Coordination complexes of precious metals with the d⁶ valence electron configuration such as Ru(II), Os(II) and Ir(III) are used for lighting applications, solar energy conversion and photocatalysis. Until now, d⁶ complexes made from abundant first-row transition metals with competitive photophysical and photochemical properties have been elusive. While previous research efforts focused mostly on Fe(II), we disclose that isoelectronic Cr(0) gives access to higher photoluminescence quantum yields and excited-state lifetimes when compared with any other first-row d⁶ metal complex reported so far. The luminescence behaviour of the metal-to-ligand charge transfer excited states of these Cr(0) complexes is competitive with Os(II) polypyridines. With these Cr(0) complexes, the metal-to-ligand charge transfer states of first-row d⁶ metal complexes become exploitable in photoredox catalysis, and benchmark chemical reductions proceed efficiently under low-energy red illumination. Here we demonstrate that appropriate molecular design strategies open up new perspectives for photophysics and photochemistry with abundant first-row d⁶ metals.

具有 d ⁶价电子构型的贵金属配位络合物，例如 Ru(II)、Os(II) 和 Ir(III)，用于照明应用、太阳能转换和光催化。到目前为止，由丰富的第一行过渡金属制成的具有竞争性光物理和光化学性质的 d ⁶配合物一直难以捉摸。虽然之前的研究工作主要集中在 Fe(II) 上，但我们发现，与迄今为止报道的任何其他第一行 d ⁶金属配合物相比，等电子 Cr(0) 可以获得更高的光致发光量子产率和激发态寿命。这些 Cr(0) 配合物的金属到配体电荷转移激发态的发光行为与 Os(II) 聚吡啶具有竞争性。有了这些 Cr(0) 配合物，第一行 d ⁶金属配合物的金属到配体的电荷转移态就可以在光氧化还原催化中利用，并且基准化学还原在低能量红色照明下有效进行。在这里，我们证明了适当的分子设计策略为具有丰富的第一排 d ⁶金属的光物理学和光化学开辟了新的视角。