Expanded Hexapyrrolohexaazacoronenes. Near-Infrared Absorbing Chromophores with Interrupted Peripheral Conjugation

A family of azacoronenes containing up to two saturated bridges at the periphery was synthesized from substituted hexapyrrolylbenzenes using a two-step condensation–aromatization procedure. The introduction of peripheral bridges provides access to nonplanar, sterically crowded systems that display complex reactivity patterns, involving stereospecific aromatization of bridges and nucleophile additions. Despite the interrupted conjugation on the periphery, the new azacoronenes have easily accessible higher oxidation levels, and a quadruply charged species was chemically generated by reaction with SbCl5. These oxidized species show extensive π-electron conjugation and are efficient UV–vis–NIR absorbers, active up to ca. 2400 nm. Interruption of peripheral conjugation is shown to induce a tendency toward biradicaloid electron configurations in doubly oxidized species.

以取代六吡咯基苯（hexapyrrolylbenzenes）为起始原料，通过两步缩合-芳构化（condensation–aromatization）反应流程，合成了外围最多带有两个饱和桥连基团的氮杂蔻烯（azacoronenes）家族化合物。外围桥连基团的引入，可获得非平面、空间位阻拥挤的分子体系，这类体系展现出复杂的反应模式，涵盖桥连基团的立体专一性芳构化以及亲核加成反应。尽管外围共轭（conjugation）被打断，但新型氮杂蔻烯具备易于实现的更高氧化态，且通过与五氯化锑（SbCl5）反应，可化学制备得到四电荷物种。这些氧化态物种具有广泛的π电子共轭特性，属于高效的紫外-可见-近红外（UV–vis–NIR）吸收材料，其吸收活性最高可达约2400 nm。研究表明，外围共轭的打断会使双氧化态物种呈现出双自由基型电子构型（biradicaloid electron configurations）的倾向。