CAS: Synthesis, Assembly and Photophysical Behaviors of Nonconventional Purine-Containing Conjugated Copolymers

在化学系大分子、超分子和纳米化学（MSN）项目的支持下，田纳西大学诺克斯维尔分校的Michael S. Kilbey和Brian K. Long正在开发导电的含嘌呤共聚物。嘌呤是由两个环融合在一起的芳香族化合物。它们是自然界中最广泛存在的含氮杂环，是DNA和RNA中常见的组成部分。其他嘌呤来源包括肉类、酵母、燕麦片和咖啡因。在本项目中，将首先在常规偶联反应的基础上进行小分子化学，以了解含嘌呤单体的位点反应性。所获得的知识将用于将这些单体与含硫杂环偶联，以制备定义良好的低聚物和完全共轭的共聚物。共聚物的导电和发光能力将被测试，使其成为光电器件或成像和传感应用的潜在候选者。还将进行一系列光物理和结构表征，以产生关系，量化连通性和区域化学如何影响溶液和固态中的自组装，以及它们如何影响光物理性质。由此产生的基础化学知识体系有可能刺激设计和合成基于嘌呤的非常规构建块的共轭聚合物的创新。通过研究生联合指导和研究生指导计划的制定和实施，促进教育和培训。此外，来自研究中代表性不足群体的学生将通过已建立的nsf支持的校园项目参与其中。通过为田纳西州科学奥林匹克竞赛服务，与年轻学习者和更大的公众接触，将促进和培养年轻学习者对科学的兴趣。本研究将探讨分子设计对定义良好的低聚物和完全共轭的含嘌呤聚合物的构象、组织和性质的作用。在第一个目标中，小分子偶联研究将用于研究噻吩-嘌呤-噻吩（TPT）三联体上碳-碳键形成位点的反应性偏差。这些研究有望提供关于如何构建含嘌呤共聚物的关键见解，并以这种方式为创建定义明确的含嘌呤低聚物和共聚物提供信息。第二个目标将集中于三聚体的合成和表征，这些三聚体在嘌呤支架上具有明确的连接模式（2,6-,6,8-和2,8-连接），但具有系统的区域化学变化。最后，在最后一个目标中，线性共轭和交叉共轭嘌呤-噻吩共聚物将通过TPT三元直接（异）芳基化聚合使用AB聚合或AA+BB共聚合成。该研究项目的结果预计将为利用分子设计来调节纳米级组装和共轭聚合物的性质提供信息和激励，共轭聚合物由于其作为有机半导体的功能而在各种情况下都具有适用性。除了推进分子工程方法来理解新型功能聚合物的行为和性质外，这项工作还有可能提供基础知识，扩大生物衍生和丰富的嘌呤在有机电子学中的潜力。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 Macromolecular, Supramolecular and Nanochemistry (MSN) program in the Division of Chemistry, Michael S. Kilbey and Brian K. Long of the University of Tennessee, Knoxville are developing conductive purine-containing copolymers. Purines are aromatic compounds that contain two rings fused together. They are the most widely occurring nitrogen-containing heterocycles in nature and are common building blocks found in DNA and RNA. Other purine sources include meats, yeast, oatmeal and caffeine. In this project, small molecule chemistry will first be performed based on conventional coupling reactions in order to understand site reactivity of purine-containing monomers. The knowledge gained will then be used to couple these monomers with sulfur-containing heterocycles to prepare well-defined oligomers and fully conjugated copolymers. The copolymers will be examined for their ability to conduct electricity and emit light, making them potential candidates for optoelectronic devices or for imaging and sensing applications. A suite of photophysical and structural characterizations will also be performed to generate relationships that quantify how connectivity and regiochemistry affect self-assembly in solution and in the solid state, as well as how they influence photophysical properties. The resulting body of fundamental chemistry knowledge has the potential to spur innovations in the design and synthesis of conjugated polymers from nonconventional building blocks based on purines. Education and training will be promoted through co-advising of graduate students and the development and implementation of graduate student mentoring program. Additionally, students from underrepresented groups in research will be involved through established NSF-supported on-campus programs. Engagement with young learners and the greater public through service to the Tennessee Science Olympiad will promote and nurture interests of young learners in science.This work will investigate the role of molecular design on the conformation, organization and properties of well-defined oligomers and fully conjugated purine-containing polymers. In the first objective, small molecule coupling studies will be used to investigate reactivity bias of the sites used for carbon-carbon bond formation on the thiophene-purine-thiophene (TPT) triads. These studies are expected to provide critical insights into how purine-containing copolymers are constructed and, in this way, inform efforts to create well-defined purine-containing oligomers and copolymers. The second objective will focus on the synthesis and characterization of trimers with defined patterns of connectivity across the purine scaffold (2,6-, 6,8-, and 2,8-connectivity), but featuring systematic variation in regiochemistry. Finally, in the last objective, linearly conjugated and cross-conjugated purine-thiophene copolymers will be synthesized via direct (hetero)arylation polymerization of TPT triads using either AB polymerizations or AA+BB copolymerizations. Outcomes from this research program are anticipated to inform and stimulate efforts to use molecular design to modulate nanoscale assembly and properties of conjugated polymers, which find applicability in various contexts due to their functionality as organic semiconductors. In addition to advancing a molecular engineering approach to understand behaviors and properties of novel, functional polymers, this work has the potential to provide fundamental knowledge that expands the potential of bio-derived and abundant purines in organic electronics.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.