Comparative analysis of lanthanide excited state quenching by electronic energy and electron transfer processes.
Comparative analysis of lanthanide excited state quenching by electronic energy and electron transfer processes.
复制标题
电子能量和电子转移过程对镧系元素激发态猝灭的比较分析。
DOI：
10.1039/d1fd00059d
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发表时间：
2022
影响因子：
3.4
通讯作者：
Parker D
中科院分区：
文献类型：
--
作者：
Parker D
比较了结构相关的Eu（III）配合物对电子和能量传递猝灭的相对敏感性。在两组基于1,4,7-三氮杂环壬烷的9配位配合物中，随着共轭敏化基团数量和未结合配体N原子数量的增加，Eu发射寿命减小，这与光诱导电子转移到受N质子化抑制的激发Eu（III）离子一致。铕5D0激发态的猝灭也可以通过电子能量转移来实现，具有最佳光谱重叠的菁菁染料对多种9-配位配合物的猝灭可以通过高效的FRET过程实现，该过程由Förster半径（R0）值为68 Å定义，并以109 M−1 s−1的二阶速率常数为特征；这些值对配体结构和整体络合物亲水性的变化不敏感。通过能量转移到Mn（II）和Cu（II）水离子，Eu和Tb激发态的猝灭发生在更短的距离内，速率常数约为106 M−1 s−1，这是由于光谱重叠积分低得多。在前一种情况下，计算的R0值估计在2.5到4 Å之间，表明存在需要更紧密接触的Dexter能量传递机制，这与配体提供的镧系离子的空间屏蔽程度对猝灭速率的增强灵敏度一致。
The relative sensitivities of structurally related Eu(III) complexes to quenching by electron and energy transfer processes have been compared. In two sets of 9-coordinate complexes based on 1,4,7-triazacyclononane, the Eu emission lifetime decreased as the number of conjugated sensitising groups and the number of unbound ligand N atoms increased, consistent with photoinduced electron transfer to the excited Eu(III) ion that is suppressed by N-protonation. Quenching of the Eu 5D0 excited state may also occur by electronic energy transfer, and the quenching of a variety of 9-coordinate complexes by a cyanine dye with optimal spectral overlap occurs by an efficient FRET process, defined by a Förster radius (R0) value of 68 Å and characterised by second rate constants in the order of 109 M−1 s−1; these values were insensitive to changes in the ligand structure and to the overall complex hydrophilicity. Quenching of the Eu and Tb excited states by energy transfer to Mn(II) and Cu(II) aqua ions occurred over much shorter distances, with rate constants of around 106 M−1 s−1, owing to the much lower spectral overlap integral. The calculated R0 values were estimated to be between 2.5 to 4 Å in the former case, suggesting the presence of a Dexter energy transfer mechanism that requires much closer contact, consistent with the enhanced sensitivity of the rate of quenching to the degree of steric shielding of the lanthanide ion provided by the ligand.