南非约翰内斯古腾堡大学Heinze, Katja团队报道了利用近红外光氧化锰（IV）配合物的双态光活性。相关究成果发表在2024年2月8日出版的《自然—化学》。

高度还原或氧化的光催化剂是光化学中的一个基本挑战。到目前为止，只有少数与地球丰富金属离子的过渡金属配合物发展成为激发态氧化剂。所有这些光催化剂都需要高能量的光来激发，并且由于在达到光活性状态之前的能量耗散，它们的氧化能力没有得到充分利用。

该文中，研究人员证明了复合物[Mn(dgpy)₂]⁴⁺，基于地球丰富的锰和三齿2,6-二胍基吡啶配体（dgpy），在用低能近红外光激发后，进化为发光双配体到金属电荷转移（²LMCT）激发态（1435nm，0.86eV），寿命为1.6ns。这种²LMCT状态将萘氧化为其自由基阳离子。具有高达2.4V的极高氧化电位的衬底能够通过高能四重⁴LMCT激发态进行[Mn(dgpy)2]⁴⁺光还原，寿命为0.78ps，通过溶剂的静态猝灭进行。

这一过程最大限度地减少了自由能损失，并充分利用了光氧化能力，从而实现使用地球丰富的元素和低能量光氧化腈和苯。

附：英文原文

Title: Oxidative two-state photoreactivity of a manganese(IV) complex using near-infrared light

Author: East, Nathan R., Naumann, Robert, Frster, Christoph, Ramanan, Charusheela, Diezemann, Gregor, Heinze, Katja

Issue&Volume: 2024-02-08

Abstract: Highly reducing or oxidizing photocatalysts are a fundamental challenge in photochemistry. Only a few transition metal complexes with Earth-abundant metal ions have so far advanced to excited state oxidants. All these photocatalysts require high-energy light for excitation, and their oxidizing power has not been fully exploited due to energy dissipation before reaching the photoactive state. Here we demonstrate that the complex [Mn(dgpy)2]4+, based on Earth-abundant manganese and the tridentate 2,6-diguanidylpyridine ligand (dgpy), evolves to a luminescent doublet ligand-to-metal charge transfer (2LMCT) excited state (1,435nm, 0.86eV) with a lifetime of 1.6ns after excitation with low-energy near-infrared light. This 2LMCT state oxidizes naphthalene to its radical cation. Substrates with extremely high oxidation potentials up to 2.4V enable the [Mn(dgpy)2]4+ photoreduction via a high-energy quartet 4LMCT excited state with a lifetime of 0.78ps, proceeding via static quenching by the solvent. This process minimizes free energy losses and harnesses the full photooxidizing power, and thus allows oxidation of nitriles and benzene using Earth-abundant elements and low-energy light.

DOI: 10.1038/s41557-024-01446-8

Source: https://www.nature.com/articles/s41557-024-01446-8