Metalloporphenes: Synthesis and Characterization

在这个项目中，由化学部的化学结构，动力学机制B计划资助，博尔德科罗拉多大学化学系的Josef Michl教授正在将各种金属离子引入一种类似于单层石墨烯（铅笔中发现的一种碳）的新型聚合物薄片（单原子层厚）中，并探索由此产生的化学性质。 与石墨烯一样，石墨烯由完全稠合的六元碳（苯环）环组成，新的二维聚合物，卟啉，由一系列由大环杂环，卟啉（含有碳，氮和通常的金属）组成的稠环组成。 与石墨烯不同，卟啉可以在不去除键的情况下进行修饰，这导致其特殊的电子或反应性特性。这项研究的目标是利用这种最近制备的不寻常材料的预期特性，用于开发新的电催化剂和光催化剂，用于水分解，将二氧化碳转化为燃料，以及其他允许将太阳能转化为储存的化学能的过程。 该项目位于有机，无机和材料化学的界面。 Michl教授的小组有能力为科学代表性不足的学生提供最高水平的教育和培训，并通过外展活动唤起K-12学生对科学的兴趣。 像石墨烯一样，它由完全共轭的稠合苯环组成，新的二维聚合物，卟啉，由一系列完全共轭的稠合环组成，这些稠合环由大环杂环卟啉组成。 与石墨烯不同，卟啉可以在不去除参与其π电子系统的任何原子的共轭的情况下被官能化。 这种功能化的灵活性是通过将金属离子插入卟啉环的中心来实现的。 类似于普通的单体卟啉，在卟啉中的金属离子可能能够携带两个，一个或零个几乎任意结构的配体，允许母体游离碱卟啉转化成一个大家族的二维金属聚合物，具有容易调节的化学，电化学和光化学催化性能。合成包括设计用于探测分子结构和各种催化性质之间的关系的修改。 该研究解决了几个问题：如何将目前可用的双层porphene剥离成单层？ 哪种过渡金属离子和主族金属离子可以插入自由基的卟啉层，在什么条件下它们可以被移除？ 这些金属离子可以携带哪些配体？ 其他的问题也在研究卟啉的反应性：在卟啉中所含的金属离子上发生的反应与那些从溶液中普通单体金属卟啉的研究中已知的反应有什么不同？ 任何观察到的反应性可以用来构建催化循环吗？ 该奖项将特别关注金属卟啉用于覆盖吸光材料表面或电极表面的工艺。该奖项反映了NSF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。

In this project, funded by the Chemical Structure, Dynamics & Mechanisms B Program of the Chemistry Division, Professor Josef Michl of the Department of Chemistry at the University of Colorado, Boulder, is introducing various metal ions into a thin sheet (single atomic layer thick) of a new polymer resembling a single sheet of graphene (a form of carbon found in pencils), and exploring the resulting chemical properties. Like graphene, which consists of fully fused six-membered carbon (benzene) rings, the new two-dimensional polymer, porphene, consists of an array of fused rings made up of the macrocyclic heterocycle, porphyrin (which contains carbon, nitrogen and often metals). Unlike graphene, porphene can be modified without removing the bonding which causes its special electronic or reactivity properites. The goal of this research is to exploit the expected characteristics of this very recently prepared, unusual material for the development of new electrocatalysts and photocatalysts for water splitting, conversion of carbon dioxide into fuels, and other processes that permit the conversion of solar energy into stored chemical energy. The project lies at the interface of organic, inorganic, and materials chemistry. Professor Michl's group is well positioned to provide the highest level of education and training for students underrepresented in science and to arouse interest in science among K-12 students through outreach activities. Like graphene, which consists of fully conjugated fused benzene rings, the new two-dimensional polymer, porphene, consists of an array of fully conjugated fused rings made up of the macrocyclic heterocycle, porphyrin. Unlike graphene, porphene can be functionalized without removing the conjugation of any of the atoms that participate in its pi-electron system. This flexibility in functionalization is accomplished by insertion of metal ions into the centers of the porphyrin rings. Similar to the ordinary, monomeric porphyrins, the metal ions in porphene may be able to carry two, one, or zero ligands of almost arbitrary structure, permitting a conversion of the parent free-base porphene into a large family of two-dimensional metallopolymers with easily tuneable chemical, electrochemical, and photochemical catalytic properties. The syntheses include modifications designed to probe the relationships between molecular structures and various catalytic properties. The research addresses several questions: How can the presently available double layer of porphene be exfoliated to single layers? Which transition and main-group metal ions can be inserted into free-base porphene layers and under what conditions are they removed? What ligands can these metal ions carry? Other questions examine the reactivity of porphene: How do the reactions that occur on the metal ions contained in porphene differ from those known from studies of ordinary monomeric metalloporphyrins in solution? Can any of the observed reactivity be utilized to construct catalytic cycles? Particular attention will be paid to processes in which a metalloporphene is used to cover the surface of a light-absorbing material or the surface of an electrode.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.