Geipel G, Acker M, Vulpius D, Bernhard G, Nitsche H, Fanghänel Th
Forschungszentrum Rossendorf, Institute of Radiochemistry, P.O. Box 510119, D-01314 Dresden, Germany.
Spectrochim Acta A Mol Biomol Spectrosc. 2004 Jan;60(1-2):417-24. doi: 10.1016/s1386-1425(03)00244-0.
A dedicated spectrofluorimeter using ultrashort laser pulses as an excitation source was developed to measure the fluorescence properties of organic ligands for metal ion complexation with organic ligands. The laser system consists of an oscillator system for generation of femtosecond laser pulses, an amplifier system to increase the pulse energy of the generated pulses to about 2 mJ and an optical parametrical amplifier system to provide tunable laser pulses over a wide wavelength range (280 nm-10 microm). The laser pulses were applied to the sample and the emitted fluorescence was detected using a fast-gating intensified CCD camera-based spectrometer. To verify the performance of the laser, the well-known protonation constant [Pure Appl. Chem. 69 (1997) 329] of 2,3-dihydroxybenzoic acid was determined. The fluorescence lifetime of the excited species was determined as 375+/-32 ps in the pH range from 1.0 to 6.0, having a fluorescence emission maximum at 438 nm. The first protonation constant was determined from fluorescence data as log K(3)=3.17+/-0.05 at an ionic strength of 0.1 M and at 294 K exploiting the Stern-Volmer mechanism. The agreement of the protonation constant with literature data (log K(3)=3.10+/-0.20, I=0.1 M, T=298 K [Bull. Soc. Jpn. 44 (1971) 3459]) demonstrates the excellent performance of our system. Furthermore, we determined the complex formation constant log K(1)=-3.11+/-0.16 by measuring the fluorescence properties of the ligand for the 1:1 uranyldihydroxobenzoate complex in the pH range from 3.0 to 4.5 at ionic strength of 0.1 M and at 294 K. We also determined the complex formation constant via the fluorescence emission of the metal ion uranium(VI). The fluorescence of the uranyl ion is influenced by dynamic quenching of the non-dissociated ligand and by static quenching due to the complex formation. After correction of these effects using the determined fluorescence lifetime, the complex formation constant was calculated to be log K(1)=-3.99+/-0.44. A 1:1 metal:ligand stoichiometry was determined with both measurement methods. However, the difference of the obtained formation constants and the derived standard deviations indicate a superimposition of effects with the excited-state reactions of the ligand.
开发了一种使用超短激光脉冲作为激发源的专用荧光光谱仪，用于测量有机配体与金属离子络合时的荧光特性。该激光系统由用于产生飞秒激光脉冲的振荡器系统、将产生的脉冲能量增加到约2 mJ的放大器系统以及用于在宽波长范围（280 nm - 10微米）提供可调谐激光脉冲的光学参量放大器系统组成。将激光脉冲施加到样品上，并使用基于快速门控增强型CCD相机的光谱仪检测发射的荧光。为了验证激光的性能，测定了2,3 - 二羟基苯甲酸的著名质子化常数[《纯粹与应用化学》69 (1997) 329]。在pH值为1.0至6.0的范围内，激发态物质的荧光寿命测定为375±32 ps，在438 nm处有最大荧光发射。利用斯特恩 - 沃尔默机制，在离子强度为0.1 M和294 K的条件下，根据荧光数据确定第一个质子化常数为log K(3)=3.17±0.05。质子化常数与文献数据（log K(3)=3.10±0.20，I = 0.1 M，T = 298 K [《日本化学会通报》44 (1971) 3459]）的一致性证明了我们系统的优异性能。此外，通过在离子强度为0.1 M和294 K的条件下，在pH值为3.0至4.5的范围内测量配体与1:1铀酰二羟基苯甲酸络合物的荧光特性，我们确定了络合形成常数log K(1)= - 3.11±0.16。我们还通过金属离子铀(VI)的荧光发射确定了络合形成常数。铀酰离子的荧光受到未解离配体的动态猝灭和络合物形成导致的静态猝灭的影响。在使用测定的荧光寿命校正这些影响后，计算出络合形成常数为log K(1)= - 3.99±0.44。两种测量方法均确定金属与配体化学计量比为1:1。然而，获得的形成常数的差异和推导的标准偏差表明存在与配体激发态反应相关的叠加效应。
