Complexes in which sp Carbon Chains span two Metals

本项目的目标是合成钢丝状sp杂化碳链跨越两个过渡金属片段的配合物，并对其化学和物理性质进行详细的研究。在非常长的链长度上，这些材料与金刚石和石墨，经典的三维和二维sp3和sp2杂化聚合物碳同素异形体有着很强的概念关系。它们也比具有有机端基的类似物稳定得多。人们将逐渐寻求基于这些构建块的更复杂的体系结构。其中一个目标是具有C32-C40链的配合物，其中金属-金属距离将超过5纳米；具有C24-C28链的碳链易于分离，并且在140℃下稳定。在另一项研究中，Cx链将通过两个灵活的sp3碳链在每个末端上跨越给原子来进行空间保护。当足够长时，它们采用手性双螺旋结构，很像家用电线的绝缘。这些物质的氧化还原特性将被研究；预计混合价基离子的稳定性将得到提高。其他涉及轮烷的空间屏蔽sp链的方法将被研究。在另一项努力中，将合成具有平行Cx链的这种配合物的横向阵列或“束”。这些可以看作是多链分子线。在另一项工作中，将准备定义良好的纵向扩展数组，例如PtCxPtCxPtCxPt物种。将在终端铂原子上引入“鳄鱼夹”，这样就可以测量单分子电导率。与螯合二膦的反应可能会引入“扭结”，这种“扭结”可能允许（在适当条件下）PtC3xPt物种的还原消除或每个角含有铂原子的多边形的氧化偶联。用单铂的氧化偶联法制备多边形。人们将尝试挤压铂原子，生成环碳Cx（一种单体碳同素异形体）。C=C基团的反应将被研究，如三甲基化到六取代苯和甲基化得到奇碳物种M(C=C)n‘C=M’。在合作的努力下，每个家族的配合物的NLO和光物理性质将被表征。将特别注意定义链长度效应和链-链相互作用。如何将这些线状不饱和分子设计成各种复杂结构的详细知识将会产生。通过这个奖项，有机和大分子化学项目支持了德克萨斯农工大学化学系约翰·a·格拉迪斯教授的研究。Gladysz教授和他的学生正在探索含有金属原子覆盖的延伸碳链的分子的合成和性质。这些系统模拟了当前相当受关注的全碳系统。它们有望在分子线、非线性光学材料和其他更复杂的分子聚集体的设计和构建中显示出各种不同寻常的潜在相关特性。参与该项目的学生将有机会与德国学生和专门从事分子材料表征的物理化学家合作。

The objective of this project is to synthesize complexes in which wire-like sp-hybridized carbon chains span two transition metal fragments, and to conduct detailed studies of their chemical and physical properties. At very long chain lengths, such materials bear a strong conceptual relationship to diamond and graphite, the classical three- and two-dimensional sp3 and sp2-hybridized polymeric carbon allotropes. They are also much more stable than analogs with organic endgroups. Progressively more complex architectures based upon such building blocks will be sought. In one effort, complexes with C32-C40 chains, in which the metal-metal distances would surpass 5 nm, will be targeted; those with C24-C28 chains are easily isolable and stable to 140 C. In another effort, the Cx chain will be sterically protected via two flexible sp3 carbon chains that span donor atoms on each terminus. When sufficiently long, these adopt chiral double helical conformations, much like the insulation about household electrical wire. The redox properties of such species will be studied; it is anticipated that the stabilities of mixed valence radical ions will be enhanced. Other approaches to sterically shielded sp chains involving rotaxanes will be investigated. In another effort, lateral arrays or "bundles" of such complexes with parallel Cx chains will be synthesized. These can be viewed as multi-stranded molecular wires. In another effort, well-defined longitudinally extended arrays, such as PtCxPtCxPtCxPt species, will be prepared. "Alligator clips" will be introduced on the terminal platinum atoms such that single-molecule conductivities can be measured. Reactions with chelating diphosphines may introduce "kinks" that might allow (under appropriate conditions) reductive eliminations to PtC3xPt species or oxidative couplings to polygons that contain platinum atoms at each corner. Polygons will also be prepared by oxidative couplings of monoplatinum species. Attempts will be made to extrude the platinum atoms, generating a cyclocarbon Cx (a monomeric carbon allotrope). Reactions of the C=C moieties will be investigated, such as trimerizations to hexasubstituted benzenes and metatheses to give odd-carbon species M(C=C)n'C=M'. In collaborative efforts, the NLO and photophysical properties of each family of complexes will be characterized. Particular attention will be given to defining chain length effects and chain-chain interactions. A detailed knowledge of how to engineer these wire-like unsaturated molecules into a variety of sophisticated architectures will result.With this award, the Organic and Macromolecular Chemistry Program is supporting the research of Professor John A. Gladysz, of the Department of Chemistry at Texas A&M University. Professor Gladysz and his students are exploring the synthesis and properties of molecules containing extended carbon chains capped by metal atoms. These systems mimic all-carbon systems of considerable current interest. They are expected to display a variety of unusual properties of potential relevance in the design and construction of molecular wires, nonlinear optical materials, and other more complex molecular aggregates. Students involved in this project will have the opportunity to collaborate with students in Germany and with physical chemists specializing in the characterization of molecular materials.