Magnetic Resonance of Dihydrogen Endofullerenes

富勒烯是由碳原子组成的足球形状的笼子，英国科学家哈里·克罗托因这一发现于1996年获得诺贝尔奖。笼子里是一片空地。化学家和物理学家已经发现了许多巧妙的方法来将原子或分子困在微小的富勒烯笼子里。这些被包裹的化合物被称为内富勒烯。最引人注目的方法之一是由日本科学家小松和村田开创的，他们是当前提案的项目合作伙伴。他们进行了分子手术。首先，通过一系列化学反应在富勒烯笼子上开一个洞。然后通过高温和高压将一个小分子如二氢(H2)插入到每个富勒烯笼子中。最后，进一步的一系列化学反应被用来再次缝合这些洞。结果产生了一种引人注目的化合物，名为二氢内富勒烯。甚至不得不发明一种新的符号来写下这个公式。将H2包裹在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，可以对其进行分析，以获得有关样品中分子、它们位于何处以及它们如何运动的详细信息。磁共振最常见的形式是磁共振成像(MRI)，它被用于医院获取解剖图像和诊断医疗条件。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性质，如水溶性。我们将研究H2分子在纳米笼子中的运动。在其中一个子项目中，我们将合成和结晶H2@C60分子，使它们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会表现出不寻常的行为。分子本身将发出磁共振信号，而不仅仅是原子核。我们将首次在固体材料上观察到这一现象。第二个子项目涉及一种称为邻位/对位转换的现象。Werner Heisenberg因预测普通氢有两种不同的形式，称为邻氢和仲氢而于1932年获得诺贝尔奖。事实证明，这是正确的。因此，H2@C60有两种不同的形式，一种含有邻氢，另一种含有仲氢。我们将在现场研究这两种形式是如何相互转化的，特别是光是否可以诱导邻位/对位转化。如果如预期的那样观察到影响，可能会产生一些重要的后果。特别是，通过用合适的激光束照射样品，应该可以将某些核磁共振信号的强度提高一大倍(高达近100万)。如果这项研究奏效，它将对广泛的科学产生影响，可能包括医学核磁共振。该项目的目的之一是进行初步工作，以确定这一新的核磁共振增强方案的可行性。

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.