2D chain layer versus 1D chain: rigid aromatic benzoate disassembling flexible alicyclic dicarboxylate-based lanthanide coordination polymers with enhanced photoluminescence and characteristic single-molecule magnet behavior,CrystEngComm

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2D chain layer versus 1D chain: rigid aromatic benzoate disassembling flexible alicyclic dicarboxylate-based lanthanide coordination polymers with enhanced photoluminescence and characteristic single-molecule magnet behavior
CrystEngComm ( IF 2.6 ) Pub Date : 2020-06-03 , DOI: 10.1039/d0ce00583e
Jia-Yin Wang _{1,

2,

3,

4} , Yang Shi _{1,

2,

3,

4} , Dong-Liang Tao _{4,

5,

6,

7} , Guo-Yin Yin _{8,

9,

10,

11} , Qi-Bing Bo _{1,

2,

3,

4}

Affiliation

Aiming to study the photoluminescence and magnetic evolution by modulating the coordination environment, two series of lanthanide coordination polymers (LCPs) [Ln₂(μ₃-cpdc)₃(H₂O)₃]_n (cpdc-Ln) and [Ln(μ₃-cpdc)(μ₂-bc)(H₂O)]_n (cpdc-bc-Ln) (Ln = Eu, Tb and Dy; cpdc = cis-1,2-cyclopropane dicarboxylate; bc = benzoate) have been successfully synthesized and structurally characterized for the first time. Almost identical synthetic conditions confirm that terminal grafting of an aromatic benzoate activator on cpdc-Ln promotes disassembly of their 2D chain layer structures into isolated 1D chain motifs present in cpdc-bc-Ln. Besides the structural response, the responsive photoluminescence and magnetic evolution of cpdc-Ln and cpdc-bc-Ln are also comparatively discussed. The solid state photoluminescence properties of cpdc-Ln and cpdc-bc-Ln (Ln = Eu, Tb and Dy) are comparatively investigated under direct and sensitized excitation conditions. Since the rigid aromatic benzoate activator can play the role of an antenna and sensitize the luminescence of lanthanide ions, the excitation and emission spectra, fluorescence lifetime and absolute quantum yield results show that cpdc-bc-Ln have highly efficient photoluminescence compared with the corresponding cpdc-Ln. In particular, the absolute quantum yield for cpdc-bc-Tb is close to 100% upon excitation at 287 nm, suggesting completely effective energy transfer from benzoate to Tb³⁺ centers. Possible luminescence mechanisms concerning energy transfer are also proposed. Magnetic studies reveal the ferromagnetic coupling existing in cpdc-Dy and cpdc-bc-Dy, and only cpdc-bc-Dy with discrete 1D chain characteristics displays noticeable frequency dependence of magnetic susceptibilities and presents obvious out-of-phase signals under a 2 kOe dc field, indicating the field-induced single molecule magnet (SMM) behavior with an energy barrier of 55.07 K. The studies demonstrate that the synthetic strategy of terminal grafting aromatic groups on alicyclic multicarboxylate-based LCPs can be used to design functional materials with highly efficient photoluminescence and characteristic SMM behavior.

中文翻译：

2D链层与1D链：硬质芳族苯甲酸酯可分解基于脂环族二羧酸盐的镧系配位聚合物，具有增强的光致发光和独特的单分子磁性能

针对通过调制配位环境，两个系列的镧系元素配位聚合物（LCP）的[LN来研究光致发光和磁性进化₂（μ ₃ -cpdc）₃（H ₂ O）₃ ] _Ñ（CPDC-LN）和[LN（ μ ₃ -cpdc）（μ ₂ -bc）（H ₂ O）] _ñ（CPDC-BC-LN）（Ln为铕，铽和Dy; CPDC =顺-1,2-环丙烷二羧酸二乙酯; BC =苯甲酸酯）具有首次成功合成并进行了结构表征。几乎相同的合成条件证实了芳族苯甲酸酯活化剂的最终接枝在cpdc-Ln促进将其2D链层结构分解为cpdc-bc-Ln中存在的孤立的1D链基序。除了结构响应外，还比较讨论了cpdc-Ln和cpdc-bc-Ln的响应光致发光和磁演化。在直接和敏化激发条件下，比较研究了cpdc-Ln和cpdc-bc-Ln（Ln = Eu，Tb和Dy）的固态光致发光特性。由于硬质芳族苯甲酸酯活化剂可以起到天线的作用，并能敏化镧系元素离子的发光，因此激发和发射光谱，荧光寿命和绝对量子产率表明，cpdc-bc-Ln与相应的cpdc-Ln相比，具有高效率的光致发光。特别是，在287 nm激发时，cpdc-bc-Tb的绝对量子产率接近100％，表明从苯甲酸酯到Tb ³⁺中心的能量转移完全有效。还提出了与能量传递有关的可能的发光机理。磁性研究表明cpdc-Dy和cpdc-bc-Dy中仅存在cpdc-bc-Dy的铁磁耦合具有离散1D链特性的传感器显示了明显的磁化率频率依赖性，并且在2 kOe dc磁场下呈现出明显的异相信号，表明磁场诱导的单分子磁体（SMM）行为的能垒为55.07K。证明了在脂环族多羧酸酯基LCP上末端接枝芳族基团的合成策略可用于设计具有高效光致发光和特征SMM行为的功能材料。

更新日期：2020-07-06

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