Structural, host-guest and chiroptical properties of large coordination cages

在有利的情况下，桥接配体（其可以与两个或三个金属离子配位）和第一行过渡金属离子如Co（II）或Zn（II）的简单组合可以自组装以产生美丽且精细的高对称性配位络合物，其具有复杂的多面体结构，其复杂性与组成部分的简单性不成比例。我们已经准备和结构特征的拓扑结构，如cuboctahedra和截断四面体的许多这样的例子。本研究的目的是研究新笼的合成和结构，并利用它们不寻常的性质，如发光，光学活性和主客体化学，除了在它们的结构和形成它们的自组装过程的兴趣，这些笼是theur的主客体化学的兴趣，因为它们包含大的中心空腔，可以结合带负电荷的物种作为“客人”。对于较小的笼，这些客人可能是简单的抗衡离子，如氟硼酸盐;对于较大的笼，整个带负电荷的金属络合物可能适合在空腔中，给出“络合物的络合物”。有证据表明，阴离子客人实际上模板组装的笼在他们周围，这样使用不同的阴离子可以提供不同的笼超结构。这些笼有可能作为大小和形状选择性的主机阴离子金属配合物作为guests.Another感兴趣的笼的物理性质是它们的发光，因为许多配体含有发光间隔单元，如萘，其性质被修改时，个别配体组装成一个笼。因此，发光可用作监测融合器组装的工具。此外，激发态能量或电子从笼超结构转移到金属络合物客人是可能的，导致发光的外观从客人以下的能量转移从它周围的笼。最后，可以利用笼的光学活性（手性）。在许多情况下，所有的金属三螯合中心具有相同的手性，因此笼是高度手性的。我们将利用这一点，通过使用（i）手性阴离子作为客人解决的笼;（ii）手性阴离子作为模板，给大会的一个单一的对映异构体的笼从非手性组分;和（iii）手性配体（与蒎烯取代基），以合成光学纯的笼，它应该有极高的旋光度，并应作为选择性主机的一个对映异构体的手性客体阴离子。

In favourable circumstances simlle combinations of bridging ligands (which can coordinate to two or three metal ions) and first-row transition metal ions such as Co(II) or Zn(II) can self-assemble to give beautiful and elaborate high-symmetry coordination complexes, with sophisticated polyhedral structures whose complexity is out of all proprtion to the simplicity of the component parts. We have prepared and structurally characterised many such examples with topologies such as cuboctahedra and truncated tetrahedra. This study aims both to investigate the syntheses and structures of new cages, and to exploit their unusual properties such as luminescence, optical activity, and host-guest chemistry.In addition to the interest in their structures and the self-assembly processes which form them, these cages are of interest for theur host-guest chemistry, as they contain large central cavities which can bind negatively-charged species as 'guests'. For the smaller cages these guests may be simple counter-ions such as fluoroborate; for larger cages it may be possible for an entire negatively-charged metal complex to fit in the cavity, giving a 'complex of a complex'. There is evidence to suggest that the anionic guests actually template the assembly of the cage around them, such that use of a different anion may afford a different cage superstructure. THese cages have the potential to act as size- and shape-selective hosts for anionic metal complexes as guests.Another physical property of the cage which is of interest is their luminescence, because many of the ligands contain luminescent spacer units such as naphthalene, whose properties are modified when the individual ligands assemble into a cage. Thus, luminescence can be used as a tool to monitor cage assembly. In addition, transfer of excited-state energy or electrons from the cage superstructure to the metal complex guests is possible, leading to the appearance of luminescence from the guest following energy-transfer from the cage around it.Finally, the optical activity (chirality) of the cages can be exploited. In many cases, all of the metal tris-chelate centres have the same chirality and the cages are accordingly highly chiral. We will exploit this by using (i) chiral anions as guests to resolve the cages; (ii) chiral anions as templates to give assembly of a single enantiomer of the cage from achiral components; and (iii) chiral ligands (with pinene substituents) to synthesise optically pure cages which should have extremely high optical rotations and which should act as selective hosts for one enantiomer of a chiral guest anion.