Kamil Witas, Shruthi Santhosh Nair, Tamar Maisuradze, Linda Zedler, Heiner Schmidt, Pablo Garcia-Porta, Alexandra Stefanie Jessica Rein, Tim Bolter, Sven Rau, Stephan Kupfer, Benjamin Dietzek-Ivanšić, Dieter U Sorsche
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引用次数: 0
摘要
分子过渡金属发色团在光收集和能量转换方面发挥着核心作用。最近,基于富土过渡金属的发色团开始挑战铂族金属复合物在这一领域的主导地位。然而,具有优化光物理特性的新型发色团的开发仍然受限于合成方法的缺乏,尤其是带有功能配体的异质络合物。在这里,我们展示了一种简便、高效的方法,将强场碳烯与功能性 2,2'-联苯并咪唑配体结合成异性发色铁(II)配合物。我们的方法产生了两种异构体,根据配体场的对称性,它们的激发态寿命主要不同。这两种异构体的去质子化会导致金属-配体电荷转移(MLCT)吸收的显著红移和激发态寿命的缩短。飞秒瞬态吸收光谱与量子化学模拟和共振拉曼光谱相结合,揭示了质子化与光物理特性之间的复杂关系。研究发现,质子化会使 MLCT 和金属中心激发态(MC)之间的平衡向前者倾斜。这项研究首次展示了通过第二球操作微调铁(II)发色团激发态景观的实例,为 3d 过渡金属发色团激发态优化的挑战提供了一个新的视角。
Beyond the First Coordination Sphere─Manipulating the Excited-State Landscape in Iron(II) Chromophores with Protons.
Molecular transition metal chromophores play a central role in light harvesting and energy conversion. Recently, earth-abundant transition-metal-based chromophores have begun to challenge the dominance of platinum group metal complexes in this area. However, the development of new chromophores with optimized photophysical properties is still limited by a lack of synthetic methods, especially with respect to heteroleptic complexes with functional ligands. Here, we demonstrate a facile and efficient method for the combination of strong-field carbenes with the functional 2,2'-bibenzimidazole ligand in a heteroleptic iron(II) chromophore complex. Our approach yields two isomers that differ predominantly in their excited-state lifetimes based on the symmetry of the ligand field. Deprotonation of both isomers leads to a significant red-shift of the metal-to-ligand charge transfer (MLCT) absorption and a shortening of excited-state lifetimes. Femtosecond transient absorption spectroscopy in combination with quantum chemical simulations and resonance Raman spectroscopy reveals the complex relationship between protonation and photophysical properties. Protonation is found to tip the balance between MLCT and metal-centered (MC) excited states in favor of the former. This study showcases the first example of fine-tuning of the excited-state landscape in an iron(II) chromophore through second-sphere manipulations and provides a new perspective to the challenge of excited-state optimizations in 3d transition metal chromophores.
期刊介绍:
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