Nanosecond Metal-to-Ligand Charge-Transfer State in an Fe(II) Chromophore: Lifetime Enhancement via Nested Potentials
Nanosecond Metal-to-Ligand Charge-Transfer State in an Fe(II) Chromophore: Lifetime Enhancement via Nested Potentials
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Fe(II) 发色团中的纳秒金属到配体的电荷转移状态：通过嵌套电势延长寿命
DOI：
10.1021/jacs.2c13532
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发表时间：
2023
影响因子：
15
通讯作者：
Vura-Weis, Josh
中科院分区：
文献类型：
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作者：
Malme, Justin T.;Clendening, Reese A.;Ash, Ryan;Curry, Taylor;Ren, Tong;Vura-Weis, Josh
具有长寿命(≥1 ns)电荷转移态的Fe络合物的例子仅限于具有强σ给体螯合物的伪八面体几何结构。基于不同配位基序和配体配基的替代策略是非常可取的。本文报道了一种空气稳定的四方FeII络合物，Fe(HMTi)(CN)2(HMTi=5，5，7，12，12，14-hexamethyl-1，4，8，11-tetraazacyclotetradeca-1，3，8，10-tetraene)，)，具有1.25 ns的金属-配体电荷转移寿命。确定了它的结构，并研究了它在各种溶剂中的光物理性质。HMTi配体是高度π酸性的，这是由于低位π*(C═N)，它通过稳定t2 Gorbitals来增强ΔFe2。大环的刚性几何结构导致了短的Fe-N键，密度泛函理论计算表明，这种刚性导致了一组不寻常的嵌套势能面。此外，MLCT态的寿命和能量强烈依赖于溶剂环境。这种依赖性是由于溶剂和氰基配体之间的Lewis酸碱相互作用对轴向配体-场强度的调制造成的。这项工作代表了FeI大环物种中长寿命电荷转移状态的第一个例子。
Examples of Fe complexes with long-lived (≥1 ns) charge-transfer states are limited to pseudo-octahedral geometries with strong σ-donor chelates. Alternative strategies based on varying both coordination motifs and ligand donicity are highly desirable. Reported herein is an air-stable, tetragonal FeIIcomplex, Fe(HMTI)(CN)2(HMTI = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-1,3,8,10-tetraene), with a 1.25 ns metal-to-ligand charge-transfer (MLCT) lifetime. The structure has been determined, and the photophysical properties have been examined in a variety of solvents. The HMTI ligand is highly π-acidic due to low-lying π*(C═N), which enhances ΔFevia stabilizing t2gorbitals. The inflexible geometry of the macrocycle results in short Fe–N bonds, and density functional theory calculations show that this rigidity results in an unusual set of nested potential energy surfaces. Moreover, the lifetime and energy of the MLCT state depends strongly on the solvent environment. This dependence is caused by modulation of the axial ligand-field strength by Lewis acid–base interactions between the solvent and the cyano ligands. This work represents the first example of a long-lived charge transfer state in an FeIImacrocyclic species.