Smart Photochromic Electronic Devices: Incorporation of a Bicyclic Aziridine in Organic Semiconducting Materials

在化学系大分子、超分子和纳米化学项目的支持下，德克萨斯大学达拉斯分校的Michael C.Biewer正在开发一种基于含氮芳香分子的光致变色装置。合成的单元将以侧基的形式连接到半导体有机材料上，随后将其延伸成共轭的给体-受体-给体小分子。半导体材料是以含硫共轭芳香族体系(称为噻吩类)为基础构建的。所制备的有机分子的超分子堆积有望导致材料在施加外部电压(类似晶体管的行为)或光线照射(类似光伏电池的行为)时成为导电材料。为了系统地研究和最大化在光照射下光电性质的变化，将执行各种合成操作。这项研究有可能产生新型的光激活和刺激响应材料和聚合物，这些材料和聚合物在智能有机电子设备中具有潜在的长期应用，包括显示和传感器技术。从事这个项目的本科生和研究生将在有机化学和材料化学以及工程学方面培养广泛的技能。将创建一个应用程序，以帮助在远程环境中教授有机化学主题。相应的网站将提供更多更广泛的教育内容，并将通过上载关于对有机反应的机理理解的视频进行扩展。外展和教育活动将包括通过德克萨斯大学达拉斯分校的学者日活动和暑期研究计划与当地高中进行互动。在大学层面，Biewer教授将继续指导来自墨西哥大学的暑期交换生，并在整个自然科学学院和数学学院教授有关功能材料和聚合物主题的专业知识。在保持最佳固态性能所需构象需求的同时，外部调制pi共轭超分子组件和聚合物的光电特性的能力，是现代有机电子学面临的重要挑战。本项目将侧重于将一种基于双环氮杂环系统的新型光致变色单元引入到功能噻吩类化合物中的合成方面。具体目标将集中在(A)合成具有施主-受体-施主骨架的半导体有机小分子，该骨架包含一个连接到噻吩核的双环氮杂环单元，(B)修饰连接到双环氮杂环单元的共轭核心，以最大限度地改变光致变色状态的迁移率，以及(C)将小的光致变色分子掺入光电子器件中，以在应用光的情况下创建智能器件。有机合成战略将得到计算建模的补充。一般而言，所获得的知识可能适用于聚噻吩类和其他聚苯硫醚共轭聚合物的功能化。这项研究有可能对双环氮杂环丁光开关的各种结构-性质关系以及它们影响有机电子电子性质的能力产生新的见解。设计合成方法，将双环氮杂环单元结合到导电材料中，结合主干上的电子迁移率，可以创建刺激响应性有机材料和聚合物。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 program in the Division of Chemistry, Michael C. Biewer of the University of Texas at Dallas is developing a photochromic unit based on aromatic molecules that contain nitrogen. The synthesized unit will be attached as a pendant group to a semiconducting organic material, which will subsequently be extended into a conjugated donor-acceptor-donor small molecule. Semiconducting materials are to be constructed based on sulfur-containing conjugated aromatic systems known as thiophenes. Supramolecular stacking of the prepared organic molecules is expected to lead to materials that can become conductive when external voltage is applied (transistor-like behavior) or light shines on them (photovoltaic cell-like behavior). A variety of synthetic manipulations will be performed in order to systematically investigate and maximize the changes in optoelectronic properties upon irradiation with light. This research has the potential to generate novel light-activated and stimuli responsive materials and polymers with potential long term applications in smart organic electronics, including display- and sensor-technology. Undergraduate and graduate students working on this project will develop a broad range of skills in organic and materials chemistry, as well as engineering. An application will be created to aid in teaching organic chemistry topics in a remote environment. The corresponding website will provide additional broader educational content and will be expanded by uploading videos on mechanistic understanding of organic reactions. Outreach and educational activities will include interactions with local high schools through Scholar’s Day events at the University of Texas at Dallas and through summer research program. At the university level, Professor Biewer will continue to direct summer exchange students from Mexican universities and educate majors throughout the school of natural sciences and mathematics on the topic of functional materials and polymers.The ability to externally modulate optoelectronic properties of pi-conjugated supramolecular assemblies and polymers, while maintaining conformational demands needed for optimal solid state-performance, is an important challenge for modern organic electronics. This project will focus on the synthetic aspects of the incorporation of a novel photochromic unit based on a bicyclic aziridine ring system into functional thiophenes. Specific objectives will concentrate on (a) the synthesis of semiconducting small organic molecules with a donor-acceptor-donor framework that contains a bicyclic aziridine unit conjugated to the thiophene core, (b) modifications of the conjugated core connected to the bicyclic aziridine unit to maximize change in mobility in photochromic states and (c) incorporation of small photochromic molecules into optoelectronic devices to create smart devices upon application of light. Organic synthetic strategies will be complemented by computational modeling. The knowledge gained will likely be applicable to the functionalization of polythiophenes and other pi-conjugated polymers, in general. The research has the potential to yield new insights into various structure-property relationships of bicyclic aziridine photoswitches and their ability to influence the electronic properties of organic electronics. Designing synthetic methods to incorporate the bicyclic aziridine unit within a conducting material, in conjunction with the electronic mobility along the backbone, may allow the creation of stimuli responsive organic materials and polymers.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.