苯酚和苯胺类化合物对鲁米诺电致化学发光的增强和抑制作用

系统研究了不同pH下的NaHCO₃-Na₂CO₃和NaOH缓冲介质中, 36种苯酚和苯胺类化合物对鲁米诺电致化学发光(Electrochemiluminescence, ECL)体系的影响. 发现苯酚和苯胺类化合物的抑制和增强作用与化合物的结构、氧化电位和介质的pH有直接的关系: 具有较高氧化电位的苯酚和苯胺类化合物对鲁米诺的ECL没有影响; 而具有较低的氧化电位、苯环上有两个处于对位的-OH(或-NH₂)或苯环上有多个相邻的-OH的化合物, 在较低的pH下有增强作用, 在较高的pH下具有抑制作用; 其它的化合物则呈现抑制作用, 抑制作用的大小与化合物的结构有关. 通过研究化合物的氧化半峰电位、ECL光谱、荧光光谱等, 提出了增强和抑制作用的可能机理: 各种有机物的电氧化产物如醌、酮及具有醌、酮结构的聚合物等能够淬灭激发态3-氨基邻苯二甲酸根阴离子(3-AP^2－*)的发射, 导致了鲁米诺的ECL的降低; 同时, 反应过程中生成的半醌自由基中间体或 会促进鲁米诺的发光反应, 呈现增强作用.

Enhancement and Inhibition by Phenols and Anilines on Luminol Electrochemiluminescence

The effect of 36 phenols and anilines on typical luminol electrochemiluminescence (ECL) was systematically investigated under different pH in NaHCO₃-Na₂CO₃ and NaOH media. It was found that the enhancement and inhibition by phenols and anilines on the luminol ECL were related to the half-peak potential, the structures of the compounds and the pH of the medium. The compounds with higher half-peak potential did not influence the ECL. The compounds with lower half-peak potential and with —OH, —NH₂ on the para-position of the benzene ring, or with three adjacent —OH on the benzene ring showed enhancing effect at lower pH and inhibiting effect at higher pH. The other compounds showed inhibiting effect and the magnitude was related to the structure of the compounds. The half-peak potential of the tested compounds, the fluorescence and the ECL spectra of the system were studied. The mechanism for ECL inhibition and enhancement has been proposed. It is likely that energy transferring from the excited state 3-aminophthalate to the quinone or ketone or their polymer formed by electro-oxidation of phenols and anilines led to the inhibiting effect and the benzosemiquinone radical and produced during the reactions were responsible for the ECL enhancement.