Magnetic and luminescence characteristics of dinuclear complexes of lanthanides and a phenolic schiff base macrocyclic ligand
Magnetic and luminescence characteristics of dinuclear complexes of lanthanides and a phenolic schiff base macrocyclic ligand
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DOI：
10.1016/s0020-1693(00)87513-1
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发表时间：
1988-08
影响因子：
2.8
通讯作者：
I. Kahwa;J. Selbin;C. O'connor;J. Foise;G. McPherson
中科院分区：
文献类型：
--
作者：
I. Kahwa;J. Selbin;C. O'connor;J. Foise;G. McPherson
本文研究了由2，6-二甲酰基对甲酚和三乙烯四胺合成的2：2酚盐席夫碱L与镧系同双核大环三元配合物的磁性和发光性质。Pr ~（3+）配合物的磁化率随温度的变化不符合居里-韦斯温度关系，轴向磁化率与晶场分裂和弱的双核Pr ~（3+）→ Pr ~（3+）反铁磁相互作用有关.“灰白色”Pr 2L（NO3）4·2 H2O、“黄色”Pr 2L（NO3）4和“橙子色”Pr 2L（NO3）2（OH）2的交换作用参数分别为zJ′ = −2.2、−4.4和−7.0 cm− 1。与此相反，Ln_2L（NO_3）_3（OH）配合物（Ln = Dy，Ho）的磁化率在整个温度范围内（6 K ~ 300 K）都遵循居里-外斯行为。封闭壳层离子La ~（3+）、Lu ~（3+）、Y ~（3+）和半填充壳层离子Gd ~（3+）的配合物在450 ~ 650 nm范围内有很强的配体荧光，在77 K时，Ln = Gd的衰减时间为2-4 ns，Ln = Gd的衰减时间为5-8 ns。Gd ~（3+）的配合物在600 nm处也有磷光，衰减时间约为200 μs。含Ce ~（3+）、Eu ~（3+）、Tb ~（3+）和Er ~（3+）的配合物显示出非常弱的配体发光，表明有效的猝灭过程。镧系离子的敏化发射仅在Eu ~（3+）配合物中观察到（5Do→ 7 Fj跃迁）。在纯Eu ~（3+）配合物中，发光寿命为250 μs。Eu ~（3+）在“灰白色”La_2L（NO_3）_4nH_2O中的稀释样品的发射衰减曲线显示出明显的上升时间和双相衰减（快成分约400 μs;慢成分约2500 μs）。L和Eu ~（3+）的发光态有一个共同的激发光谱，这与L的电子吸收光谱相似，表明配体-金属离子能量转移过程占主导地位。研究结果表明，配合物的光谱性质是由稀土离子与大环配体席夫碱部分的配位方式决定的。
The magnetic and luminescence characteristics of trimorphic homodinuclear macrocyclic complexes of lanthanides and a 2:2 phenolate Schiff's base L, derived from 2,6-diformyl-p-cresol and triethylenetetramine were determined. The complexes of Pr3+exhibit non-Curie-Weiss temperature dependent magnetic susceptibilities for which satisfactory fits to an axial relationship depends on crystal field splitting and a weak binuclear Pr3+Pr3+antiferromagnetic interaction. The exchange interaction parameters are zJ′ = −2.2, −4.4 and −7.0 cm−1for ‘off-white’ Pr2L(NO3)4·2H2O, ‘yellow’ Pr2L(NO3)4, and ‘orange’ Pr2L(NO3)2(OH)2, respectively. In contrast, magnetic susceptibilities of the Ln2L(NO3)3(OH) complexes (Ln = Dy, Ho) follow Curie-Weiss behavior over the entire temperature range (6 K to 300 K). The complexes of closed shell ions La3+, Lu3+, Y3+and those of the half filled shell ion Gd3+exhibit a strong ligand fluorescence in the 450 nm to 650 nm range with decay times at 77 K of 5–8 ns for Ln≠Gd or 2–4 ns for Ln = Gd. The complexes of Gd3+also exhibit a phosphorescence at 600 nm (decay time ∼ 200 μs). The complexes containing Ce3+, Eu3+, Tb3+and Er3+show very weak ligand luminescence indicative of effective quenching processes. Sensitized emission from the lanthanide ion is observed only with the Eu3+complexes (5Do→7Fjtransitions). The emission lifetimes are on the order of 250 μs in the pure Eu3+complexes. The emission decay curves from dilute samples of Eu3+in ‘off-white’ La2L(NO3)4nH2O show a noticeable rise time as well as a biphasic decay (fast component ∼ 400 μs; slow component ∼ 2500 μs). The luminescing states of L and Eu3+have a common excitation spectrum which is similar to the electronic absorption spectrum of L indicating that ligand-to-metal ion energy transfer processes are dominant. Overall the result if this study suggest that the spectral properties of the complexes are determined by the coordination mode of the lanthanide ions to the Schiff base portion of macrocyclic ligand.