Sinha Narayan, Wellauer Joël, Maisuradze Tamar, Prescimone Alessandro, Kupfer Stephan, Wenger Oliver S
Department of Chemistry, University of Basel, St. Johanns-Ring 19, 4056 Basel, Switzerland.
School of Chemical Sciences, Indian Institute of Technology Mandi, Mandi 175075, Himachal Pradesh, India.
J Am Chem Soc. 2024 Apr 17;146(15):10418-10431. doi: 10.1021/jacs.3c13925. Epub 2024 Apr 8.
Light-triggered dissociation of ligands forms the basis for many compounds of interest for photoactivated chemotherapy (PACT), in which medicinally active substances are released or "uncaged" from metal complexes upon illumination. Photoinduced ligand dissociation is usually irreversible, and many recent studies performed in the context of PACT focused on ruthenium(II) polypyridines and related heavy metal complexes. Herein, we report a first-row transition metal complex, in which photoinduced dissociation and spontaneous recoordination of a ligand unit occurs. Two scorpionate-type tridentate chelates provide an overall six-coordinate arylisocyanide environment for chromium(0). Photoexcitation causes decoordination of one of these six ligating units and coordination of a solvent molecule, at least in tetrahydrofuran and 1,4-dioxane solvents, but far less in toluene, and below detection limit in cyclohexane. Transient UV-vis absorption spectroscopy and quantum chemical simulations point to photoinduced ligand dissociation directly from an excited metal-to-ligand charge-transfer state. Owing to the tridentate chelate design and the substitution lability of the first-row transition metal, recoordination of the photodissociated arylisocyanide ligand unit can occur spontaneously on a millisecond time scale. This work provides insight into possible self-healing mechanisms counteracting unwanted photodegradation processes and seems furthermore relevant in the contexts of photoswitching and (photo)chemical information storage.
光触发配体解离是许多光活化化疗（PACT）相关化合物的基础，在光活化化疗中，药用活性物质在光照下从金属配合物中释放或“解笼”。光诱导配体解离通常是不可逆的，最近许多在PACT背景下进行的研究集中在钌（II）多吡啶和相关重金属配合物上。在此，我们报道了一种第一行过渡金属配合物，其中发生了配体单元的光诱导解离和自发再配位。两个蝎形三齿螯合物为铬（0）提供了一个整体六配位的芳基异氰化物环境。光激发导致这六个配位单元中的一个解配位，并与一个溶剂分子配位，至少在四氢呋喃和1,4 - 二氧六环溶剂中如此，但在甲苯中程度要小得多，在环己烷中则低于检测限。瞬态紫外 - 可见吸收光谱和量子化学模拟表明，光诱导配体解离直接源于激发态的金属到配体电荷转移态。由于三齿螯合物的设计以及第一行过渡金属的取代不稳定性，光解离的芳基异氰化物配体单元可以在毫秒时间尺度上自发地再配位。这项工作为抵消不需要的光降解过程的可能自愈机制提供了见解，并且在光开关和（光）化学信息存储方面似乎也具有相关性。
