Exploration of Annulated Phosphorus Heterocycles Derived from Anionic Dicarbenes

阴离子二碳烯衍生的环状磷杂环化合物的探索

• 批准号: 514566227
• 负责人: Privatdozent Dr. Rajendra S. Ghadwal
• 金额: --
• 依托单位: Arbeitsgruppe Anorganische Chemie und Strukturchemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/514566227?language=en
• 关键词: Exploration; Annulated; Phosphorus; Heterocycles; Derived

Pyrazine (1,4-diazabenzene) is an aromatic N-heterocycle and has been used extensively as a key structural component in coordination polymers and materials for optoelectronics and battery applications. In contrast, heavier analogues of pyrazine such as 1,4-diphosphinines have remained elusive species. This is due to the high propensity of these molecules to form Diels-Adler type dimers. To date, no benzannulated bi- and tricyclic heterocycles (e.g., 9,10-diphosphaanthracene) exist as monomers either. Hence, the synthetic inaccessibility of these species as monomers is a major obstacle in exploring their fundamental chemistry as well as their potential applications in materials science. To overcome this problem, we pursue the strategy of formally replacing the peripheral benzene rings of 9,10-diphosphaanthracene with 1,3-imidazole units to obtain fused tricyclic heterocycles with a central C4P2 ring. The 1,3-imidazole units have sterically demanding aryl substituents at the 1,2,3-positions. The desired starting materials Li(ADCAr), the so-called anionic dicarbenes (ADCAr = {:CN(Dipp)}2CAr; Dipp = 2,6-iPr2C6H3, Ar = aryl) developed by us, are readily accessible by the double (C4/C5) deprotonation of the corresponding C2-arylated 1,3-imidazolium salts. For example, the reaction of Li(ADCPh) with PCl3 yields [(ADCPh)PCl2]2, which after reduction with 4 equivalents of KC8 gives the 1,4-diphosphinine-1,4-diide compound [(ADCPh)P]2 with a central C4P2 ring containing 8π-electrons. The antiaromatic [(ADCPh)P]2 system can be readily oxidized with AgOTf to give the [(ADCPh)P]2(OTf)2 with a central 6π-electron aromatic C4P2-ring. Encouraged by these preliminary results on the ready accessibility of annulated phosphorus heterocycles with a central 6π- or 8π-electron C4P2-ring, we now aim to prepare new derivatives and systematically investigate their structure, reactivity, and photophysical properties. The stability and properties of the target compounds are aimed to be modified by varying the nature of the C2-substituent on the 1,3-imidazole moiety. Stable radicals will be prepared by one-electron oxidations of the corresponding C4P2-species. Reactivity studies with N2O and organic azides (RN3) aim to isolate monomeric P-heterocycles containing P=X bonds (X = O or NR; R = alkyl or aryl). The redox behavior and photophysical properties of the targeted compounds will be studied by electrochemical and spectroscopic (UV-vis absorption/ emission) studies, respectively. To gain a clear insight into the electronic structures of the target heterocycles, we will also perform quantum chemical calculations.

吡嗪（1,4-二氮杂苯）是一种芳香的n -杂环化合物，作为一种关键的结构成分被广泛应用于光电子和电池领域的配位聚合物和材料中。相比之下，更重的吡嗪类似物，如1,4-二膦，仍然是难以捉摸的物种。这是由于这些分子形成Diels-Adler型二聚体的高倾向。到目前为止，还没有苯环双环和三环杂环（例如，9,10-二磷蒽）作为单体存在。因此，这些物种作为单体的合成不可接近性是探索其基础化学及其在材料科学中的潜在应用的主要障碍。为了克服这一问题，我们采用了用1,3-咪唑单元正式取代9,10-二磷蒽外围苯环的策略，得到了具有中心C4P2环的融合三环杂环。1,3-咪唑基在1,2,3位上有要求立体的芳基取代基。所需原料Li(ADCAr)，即所谓阴离子二苯(ADCAr = {:CN(Dipp)}2CAr；Dipp = 2,6- ipr2c6h3, Ar =芳基)可以通过相应的c2芳基化1,3-咪唑盐的双（C4/C5）去质子化反应得到。例如，Li（ADCPh）与PCl3反应生成[(ADCPh)PCl2]2，与4个等量的KC8还原后得到1,4-二膦-1,4-二化合物[(ADCPh)P]2，其中心C4P2环含有8π电子。反芳香[(ADCPh)P]2体系可以很容易地与AgOTf氧化，得到具有中心6π电子芳环的[(ADCPh)P]2(OTf)2。受这些初步结果的鼓舞，我们现在的目标是制备新的衍生物，并系统地研究它们的结构、反应性和光物理性质。目的是通过改变1,3-咪唑部分上的c2取代基的性质来修饰目标化合物的稳定性和性质。通过对相应的c4p2进行单电子氧化，可以制备稳定的自由基。与N2O和有机叠氮化物（RN3）的反应性研究旨在分离含有P=X键的单体P-杂环（X = O或NR； R =烷基或芳基）。目标化合物的氧化还原行为和光物理性质将分别通过电化学和光谱（紫外-可见吸收/发射）研究。为了更清楚地了解目标杂环的电子结构，我们还将进行量子化学计算。