Molecular design of novel luminescent complexes based on hybrid phosphine ligands for chemo- and biosensing applications

这一联合项目旨在为化学、生物传感和生物成像应用提供基于一类新型多施主杂化含磷杂环及其过渡金属络合物的新型发光系统。主要的合成努力将针对含有两个内环磷(III)原子、两个外环发色基团和两个位于内环氮原子上的可调功能的环膦配体，以在低成本的框架内允许最大的合成灵活性。这些化合物将通过初级杂芳基膦与甲醛的缩合反应以及随后通过添加伯胺或氨基酸形成环来合成。磷和氮上的变色杂环取代基为超分子组装提供了发光性能和额外的结合位置。内环氮原子上的不同取代基也将被用来改变给体中心的空间和电子性质，并将同时提供微调物理性质的手段，如配体的亲脂性、亲水性和发光。金属络合物的光学性质取决于生色团和金属离子的类型。采用不同配位数和配位球的D6、D8和D10金属离子(Ir(III)、Pt(II)、Au(I)和Cu(I))可以得到不同的发光参数。为了有效的电荷转移和高发光，发色基团应该配位到金属中心或靠近金属中心。此外，一些发色配体将被配位在金属中心以修饰络合物的光物理性质。目标化合物的独特结构将为其底物诱导的发光响应提供基础，这反过来又是氧化还原转换或主客体络合物形成的结果。将对合成的配合物进行电子结构的量子化学研究，目的是揭示导致电子吸收和发光的跃迁所涉及的轨道。在了解光谱起源及其结构-性质关系的基础上，将评估发光金属络合物开发各种功能和应用的潜力，特别是在生物成像和生物传感领域的潜力。由于络合物在水中的不溶性可能会限制其在生物成像和生物传感方面的适用性，因此这些络合物也将转化为水溶性亲水纳米颗粒用于这些研究。

This joint project aims to provide access to novel luminescent systems based on a new class of multidonor hybrid phosphorus-containing heterocycles and their transition metal complexes for applications in chemo- and biosensing and bioimaging. The main synthetic efforts will be directed towards cyclic phosphine ligands containing two endocyclic phosphorus(III) atoms, two exocyclic chromophoric groups, and two tunable functions located on the endocyclic nitrogen atoms to allow maximal synthetic flexibility within a low-cost framework. These compounds will be synthesized by condensation reactions of primary heteroaryl phosphines with formaldehyde and subsequent ring formation through addition of primary amines or amino acids. Chromophoric heteroaromatic substituents at phosphorus and nitrogen provide luminescence properties and additional binding sites for supramolecular assemblies. Differing substituents on the endocyclic nitrogen atoms will also be used to modify the steric and electronic properties of the donor centers, and will simultaneously provide the means to fine-tune physical properties such as ligand lipo- and hydrophilicity and luminescence. The optical properties of metal complexes depend on the type of chromophore and metal ion. A variety of luminescence parameters will be achieved by employing d6, d8, and d10 metal ions (Ir(III), Pt(II), Au(I) und Cu(I)) with different coordination numbers and coordination spheres. For effective charge transfer and high luminescence, chromophoric groups should be coordinated to the metal center or be located in near proximity. Moreover, a number of chromophoric coligands will be coordinated at the metal center to modify the photophysical properties of the complexes. The unique structure of the targeted complexes will provide a basis for their substrate-induced luminescence response, which in turn results from redox transformations or host–guest complex formation. Quantum chemical investigations of the electronic structure will be performed for the synthesized complexes with the aim of revealing the orbitals involved in the transitions responsible for electronic absorption and luminescence. On the basis of an understanding of the spectroscopic origin and their structure–property relationships, the potential for the development of luminescent metal complexes for a variety of functions and applications, especially in the field of bioimaging and biosensing, will be evaluated. As insolubility of the complexes in water might restrict their suitability for bioimaging and biosensing, these complexes will also be converted to water-soluble hydrophilic nanoparticles for these studies.