Synthesis and Characterization of Transition Metal and Main Group Complexes with Unusual Bonding and Physical Properties

具有异常键合和物理性质的过渡金属和主族配合物的合成与表征

• 批准号: 1263760
• 负责人: Philip Power
• 金额: $ 55.7万
• 依托单位: University of California-Davis
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-15 至 2017-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1263760&HistoricalAwards=false
• 关键词: Synthesis; Characterization; Transition; Metal; Main

With the support of the Chemical Synthesis Program of the Chemistry Division, Professor Philip Power and his group at the Chemistry Department at the University of California-Davis will investigate the chemical and physical properties of low-coordinate transition and main group complexes stabilized by large ligands. This award will allow exploration of the synthesis of new examples of stable two-coordinate, open-shell transition metal species having d(1)-d(9) electron configurations. Several new types of ligands will be used to stabilize them making use of a combination of steric and dispersive forces. The new, linear complexes will have increased metal accessibility and high reactivity because of the low number of metal ligands. The linear coordination will also exert a powerful effect on their magnetic properties and their ability to exhibit single molecule magnetism (SMM). In essence, their linear geometry will maximize orbital contributions to the magnetic moment. This will have a large effect on the extent of zero-field splitting and hence the barriers to spin-reversal. The factors that affect the barrier to spin reversal (ligand, metal oxidation state etc.) will be investigated systematically to maximize it and induce SMM at room temperature. The transition metal work will be paralleled by work on low-oxidation state main group complexes with similar ligands. The primary objective is an understanding on how dispersion forces between the ligands affect the structures of the compounds by imposing specific geometries in both the main group and transition metal species. A magnetic molecule (i. e., a molecule containing unpaired electrons) can behave, in principle, like an ordinary bar magnet if the spins of the individual unpaired (miniature bar magnets) electrons are aligned and kept aligned in a specific direction. In practice such behavior is unknown at room temperature because the spins of the electrons can flip rapidly between opposite directions such that permanent magnetism is lost. The design of molecules that maximize the spin flip barrier sufficiently to enable the molecular magnets to maintain their alignment at room temperature is a formidable problem. Overcoming this difficulty will impact numerous physical phenomena that depend on electromagnetic effects. The proposed research will help to understand the factors that control the barrier by a systematic investigation of how the atoms or groups of atoms attached to the metal affect the barriers to spin flip. The research will also involve the training of several undergraduate, graduate and post-doctoral students in a wide spectrum of physico-chemical techniques. Students will acquire skills ranging from the synthesis of highly air and moisture sensitive compounds to conduction sophisticated investigations of magnetic properties. Students will also be exposed to national and international collaborations to broaden their experience and education.

在化学系化学合成计划的支持下，加州大学戴维斯分校化学系的菲利普·鲍尔教授和他的团队将研究大配体稳定的低配位过渡和主族配合物的化学和物理性质。该奖项将允许探索合成具有d(1)-d(9)电子组态的稳定的双配位、开壳层过渡金属物种的新实例。几种新型的配体将被用来稳定它们，利用空间和色散力的组合。由于金属配体的数量较少，新的线性络合物将增加金属的可及性和高反应性。这种线性配位也将对它们的磁性和展示单分子磁性(SMM)的能力产生很大的影响。本质上，它们的线性几何形状将使轨道对磁矩的贡献最大化。这将对零场分裂的程度产生很大影响，从而影响自旋反转的势垒。影响自旋反转势垒的因素(配体、金属氧化态等)将进行系统的研究，以最大限度地利用它，并在室温下诱导SMM。过渡金属的工作将与具有相似配体的低氧化态主族络合物的工作相平行。主要目标是了解配体之间的分散力如何通过在主族和过渡金属物种中施加特定的几何形状来影响化合物的结构。磁性分子(即包含未成对电子的分子)原则上可以像普通的条形磁铁一样工作，如果单个未成对电子(微型条形磁铁)的自旋在特定方向上对齐并保持对齐。在实践中，这种行为在室温下是未知的，因为电子的自旋可以在相反的方向上快速翻转，从而失去永久磁性。如何设计出最大限度地提高自旋翻转势垒以使分子磁铁在室温下保持其排列状态的分子是一个令人敬畏的问题。克服这一困难将影响许多依赖于电磁效应的物理现象。这项拟议的研究将通过系统地研究附着在金属上的原子或原子基团如何影响自旋翻转的势垒，来帮助理解控制势垒的因素。这项研究还将涉及对几名本科生、研究生和博士后进行广泛的物理化学技术培训。学生将获得各种技能，从合成高度空气和湿度敏感的化合物到进行复杂的磁性研究。学生还将接触到国内和国际合作，以扩大他们的经验和教育。