Novel Cation Radical and Exciplex Chemistry

新型阳离子自由基和激基复合物化学

• 批准号: 1464729
• 负责人: Joseph Dinnocenzo
• 金额: $ 55万
• 依托单位: University of Rochester
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-08-01 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1464729&HistoricalAwards=false
• 关键词: Novel; Cation; Radical; Exciplex; Chemistry

With this award, the Chemical Structure, Dynamics, and Mechanism B Program is supporting Professor Joseph P. Dinnocenzo at the University of Rochester to investigate the selective formation of highly reactive aryl radicals under mild conditions. The mechanistic insight gained from these studies can provide the knowledge necessary to rationally utilize the chemistry in synthesis and in the design of new materials. In addition, research on newly discovered cationic exciplexes and exciplexes that exhibit dual emissions will provide knowledge on these novel excited state intermediates. Research to better understand the fundamental photophysical properties these exciplexes intermediates will provide valuable knowledge for the design of efficient photoinduced electron transfer reactions and for potential use in sensing applications. Student co-workers will learn to carry out chemical syntheis and to conduct mechanistic studies in photochemistry. including a range of less traditional techniques (fluorometry, transient absorption spectroscopy, time-correlated single photon counting, electrochemistry, and modern computational methods). Thus, students trained with NSF support will be well prepared to tackle a variety of multidisciplinary problems in their professional, scientific careers.This project will also benefit undergraduate students through the NSF REU summer program at the University of Rochester with particular attention paid to recruiting students from groups traditionally underrepresented in science and engineering.Recent work in the Dinnocenzo laboratory has revealed that aryltrialkylstannane cation radicals undergo nucleophile-assisted fragmentation reactions in which less stable aryl radicals are often formed in preference to more stable alkyl radicals - an seemingly contrathermodynamic result. This selectivity is unprecedented in ion radical chemistry. Proposed research will test the generality of these remarkable results by exploring the fragmentation reactions of aryltrialkyl-germane and -silane cation radicals through the combined use of synthesis, steady-state photooxidation experiments, and nanosecond transient absorption spectroscopy. In addition, two types of novel, charge-transfer exciplex intermediates recently discovered in the Dinnocenzo laboratory will be investigated. One type of exciplex is formed by reaction of cationic, excited state acceptors with neutral donors, which leads to the formation of emissive cationic exciplexes that are without precedent. Research objectives include determining the electronic nature of the exciplexes (e.g. electronic coupling matrix elements) through theoretical fitting of the radiative lifetimes of the exciplexes (determined by time-correlated single photon counting) and their fluorescence spectra, exploring the generality of cationic exciplexes, and measuring some of their photophysical properties. A related project will investigate examples uncovered in the PI's lab where two exciplex emissions are observed from a single acceptor and donor. Preliminary results indicate dramatically different solvent reorganization energies for the two types of exciplexes. Proposed research will determine the electronic properties of the exciplexes and explore their generality.

凭借该奖项，化学结构、动力学和机制 B 项目正在支持罗切斯特大学的 Joseph P. Dinnocenzo 教授研究在温和条件下选择性形成高反应性芳基自由基。从这些研究中获得的机理见解可以提供在新材料的合成和设计中合理利用化学所需的知识。此外，对新发现的阳离子激基复合物和表现出双重发射的激基复合物的研究将提供有关这些新型激发态中间体的知识。更好地了解这些激基复合物中间体的基本光物理性质的研究将为有效光诱导电子转移反应的设计和传感应用的潜在用途提供宝贵的知识。 学生同事将学习进行化学合成并进行光化学的机理研究。包括一系列不太传统的技术（荧光测定法、瞬态吸收光谱法、时间相关单光子计数、电化学和现代计算方法）。因此，在 NSF 支持下接受培训的学生将做好充分准备，以解决其专业、科学生涯中的各种多学科问题。该项目还将通过罗切斯特大学的 NSF REU 暑期项目使本科生受益，特别注重招生来自传统上在科学和工程领域代表性不足的群体。Dinnocenzo 实验室的最新工作表明，芳基三烷基锡烷阳离子自由基会发生亲核试剂辅助的断裂反应，其中通常会形成不太稳定的芳基自由基优先于更稳定的烷基——这似乎是反热力学的结果。这种选择性在离子自由基化学中是前所未有的。拟议的研究将通过综合使用合成、稳态光氧化实验和纳秒瞬态吸收光谱来探索芳基三烷基-锗烷和-硅烷阳离子自由基的裂解反应，从而测试这些显着结果的普遍性。此外，还将研究 Dinnocenzo 实验室最近发现的两种新型电荷转移激基复合物中间体。一种类型的激基复合物是通过阳离子激发态受体与中性供体的反应形成的，这导致形成前所未有的发射性阳离子激基复合物。研究目标包括通过激基复合物的辐射寿命（由时间相关的单光子计数确定）及其荧光光谱的理论拟合来确定激基复合物（例如电子耦合矩阵元素）的电子性质，探索阳离子激基复合物的普遍性，以及测量它们的一些光物理特性。一个相关项目将调查 PI 实验室中发现的示例，其中从单个受体和供体观察到两个激基复合物发射。初步结果表明两种类型的激基复合物的溶剂重组能显着不同。拟议的研究将确定激基复合物的电子特性并探索其通用性。