Light-Induced Small Molecule Fixation by Diradicals

能量的化学储存构成了一个巨大的挑战，并意味着强键的转化，如N2，CO2等，更弱的债券。理想情况下，根据光化学方法的蓝图，太阳的能量直接用于以连续的方式裂解这些键（“光活化”）。这一领域大多数方法的共同特点是过渡金属，因为需要控制将能源“分割”成较小的“能源包”。然而，近年来在具有过渡金属活性和小前线轨道能隙等电子结构的低价主族化合物领域取得了很大进展。调查的动力是用地球上丰富的、对环境无害的元素替代稀有和有毒金属。具有非常小的HOMO-LUMO能隙或甚至三重态基态的分子（例如分子氧）被称为双自由基（类）。在他们的隔离方面取得了巨大进展。然而，双自由基的键活化化学很少被探索。尽管它们的电子结构与过渡金属和双氧类似，但它们的光致反应性，除了瞬态双自由基状态和并苯之外，仍然是甚至未知的领域。在这个项目中，我们将证明，仅基于地球丰富元素的双自由基，“拟金属”化合物可以光化学激活小分子，如二氮，并将其转化为增值产品。

The chemical storage of energy constitutes a grand challenge and implies the transformation of strong bonds, as in N2, CO2, etc., to weaker bonds. Ideally and in accordance with the blueprints of photochemical approaches, the sun’s energy is directly used to cleave these bonds (“photoactivation”) in a sequential manner. Common feature of most approaches in this field are transition metals due to the requirement to control “partitioning” of energy into smaller “energy packages”. However, recent years brought much progress in the field of low-valent main-group compounds with transition metal-like reactivity and electronic structures such as small frontier orbital energy gaps. Investigations are driven by the incentives to substitute rare and toxic metals with earth-abundant and environmentally benign elements. Molecules with exceedingly small HOMO–LUMO energy gaps or even a triplet ground state such as dioxygen are referred to as diradical(oid)s. Tremendous progress has been made in their isolation. Yet, the bond activation chemistry of diradicals has rarely been explored. Despite the analogy of their electronic structure with transition metals and dioxygen, their photoinduced reactivity, beyond transient diradical states and acenes, remains even unchartered territory. Within this project, we will demonstrate that diradicaloid, “metallomimetic” compounds based only on earth-abundant elements may photochemically activate small molecules such as dinitrogen, and convert them into value-added products.