Chemistry Department, Faculty of Science, Suez Canal University, Ismailia, Egypt.
J Fluoresc. 2012 May;22(3):971-92. doi: 10.1007/s10895-011-1036-7.
The luminescence arising from lanthanide cations offers several advantages over organic fluorescent molecules: sharp, distinctive emission bands allow for easy resolution between multiple lanthanide signals; long emission lifetimes (μs -ms) make them excellent candidates for time-resolved measurements; and high resistance to photo bleaching allow for long or repeated experiments. A method is presented for determination of nucleosides using the effect of enhancement of fluorescence of the easily accessible europium(III)-TNB in presence of different nucleosides. The latter coordinates to Eu(III) -TNB and enhances its luminescence intensity as a result of the displacement of water from the inner coordination sphere of the central metal. A similar method for the determination of DNA based on the quenching of Eu(III)-TNB has been established. The interaction of Eu(III)-4,4,4 trifluoro-1-(2-naphthyl)1,3-butanedione (TNB) complex with nucleosides (NS) (guanosine, adenosine, cytidine, inosine) and DNA has been studied using normal and time-resolved luminescence techniques. Binding constants were determined at 293 K, 298 K, 303 K, 308 K and 313 K by using Benesi-Hildebrand equation. A thermodynamic analysis showed that the reaction is spontaneous with ΔG being negative. The enthalpy ΔH and the entropy ΔS of reactions were all determined. The formation of binary and ternary complexes of Eu(III) with nucleosides and TNB has been studied potentiometrically at (25.0 ± 0.1) °C and ionic strength I = 0.1 mol.dm(-3) (KNO3) . The formation of the 1:1 binary and 1:1:1 ternary complexes are inferred from the corresponding titration curves. Initial estimates of the formation constants of the resulting species and the protonation constants of the different ligands used have been refined with the HYPERQUAD computer program. Electrochemical investigations for the systems under investigations have been carried out using cyclic voltammetry (CV), differential pulse polarography (DPP), and square wave voltammetry (SWV) on a glassy carbon electrode in I = 0.1 mol/L p-toluenesulfonate as supporting electrolyte.
镧系阳离子的发光具有几个优点，超过有机荧光分子：尖锐，独特的发射带可以很容易地分辨多个镧系信号之间的区别; 长发射寿命（μs-ms）使它们成为时间分辨测量的理想选择; 并且对光漂白的高抗性允许进行长时间或重复的实验。提出了一种使用易接近的铕（III）-TNB 在存在不同核苷的情况下增强荧光的效应来测定核苷的方法。后者与 Eu（III）-TNB 配位，并由于中心金属的内配位球中水分子的取代而增强其发光强度。已经建立了基于 Eu（III）-TNB 猝灭的测定 DNA 的类似方法。使用正常和时间分辨发光技术研究了 Eu（III）-4,4,4 三氟-1-（2-萘基）1,3-丁二酮（TNB）与核苷（NS）（鸟苷，腺苷，胞苷，肌苷）和 DNA 的相互作用。在 293 K，298 K，303 K，308 K 和 313 K 下使用 Benesi-Hildebrand 方程确定结合常数。热力学分析表明反应是自发的，ΔG 为负值。还确定了反应的焓 ΔH 和熵 ΔS。通过电位法在（25.0±0.1）°C 和离子强度 I = 0.1 mol.dm（-3）（KNO3）下研究了 Eu（III）与核苷和 TNB 的二元和三元配合物的形成。从相应的滴定曲线推断出 1:1 二元和 1:1:1 三元配合物的形成。使用 HYPERQUAD 计算机程序对所得物种的形成常数和所用不同配体的质子化常数进行了初步估计。使用循环伏安法（CV），差分脉冲极谱法（DPP）和方波伏安法（SWV）在玻碳电极上对所研究的体系进行了电化学研究，在 0.1 mol/L p-甲苯磺酸盐作为支持电解质。
