Detailed structural, magnetic, and photoluminescence (PL) characterization of four new compounds based on 1-methylimidazole-5-carboxylate (mimc) ligand and transition metal ions, namely [Ni(mimc)₂(H₂O)₄] (1), [Co(μ-mimc)₂]_n (2), {[Cu₂(μ-mimc)₄(H₂O)]·2H₂O}_n (3), and [Cd(μ-mimc)₂(H₂O)]_n (4) is reported. The structural diversity found in the family of compounds derives from the coordination versatility of the ligand, which coordinates as a terminal ligand to give a supramolecular network of monomeric entities in 1 or acts as a bridging linker to build isoreticular 2D coordination polymers (CPs) in 2–4. Magnetic direct-current (dc) susceptibility data have been measured for compounds 1–3 to analyze the exchange interactions among paramagnetic centers, which have been indeed supported by calculations based on broken symmetry (BS) and density functional theory (DFT) methodology. The temperature dependence of susceptibility and magnetization data of 2 are indicative of easy-plane anisotropy (D = +12.9 cm^–1, E = +0.5 cm^–1) that involves a bistable M_s = ±1/2 ground state. Alternating-current (ac) susceptibility curves exhibit field-induced single-ion magnet (SIM) behavior that occurs below 14 K, which is characterized by two spin relaxation processes of distinct nature: fast relaxation of single ions proceeding through multiple mechanisms (U_eff = 26 K) and a slow relaxation attributed to interactions along the polymeric crystal building. Exhaustive PL analysis of compound 4 in the solid state confirms low-temperature phosphorescent green emission consisting of radiative lifetimes in the range of 0.25–0.43 s, which explains the afterglow observed during about 1 s after the removal of the UV source. Time-dependent DFT and computational calculations to estimate phosphorescent vertical transitions have been also employed to provide an accurate description of the PL performance of this long-lasting phosphor.

中文翻译：

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用1-甲基咪唑-5-羧酸盐和过渡金属离子设计单离子磁体和磷光材料

四种基于1-甲基咪唑-5-羧酸盐（mimc）配体和过渡金属离子的新化合物，即[Ni（mimc）₂（H ₂ O）₄ ]的详细结构，磁性和光致发光（PL）表征（1） ，[Co（μ-mimc）₂ ] _n（2），{[Cu ₂（μ-mimc）₄（H ₂ O）]·2H ₂ O} _n（3）和[Cd（μ-mimc）₂（H ₂ O）] _n（4）被报告。在化合物家族中发现的结构多样性源于配体的配位多功能性，配位体作为末端配位体进行配位，以在1中提供单体实体的超分子网络，或充当桥联接头，以在其中构建等网状2D配位聚合物（CP）。2 – 4。磁直流（DC）的易感性的数据已测量了化合物1 - 3分析的顺磁中心，其中已经通过基于打破对称（BS）和密度泛函理论（DFT）计算方法已经确实支持之间的交换相互作用。磁化率和磁化强度数据的温度依赖性2表示易平面各向异性（D = +12.9 cm ^–1，E = +0.5 cm ^–1），其中涉及双稳态M _s =±1/2基态。交流（ac）磁化率曲线显示在14 K以下发生的场感应单离子磁体（SIM）行为，其特征是两个性质不同的自旋弛豫过程：单离子快速弛豫通过多种机理进行（U _eff = 26 K）和缓慢的松弛归因于沿着聚合物晶体结构的相互作用。化合物4的详尽PL分析在固态状态下，确认低温磷光绿色发射包括0.25-0.43 s的辐射寿命，这解释了在去除紫外线源后约1 s观察到的余辉。还采用了与时间有关的DFT和估算磷光垂直跃迁的计算方法来提供这种持久磷光体的PL性能的准确描述。