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)计划的支持下，诺克斯维尔田纳西大学的Michael S.Kilbey和Brian K.Long正在开发含嘌呤的导电共聚物。嘌呤是含有两个融合在一起的环的芳香化合物。它们是自然界中出现最广泛的含氮杂环，也是DNA和RNA中常见的构件。其他的嘌呤来源包括肉类、酵母、燕麦片和咖啡因。在本项目中，首先将在传统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置反应性。所获得的知识将用于将这些单体与含硫杂环偶联，以制备定义明确的低聚物和完全共轭的共聚物。这些共聚物将被检测其导电和发光的能力，使其成为光电设备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，以产生量化连接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的关系。由此产生的基础化学知识体系有可能刺激以嘌呤为基础的非传统构建块设计和合成共轭聚合物的创新。将通过研究生共同咨询和研究生导师计划的制定和实施来促进教育和培训。此外，来自研究中代表性不足群体的学生将通过国家科学基金会支持的校园项目参与进来。通过为田纳西科学奥林匹克竞赛服务，与年轻学习者和更广泛的公众接触，将促进和培养年轻学习者对科学的兴趣。这项工作将调查分子设计对定义明确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，小分子偶联研究将被用来研究用于形成碳-碳键的位置的反应性偏向在噻吩嘌呤(TPT)三元化合物上。这些研究有望为构建含嘌呤的共聚物提供关键的见解，并通过这种方式为创建定义明确的含嘌呤低聚物和共聚物的努力提供信息。第二个目标将集中在三聚体的合成和表征上，这些三聚体在嘌呤支架上具有明确的连接性模式(2，6-，6，8-和2，8-连接性)，但具有区域化学上的系统性差异。在最后一个目标中，通过TPT三元化合物的直接(异)芳基化聚合，采用AB聚合或AA+BB共聚，合成了线性共轭和交叉共轭的嘌呤-噻吩共聚物。这一研究计划的结果预计将为利用分子设计来调节共轭聚合物的纳米级组装和性质的努力提供信息和激励，由于其作为有机半导体的功能，这些聚合物在各种环境中都适用。除了推进分子工程方法来理解新型功能聚合物的行为和特性外，这项工作还有可能提供基础知识，以扩大生物衍生和有机电子中丰富的嘌呤的潜力。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势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.