N^N Pt(II) Bisacetylide Complexes with Oxoverdazyl Radical Ligands: Preparation, Photophysical Properties, and Magnetic Exchange Interaction between the Two Radical Ligands
N^N Pt(II) Bisacetylide Complexes with Oxoverdazyl Radical Ligands: Preparation, Photophysical Properties, and Magnetic Exchange Interaction between the Two Radical Ligands
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N^N Pt(II) 双乙酰化物与 Oxoverdazyl 自由基配体的配合物：制备、光物理性质以及两个自由基配体之间的磁交换相互作用
DOI：
10.1021/acs.inorgchem.0c01575
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发表时间：
2020
影响因子：
4.6
通讯作者：
Voronkova Violeta K.
中科院分区：
文献类型：
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作者：
Yang Wenbo;Sukhanov Andrei A.;Lim Jong Hyeon;Li Xiaoxin;Meng Yinshan;Zhao Jianzhang;Sun Haoling;Lee Jin Yong;Gurzadyan Gagik G.;Voronkova Violeta K.
为了研究稳定自由基对N^N双乙炔基Pt（II）磷光配合物的物理化学性质的影响以及自由基配体之间的分子内磁相互作用，我们合成了一系列含氧代咪唑自由基乙炔基配体的N^N双乙炔基Pt（II）配合物. Pt（II）中心和自旋载体之间的链接器被系统地改变，以探测自由基配体和电子物理性质之间的自旋交换相互作用的符号和大小的影响。复合物进行了研究，稳态和飞秒/纳秒瞬态吸收光谱，连续波电子顺磁共振（EPR）光谱，密度泛函理论（DFT）计算。瞬态吸收光谱研究表明，自由基的激发态是短寿命的（τD <$2 ps）和无荧光的。此外，Pt（II）配位中心的固有长寿命三重激发态（τT= 1.2 μs）被自由基有效猝灭（对于一个代表性的自由基Pt（II）络合物，τT= 6.9 ps）。用变温EPR谱研究了自由基配体之间通过抗磁性Pt（II）原子的分子内磁性相互作用;观察到具有最短自由基-自由基距离的配合物通过桥片段的反铁磁交换相互作用（− JS 1 S2，J= −5.4 ± 0.1 cm-1）。DFT计算给出了J值的符号和大小的类似结果。然而，对于具有较大自由基间距离的络合物，观察到自由基配体之间的非常弱的耦合（|J| < 0.7 cm-1）。我们的结果对于研究自由基对磷光过渡金属配合物的光物理性质的影响是有用的。
To study the effect of a stable radical on the photophysical properties of a phosphorescent Pt(II) coordination framework and the intramolecular magnetic interaction between radical ligands in the N^N Pt(II) bisacetylide complexes, we prepared a series of N^N Pt(II) bis(acetylide) complexes with oxoverdazyl radical acetylide ligands. The linker between the Pt(II) center and the spin carrier was systematically varied, to probe the effect on the sign and magnitude of the spin exchange interactions between the radical ligands and photophysical properties. The complexes were studied with steady-state and femtosecond/nanosecond transient absorption spectroscopy, continuous-wave electron paramagnetic resonance (EPR) spectroscopy, and density functional theory (DFT) computations. The transient absorption spectral studies show that the doublet excited state of the radicals are short-lived (τD≈ 2 ps) and nonfluorescent. Moreover, the intrinsic long-lived triplet excited state (τT= 1.2 μs) of the Pt(II) coordination center was efficiently quenched by the radical (τT= 6.9 ps for one representative radical Pt(II) complex). The intramolecular magnetic interaction between the radical ligands through the diamagnetic Pt(II) atom was studied with temperature-dependent EPR spectroscopy; antiferromagnetic exchange interaction (−JS1S2,J= −5.4 ± 0.1 cm–1) for the complex with the shortest radical–radical distance through bridge fragments was observed. DFT computations give similar results for the sign and magnitude of theJvalues. For complexes with larger inter-radical distance, however, very weak coupling between the radical ligands was observed (|J| < 0.7 cm–1). Our results are useful for the study of the effect of a radical on the photophysical properties of the phosphorescent transition-metal complexes.