Targeting Molecular Magnetic Hysteresis at Liquid Nitrogen Temperatures

50多年来，经济因素推动了电子设备小型化的稳定趋势。然而，农业化的进展速度已经开始停滞，据预测，十年内可能会达到一个稳定期。因此，寻求“自下而上”的替代办法，以与目前的“自上而下”的办法相抗衡，确保技术的持续进步。高密度数据存储的一个有前途的解决方案是使用单分子磁体（SMM）。这些分子可以存储磁信息，因此可以提供尽可能小的器件。镧系元素（Ln）SMM由于其良好的磁性而成为主要候选者，但目前这些SMM只能在昂贵的液氦冷却下工作。Ln SMM保留磁性信息的最高温度取决于Ln的选择、与Ln键合的原子和所得分子几何形状以及磁弛豫途径的竞争。这些因素都可能被控制，但目前的松弛机制仍然知之甚少。有效的弛豫过程可以显着降低磁信息被保留的温度，基于仅从考虑孤立的Ln SMM所预测的，因此必须对这些进行研究以取得进展。我们最近发现，Ln阳离子仅键合到轴向排列的两个五元碳原子环上给出了SMM，已经观察到对于数据存储至关重要的记忆效应。因此，我们的目标是基于此基序合成更复杂的Ln SMM结构，以提供更高的滞后温度。这些系统可以在液氮温度以上运行，在这一点上，它们将成为技术上可行的。这些系统的磁弛豫路径可以在很大的温度范围内进行深入研究。这将使我们能够加深对弛豫机制的影响因素的理解，以便将来我们能够设计出不利于这种过程的Ln SMM，并且可以在更高的温度下存储磁信息。在最近的工作中（Nature，2017，548，439），我们使用我们的Ln SMM设计标准报告了迄今为止报道的最大分子滞后温度（60 K）。这是近25年来最大的一次飞跃（之前的纪录，14 K，是在2011年创造的; 4 K是1993年的初步成就），现在距离在经济上可行的液氮制度下运行只有17 K。我们已经对该系统的设计进行了理论预测，以通过修改碳原子环来进一步提高滞后温度，并在本提案中列出了实现这一目标的合成路线。更雄心勃勃的是，我们的目标是合成“三层德克尔”化合物，其中含有两个镝阳离子和三个小的碳原子环，呈近似圆柱形排列。Ln离子更喜欢高的配位数，因此，只含有五元碳原子环的三重德克尔配合物的合成将是一个了不起的合成成就。这将提供必要的信息，以指导我们的开创性研究磁弛豫途径及其关系的几何形状和电子结构的Ln SMM。理想地，我们可以合成可以在液氮温度下操作的Ln SMM。

For over fifty years economic factors have driven a steady trend of making electronic devices smaller. However, the rate of progress in miniaturisation has started to stall, and it has been predicted that a plateau may be reached within ten years. As such, "bottom-up" alternatives are sought to rival the current "top-down" approach to ensure continued technological advancement. One promising solution for high-density data storage is to use Single Molecule Magnets (SMMs). These are molecules that can store magnetic information, and could therefore give the smallest possible devices.Lanthanide (Ln) SMMs have emerged as leading candidates due to their favourable magnetic properties, but at present these only function with expensive liquid helium cooling. The highest temperature at which Ln SMMs retain magnetic information is dictated by the choice of Ln, the atoms bonded to the Ln and the resultant molecular geometry, and the competition of magnetic relaxation pathways. These factors can all potentially be controlled but at present the relaxation mechanisms are still poorly understood. Efficient relaxation processes can significantly lower the temperature at which magnetic information is retained, based on what would be predicted solely from consideration of an isolated Ln SMM, and thus these must be investigated to make progress.We have recently found that Ln cations bonded only to two five-membered carbon atom rings in an axial arrangement give a SMM for which the highest temperatures at which magnetic hysteresis, a memory effect that is essential for data storage, has ever been observed. As such, we target the syntheses of more complex Ln SMM structures based upon this motif to provide even higher hysteresis temperatures. These systems could operate above liquid nitrogen temperatures, at which point they would become technologically viable. The magnetic relaxation pathways of these systems can be studied in depth over a large temperature range. This will allow us to deepen our understanding of the factors governing relaxation mechanisms, so that in future we can design Ln SMMs that disfavour such processes and can store magnetic information at even higher temperatures.In recent work (Nature, 2017, 548, 439), we have used our Ln SMM design criteria to report by far the largest molecular hysteresis temperature reported to date (60 K). This is the single biggest leap in nearly 25 years (the previous record, 14 K, was set in 2011; 4 K was the initial achievement in 1993) and is now only 17 K away from operation under an economically viable liquid nitrogen regime. We have made theoretical predictions for improvements to the design of this system to raise the hysteresis temperature even further by modifying the carbon atom rings, and have set out synthetic routes to achieve this goal in this proposal. More ambitiously, we target the synthesis of "triple decker" compounds that contain two dysprosium cations and three small carbon atom rings in an approximately cylindrical arrangement. Ln ions prefer high coordination numbers, hence the synthesis of triple decker complexes containing only five-membered carbon atom rings would be a remarkable synthetic achievement.All synthetic studies in this proposal will be complemented by high level physical analysis of magnetic and electronic properties, including computational modelling. This will provide essential information to guide our pioneering studies of magnetic relaxation pathways and their relationship to the geometry and electronic structure of Ln SMMs. Ideally we may synthesise a Ln SMM that can operate at liquid nitrogen temperatures.