Luminescent Organometallic Complexes with Fast Radiative Rates

在化学系化学结构、动力学机制-B（CSDM-B）项目的支持下，休斯顿大学化学系的托马斯·蒂茨正在研究提高磷光金属络合物辐射衰减速率的策略。磷光体金属络合物已用于各种光电应用，最值得注意的是有机发光二极管（OLED），这是一种广泛用于彩色显示器和其他消费产品的照明技术。该项目的目标是在几种不同类别的磷光化合物中使用互补的分子设计策略，以提高其辐射率，并对生产具有更高效率和耐用性的OLED产生长期影响。这项工作结合了创新的合成化学来制造新的分子，并深入的物理特性来测量光发射的颜色特征、效率和时间尺度。站在有机金属化学和光化学的界面上，这项研究旨在产生有见地的结构-性质关系，从而发现性能最佳的磷光金属配合物。该项目的另一部分将开发一个公开的光化学活性化合物网络数据库，使各级研究人员能够在数据库中搜索和排序具有特定特性的化合物。最后，该研究项目将作为实验物理无机化学研究的本科生和研究生研究人员的培训基地，为未来的科学和技术劳动力做出贡献。在此奖项下，测试研究团队将追求三个互补的策略，以提高有机金属磷光体的辐射率和光致发光量子产率。前两个重点是蓝色磷光，这仍然是光电领域最重要的技术挑战之一。乙炔化铂化合物是一类很有前途的蓝色磷光化合物，但其缓慢的辐射速率阻碍了其在OLED中的广泛应用。该项目将采用“二次重金属效应”，通过用其他重金属装饰铂芳基乙炔化合物的外围，作为提高辐射率的一种策略。这些方法集中在吡啶基取代的乙炔基上，其可以与各种重金属添加剂配位，钴金属直接与乙炔基π-电子结合，以及在芳基乙炔基配体上形成共价金-碳键。虽然有机铂配合物是这项工作的主要重点，第二个战略的蓝色磷光与快速辐射速率将涉及一类新的环化铱乙炔化合物。这些化合物将联合收割机结合源自芳基乙炔的有利的锐利蓝色磷光与铱产生的固有较大的自旋-轨道耦合和较快的辐射速率。最后，该项目的最后一个主要重点是环化铂配合物，重点是光谱中较低能量区域（红色到近红外）的发光。这些化合物将具有富含电子的辅助配体，可以稳定电荷转移状态，增加激发态自旋轨道耦合，并增加辐射速率常数。空间效应的环化和辅助配体也将被调查，是重要的最大限度地减少聚集和抑制nonradiative rates.This奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的智力价值和更广泛的影响审查标准。

WIth support from the Chemical Structure, Dynamics & Mechanisms-B (CSDM-B) Program of the Chemistry Division, Thomas Teets of the Department of Chemistry at University of Houston is investigating strategies to increase the radiative decay rates in phosphorescent metal complexes. Phosphorescent metal complexes have been used in a variety of optoelectronic applications, most notably organic light-emitting diodes (OLEDs), a lighting technology that is widely used in color displays and other consumer products. The goal of this project is to use complementary molecular design strategies in a few different classes of phosphorescent compounds to increase their radiative rates, with long-term implications of producing OLEDs with improved efficiency and durability. The work combines innovative synthetic chemistry to make new molecules and in-depth photophysical characterization to measure the color profile, efficiency, and timescale of light emission. Standing at the interface of organometallic chemistry and photochemistry, this research aims to produce insightful structure-property relationships that lead to the discovery of top-performing phosphorescent metal complexes. Another part of this project will develop a publicly available web database of photochemically active compounds, allowing researchers at all levels to search and sort the database for compounds that have specific properties of interest. Finally, this research project will serve as a training ground for undergraduate and graduate researchers in experimental physical inorganic chemistry research to contribute to the future science and technology workforce.Under this award, the Tests research team will pursues three complementary strategies for increasing the radiative rates and photoluminescence quantum yields of organometallic phosphors. The first two focus on blue phosphorescence, which remains one of the most significant technical challenges in the optoelectronic field. Platinum acetylide compounds are a promising class of blue-phosphorescent compounds, but their slow radiative rates have hindered their widespread deployment in OLEDs. This project will introduce the “secondary heavy-metal effect” as a strategy to increase radiative rates, by decorating the periphery of platinum aryl acetylide compounds with other heavy metals. These approaches center on pyridyl-substituted acetylides which can coordinate to a variety of heavy metal additives, binding of coinage metals directly to the acetylide π-electrons, and covalent gold-carbon bond formation on the aryl acetylide ligands. Although organoplatinum complexes are the major focus of this work, a second strategy for blue phosphorescence with fast radiative rates will involve a new class of cyclometalated iridium acetylide compounds. These compounds will combine the advantageous sharp blue phosphorescence originating from aryl acetylides with the inherently larger spin-orbit coupling and faster radiative rates that iridium engenders. Finally, the last major thrust of this project centers on cyclometalated platinum complexes, with an emphasis on luminescence in the lower-energy regions (red to near-infrared) of the spectrum. These compounds will feature electron-rich ancillary ligands that can stabilize charge-transfer states, increase excited-state spin-orbit coupling, and augment radiative rate constants. Steric effects on both the cyclometalating and ancillary ligand will also be investigated and are important for minimizing aggregation and suppressing nonradiative rates.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.