烯的化合物。甚至必须发明一种新的符号来写下公式。将H2包封在C60富勒烯分子中的结果表示为H2@C60。在这个项目中，我们将对H2@C60的衍生物进行磁共振实验。磁共振是一种将样品置于强磁场中并用无线电波照射的方法。氢原子的原子核产生无线电波响应，可以分析该无线电波响应以获得关于样品中的分子的详细信息，它们位于何处以及它们如何移动。最常见的磁共振形式是磁共振成像（MRI），它在医院中用于获得解剖图片和诊断医疗状况。在这个项目中，我们将对H2@C60化合物及其高度对称的取代衍生物进行磁共振，这些化合物具有许多有用的特性，如水溶性。我们将研究H2分子在纳米级笼中的运动。在其中一个子项目中，我们将合成和结晶H2@C60分子，使其保持在高度对称的晶体中。根据某些理论，氢分子在这些条件下将以不寻常的方式运动。分子本身会发出磁共振信号，而不仅仅是原子核。我们将尝试在固体材料上首次观察到这种现象。第二个子项目涉及一种称为邻位/帕拉转换的现象。维尔纳·海森堡于1932年获得诺贝尔奖，因为他预测普通氢有两种不同的形式，称为正氢和仲氢。这被证明是正确的。因此，H2@C60形式有两种不同的类型，一些含有邻位氢，一些含有仲氢。我们将在原位研究这两种形式是如何相互转化的，特别是，邻位/帕拉转化是否可以被光诱导。如果观察到预期的效果，一些重要的后果可能会随之而来。特别地，通过用合适的激光束照射样品，可以将某些NMR信号的强度提高很大一部分（高达几乎100万）。如果这项研究成功，它将对广泛的科学产生影响，可能包括医学MRI。该项目的目的之一是进行初步工作，这将确定这种新的NMR增强方案的可行性。

Fullerenes are football-shaped cages of carbon atoms, for the discovery of which the British scientist Harry Kroto won the Nobel prize in 1996. Inside the cage is an empty space. Chemists and physicists have found many ingenious ways of trapping atoms or molecules inside the tiny fullerene cages. These encapsulated compounds are called endofullerenes. One of the most remarkable methods was pioneered by the Japanese scientists Komatsu and Murata, who are project partners in the current proposal. They performed molecular surgery . First, a series of chemical reactions was used to open a hole in the fullerene cages. A small molecule such as dihydrogen (H2) was then inserted into each fullerene cage by using high temperature and pressure. Finally, a further series of chemical reactions was used to sew the holes back up again. The result was the remarkable chemical compound called dihydrogen endofullerene. A new notation even had to be invented to write the formula down. The result of encapsulating H2 in a C60 fullerene molecule is denoted H2@C60. In this project we will perform magnetic resonance experiments on derivatives of H2@C60. Magnetic resonance is a method in which a sample is placed in a strong magnetic field and illuminated with radiowaves. The nuclei of the hydrogen atoms produce a radiowave response that may be analyzed to obtain detailed information about the molecules in the sample, where they are located, and how they are moving. The most familiar form of magnetic resonance is magnetic resonance imaging (MRI) which is used in hospitals to obtain anatomical pictures and diagnose medical conditions.In this project we will perform magnetic resonance on H2@C60 compounds and their highly-symmetric substituted derivatives, which have a number of useful properties such as water solubility. We will study the motion of the H2 molecules inside the nanoscale cages.In one of the subprojects we will synthesize and crystallize H2@C60 molecules in such a way that they are held in a highly symmetrical crystal. According to certain theories, the hydrogen molecules will behave in an unusual way under these conditions. The molecules themselves will emit magnetic resonance signals, not just the nuclei. We will try to observe this phenomenon for the first time on solid materials.The second subproject concerns a phenomenon called ortho/para conversion. Werner Heisenberg received the Nobel Prize in 1932 for predicting that ordinary hydrogen has two distinct forms, called ortho and parahydrogen. This was proved to be correct. The H2@C60 forms therefore come in two different types, some containing ortho hydrogen, and some containing parahydrogen. We will study in situ how these two forms interconvert with each other, and in particular, whether the ortho/para conversion may be induced by light.If the effects are observed as expected, some important consequences may follow. In particular, it should become possible to enhance the strength of certain NMR signals by a large factor (up to of almost 1 million) by irradiating the sample with a suitable laser beam. If this works it will have implications for a wide range of sciences, possibly including medical MRI. One of the aims of this project is to perform the preliminary work which will determine the feasibility of this novel NMR enhancement scheme.