LnIII Complexes Displaying ErIII-centered Upconversion Emission in Solution and the Solid State with YbIII, NdIII or a Porphyrin-based ligand as Activators

在化学系化学结构、动力学和机理B （CSDM-B）项目的支持下，德克萨斯理工大学的Anne E. V. Gorden、内华达大学里诺分校的Ana de Bettencourt-Dias和加州理工州立大学洪堡分校的Jorge Monteiro将研究镧系元素与铒、镱和钕的配合物，以开发新的化合物，这些化合物在固态和溶液中都有可能显示有效的上转换发射。在双光子上转换中，低能量的非破坏性波长的光，如红外光，通过材料激发机制在电磁波谱的可见区域转换成高能量的发射。这些新型金属配合物作为水溶性化合物的开发有望使其成为新的发光探针，用于实时细胞生物成像，而无需使用破坏性的高能辐射。从长远来看，这种研究有可能为生物医学科学开辟新的前景，因为它为研究细胞和生物组织中的过程提供了有利的工具，而不会扰乱生物学。例如，这种复合物可能提供一种分析活组织中代谢过程或金属酶反应性的新方法，从而为健康细胞生物学和功能失调细胞生物学引入新的读数，作为一种可能的诊断工具。虽然存在固态上转换发射的选定例子，但溶液中有效上转换发射的参数尚未很好地确定。为了探测这些参数，Gordon研究小组将分离多金属Ln(III)-离子配合物与水溶性萘基配体和预组织的超分子结构，并表征它们的光物理性质。Ln（III）离子具有长寿命发射的特征谱线，可以很容易地与背景荧光区分开。重要的是，毒性和低细胞穿透性不是Ln(III)-配合物固有的问题，这些配合物的发射特性不依赖于它们的晶相。为了实现上转换发射，需要配合物中Yb（III）和Er（III）或Nd（III）和Er（III）的组合，需要仔细平衡必要的化学计量。利用精心设计的系统，Gordon博士和她的团队将调整Ln（III）离子复合物的性质，以改善溶解度、生物相容性和光物理性质。最理想的是，这种探针应该是水溶性的，在容易与组织和细胞荧光区分的发射波长下显示高发射效率，并且应该在不被生物组织吸收或损害生物组织的波长下激发。这项工作有望有助于更好地理解导致固态和溶液中上转换发射增加的结构-发光关系。从这项工作中获得的见解有可能帮助指导有效的新型发光探针的设计和开发，最终应用于生物成像。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Chemical Structure, Dynamics, and Mechanisms B (CSDM-B) program in the Division of Chemistry, Anne E. V. Gorden of Texas Tech University, Ana de Bettencourt-Dias of the University of Nevada, Reno, and Jorge Monteiro of California Polytechnic State University-Humboldt will study lanthanide complexes with erbium, ytterbium, and neodymium to develop new compounds that have the potential to display efficient upconversion emission both in the solid state and in solution. In two-photon upconversion, light of lower energy non-destructive wavelengths, such as infrared light, is converted to higher energy emission in the visible region of the electromagnetic spectrum through a materials-excitation mechanism. The development of these new metal complexes as water-soluble compounds is expected to enable their application as new luminescent probes for bio-imaging of cells in real time without the need to employ damaging, high-energy radiation. In the long term, such studies have the potential to open up new vistas for biomedical science, by providing enabling tools to study processes in cells and biological tissues without perturbing the biology. Such complexes might, for example, provide a new means of analyzing metabolic processes or the reactivity of metalloenzymes in living tissues, thereby introducing new readouts for both healthy cell biology and dysfunctional cell biology, as a possible diagnostic tool.While selected examples of Ln(III)-upconversion emission in the solid state exist, the parameters for efficient upconversion emission in solution are not well established. To probe these parameters, the Gordon research team will isolate multi-metallic Ln(III)-ion complexes with water-soluble naphthylsalophen-based ligands and pre-organized supramolecular structures and characterize their photophysical properties. Ln(III)-ions have characteristic line-like spectra with long-lived emission, which can be easily distinguished from background fluorescence. Importantly, toxicity and low cell penetrability are not inherent concerns with Ln(III)-complexes and the emission properties of these complexes are not dependent on their crystalline phase. To realize upconversion emission, a combination of Yb(III) and Er(III) or Nd(III) and Er(III) in the complexes is needed, requiring careful balance of the necessary stoichiometry. Using judiciously designed systems, Dr. Gordon and her team will tune the properties of the Ln(III)-ion complexes for improved solubility, biocompatibility, and photophysical properties. Optimally, such probes should be water-soluble, display high emission efficiencies at emission wavelengths that are easily discriminated from tissue and cell fluorescence, and should be excited at wavelengths that are not absorbed by or damaging to biological tissues. This work is expected to contribute to better understanding of the structure-luminescence relationship that leads to increased upconversion emission in the solid state and in solution. The insights gained from this work have the potential to help guide the design and development of effective new luminescent probes, ultimately for applications in biological imaging.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.