A new series of gallium(III)/lanthanide(III) metallacrown (MC) complexes (Ln-1) was synthesized by the direct reaction of salicylhydroxamic acid (H₃shi) with Ga^III and Ln^III nitrates in a CH₃OH/pyridine mixture. X-ray single crystal analysis revealed two types of structures depending on whether the nitrate counterion coordinate or not to the Ln^III: [LnGa₄(shi)₄(H₂shi)₂(py)₄(NO₃)](py)₂ (Ln = Gd^III, Tb^III, Dy^III, Ho^III) and [LnGa₄(shi)₄(H₂shi)₂(py)₅](NO₃)(py) (Ln = Er^III, Tm^III, Yb^III). The representative Tb-1 and Yb-1 MCs consist of a Tb/YbGa₄ core with four [Ga^III–N–O] repeating units forming a non-planar ring that coordinates the central Ln^III through the oxygen atoms of the four shi³⁻ groups. Two H₂shi⁻ groups bridge the Ln^III to the Ga^III ring ions. The Yb^III in Yb-1 is eight-coordinated while the ligation of the nine-coordinated Tb^III in Tb-1 is completed by one chelating nitrate ion. Ln-1 complexes in the solid state showed characteristic sharp f–f transitions in the visible (Tb, Dy) and near-infrared (Dy, Ho, Er, Yb) spectral ranges upon excitation into the ligand-centered electronic levels at 350 nm. Observed luminescence lifetimes and absolute quantum yields were collected and discussed. For Yb-1, luminescence data were also acquired in CH₃OH and CD₃OD solutions and a more extensive analysis of photophysical properties was performed. This work demonstrates that while obtaining highly luminescent lanthanide(III) MCs via a direct synthesis is feasible, many factors such as molar absorptivities, triplet state energies, non-radiative deactivations through vibronic coupling with overtones of O–H, N–H, and C–H oscillators and crystal packing will strongly contribute to the luminescent properties and should be carefully considered.

中文翻译：

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具有非平面[12-MC-4]核的GaIII / LnIII金属腔的晶体结构和光物理性质的奇特性

一系列新的镓（III）/镧系元素（III）metallacrown（MC）复合物（LN-1 ）通过水杨酸的直接反应，合成（H ₃ SHI）随镓^III和LN ^III在CH硝酸盐₃ OH /吡啶混合物。X射线单晶分析显示出两种类型的结构，这取决于硝酸盐抗衡离子是否与Ln ^III协调：[LnGa ₄（shi）₄（H ₂ shi）₂（py）₄（NO ₃）]（py）₂（Ln = Gd ^III，Tb ^III，Dy ^III，Ho ^III）和[LnGa ₄（shi）₄（H ₂ shi）₂（py）₅ ]（NO ₃）（py）（Ln = Er ^III，Tm ^III，Yb ^III）。代表性的Tb-1和Yb-1 MC由一个Tb / YbGa ₄核和四个[Ga ^III –N–O]重复单元组成，形成一个非平面环，该环通过四个shi的氧原子协调中心Ln ^{III 3}组。两个H _2个市^-组弥合LN ^III到Ga ^III环离子 镱^III中的Yb-1是八配位，而九协调Tb的结扎^III在TB-1是由一个硝酸螯合离子完成。固态Ln-1配合物在激发到350 nm处以配体为中心的电子能级时，在可见光谱（Tb，Dy）和近红外光谱（Dy，Ho，Er，Yb）的光谱范围内表现出明显的f–f跃迁。收集并讨论了观察到的发光寿命和绝对量子产率。对于Yb-1，还获得了CH ₃ OH和CD _3中的发光数据进行了OD溶液和光物理性质的更广泛的分析。这项工作表明，虽然可以通过直接合成获得高发光度的镧系元素（III）MC ，但许多因素，例如摩尔吸收率，三重态能量，通过振动耦合的O–H，NH–和H泛音的非辐射失活等。 C–H振荡器和晶体堆积将极大地促进发光性能，应仔细考虑。