Kumar Satendra, Maji S, Sundararajan K
Materials Chemistry and Metal Fuel Cycle Group, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102, India.
Homi Bhabha National Institute, Training School Complex, Anushaktinagar, Mumbai 400 094, India.
Dalton Trans. 2022 Jun 27;51(25):9803-9817. doi: 10.1039/d2dt00849a.
Complex formation between uranyl and carboxylate ligands (benzoate, nicotinate and isonicotinate) has been studied extensively by absorption and luminescence spectroscopy in acetonitrile medium. Experimental data had indicated the existence of stable and enhanced luminescent tris(carboxylato) uranyl(VI) complexes [UO(L)] with symmetry. The high luminescence of these complexes was due to the sensitization of the O → U ligand to metal charge transfer (LMCT) emission by extremely intense equatorial (carboxylate ligands) LMCT bands. The variation in the experimentally observed parameters such as intensity of equatorial LMCT bands, luminescence lifetimes, quantum yields and structural parameters among tris(carboxylato) uranyl(VI) complexes are affirmed by quantum chemical calculations using density functional theory and the computational results are found to be in good agreement with experimental findings. Interestingly, in a very dilute mixture of [UO(L)] and Eu(III), energy transfer from uranyl to Eu(III) is observed and it leads to the detection of europium at trace levels. This is an intriguing observation as none of the previous studies have reported such a low level of detection limit of Eu(III) by means of energy transfer from any metal.
在乙腈介质中，通过吸收光谱和发光光谱对铀酰与羧酸盐配体（苯甲酸酯、烟酸酯和异烟酸酯）之间的配合物形成进行了广泛研究。实验数据表明存在具有对称性的稳定且增强发光的三（羧基）铀酰（VI）配合物[UO(L)]。这些配合物的高发光归因于赤道面（羧酸盐配体）极强的配体到金属电荷转移（LMCT）带对O→U配体到金属电荷转移（LMCT）发射的敏化作用。通过使用密度泛函理论的量子化学计算证实了三（羧基）铀酰（VI）配合物之间实验观察到的参数变化，如赤道面LMCT带的强度、发光寿命、量子产率和结构参数，并且计算结果与实验结果高度吻合。有趣的是，在[UO(L)]和Eu(III)的非常稀的混合物中，观察到了从铀酰到Eu(III)的能量转移，这导致了痕量水平铕的检测。这是一个有趣的观察结果，因为之前的研究均未报道过通过任何金属的能量转移实现如此低水平的Eu(III)检测限。
