<br>Pd(II) 和 Pt(II) 配合物作为超分子发光体的室温磷光：自组装、金属-金属相互作用、自旋轨道耦合和配体场分裂的作用,Journal of the American Chemical Society

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Pd(II) 和 Pt(II) 配合物作为超分子发光体的室温磷光：自组装、金属-金属相互作用、自旋轨道耦合和配体场分裂的作用
Journal of the American Chemical Society ( IF 14.4 ) Pub Date : 2023-02-13 , DOI: 10.1021/jacs.2c09775
Tobias Theiss _{1,

2} , Stefan Buss _{1,

2} , Iván Maisuls _{1,

2} , Rafael López-Arteaga ₃ , Dana Brünink ₄ , Jutta Kösters ₁ , Alexander Hepp ₁ , Nikos L Doltsinis ₄ , Emily A Weiss ₃ , Cristian A Strassert _{1,

2}

Affiliation

报道了两种等配双环金属化 Pt(II) 和 Pd(II) 配合物（即 [ PtL ] 和 [ PdL ]）的合成以及结构和光物理表征，它们带有定制的双阴离子四齿配体（ L ^2– ）。通过核磁共振波谱和 X 射线衍射分析评估了 [ PtL ] 和 [ PdL ] 的同构特征和分子间相互作用。两种配合物均显示出完全由配体控制的聚集，表明明智的分子设计可以调整光物理性质。事实上，通过在指定位置引入氟原子和在互补位点引入甲氧基，可以通过头尾堆叠来强制金属-金属相互作用。因此，[ PtL ]在稀释溶液、冷冻玻璃和晶体中显示出来自金属扰动的配体中心或来自金属-金属-配体电荷转移三重态的发光，具有高光致发光量子产率和微秒级的长寿命范围。在室温 (RT) 的浓缩流体溶液中，钯类似物 [ PdL ] 令人惊讶地从涉及超分子相互作用的聚集物质中发出发光。时间分辨光致发光和瞬态吸收光谱表明，两种金属都会发生超快系间窜越，这超出了光激发单线态的任何竞争性弛豫途径。此外，我们证明，在 77 K 的冷冻玻璃基质中以及在室温下流体溶液中的分子间相互作用可以抑制无辐射失活。在这两种情况下，正如密度泛函理论计算所示，最低发射态充当能量陷阱，正式占据反键 Pd 中心 4d _{x ²} _{– y ²}轨道的解离态热布居被抑制。当发射态和暗态之间的能隙超过kT时，就会发生这种情况。

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Room-Temperature Phosphorescence from Pd(II) and Pt(II) Complexes as Supramolecular Luminophores: The Role of Self-Assembly, Metal–Metal Interactions, Spin–Orbit Coupling, and Ligand-Field Splitting

The synthesis as well as the structural and photophysical characterization of two isoleptic bis-cyclometalated Pt(II) and Pd(II) complexes, namely [PtL] and [PdL], bearing a tailored dianionic tetradentate ligand (L^2–) are reported. The isostructural character and intermolecular interactions of [PtL] and [PdL] were assessed by NMR spectroscopy and X-ray diffraction analysis. Both complexes show fully ligand-controlled aggregation, demonstrating that a judicious molecular design can tune the photophysical properties. In fact, by introduction of fluorine atoms on defined positions and methoxy groups on complementary sites, metal–metal interactions can be forced by a head-to-tail stacking. Hence, [PtL] shows luminescence from metal-perturbed ligand-centered or from metal-metal-to-ligand charge-transfer triplet states in diluted solutions, in frozen glasses and in crystals, with high photoluminescence quantum yields and long lifetimes in the microsecond range. At room temperature (RT) in concentrated fluid solutions, the palladium analogue [PdL] surprisingly emits luminescence from aggregated species involving supramolecular interactions. Time-resolved photoluminescence and transient absorption spectroscopies demonstrated that ultrafast intersystem crossing occurs for both metals, which outruns any competitive relaxation pathway from the photoexcited singlet state. Furthermore, we demonstrate that the radiationless deactivation can be suppressed in frozen glassy matrices at 77 K and by intermolecular interactions in fluid solutions at RT. In both cases and as indicated by density functional theory calculations, the lowest emissive state acts as an energy trap from which the thermal population of dissociative states with formal occupation of an antibonding Pd-centered 4d_x²_–y² orbital is suppressed. This occurs as the energy gap between the emissive and the dark states surpasses kT.

更新日期：2023-02-13

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