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Ultrafast Photodynamics of an Azopyridine-Functionalized Iron(II) Complex: Implications for the Concept of Ligand-Driven Light-Induced Spin Change
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2019-09-26 , DOI: 10.1021/acs.jpclett.9b02083
Sebastian Megow 1 , Henrike-Leonie Fitschen 2 , Felix Tuczek 2 , Friedrich Temps 1
Affiliation  

We report on the ultrafast photodynamics of an iron(II) complex with a photoisomerizable pentadentate azo-tetrapyridylamino ligand after irradiation with ultraviolet light. The results of femtosecond transient electronic absorption spectroscopy performed on the low-spin (LS) form of the title complex show that initial excitation of the ππ* state of the azopyridine unit in the ligand at λpump = 312 nm is followed by an ultrafast intersystem crossing (ISC) that leads to the formation of a metal-centered (MC) 5T state, in competition with the intended photoswitching of the azopyridine unit. Additional measurements carried out upon excitation of the singlet metal-to-ligand charge-transfer (1MLCT) transition at λpump = 455 nm suggest that this energy transfer occurs via an MLCT state. The resulting high-spin (HS) 5T state of the complex is metastable and recovers to the LS ground state with a time constant of ∼3 ns. The implications of these observations on the ligand-driven light-induced spin change concept are discussed.

中文翻译:

偶氮吡啶官能化的铁(II)配合物的超快光动力学:配体驱动的光诱导自旋变化的概念的含义。

我们在紫外线照射后报告了铁(II)与具有光致异构化的五齿偶氮-四吡啶基氨基配体的铁(II)配合物的超快光动力学。飞秒瞬态电子吸收光谱的结果在低自旋进行的标题配合物显示(LS)形式的ππ的初始激励*在λ配体的azopyridine单元的状态= 312nm的后跟一个超快间交叉(ISC)导致形成以金属为中心(MC)的5 T状态,与偶氮吡啶单元的预期光开关竞争。在λ激发单重态金属到配体的电荷转移(1 MLCT)跃迁后进行的其他测量= 455 nm表明这种能量转移是通过MLCT状态发生的。复合物的高自旋(HS)5 T状态是亚稳态的,并以约3 ns的时间常数恢复到LS基态。讨论了这些观察结果对配体驱动的光诱导自旋变化概念的影响。
更新日期:2019-09-26
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