用变温红外光谱法和荧光光谱法研究了聚乙烯吡咯烷酮与苯磺酸铕的相互作用。 聚乙烯吡咯烷酮的酰胺基团可与苯磺酸铕中的铕离子发生络合配位作用, 导致聚乙烯吡咯烷酮的酰胺Ⅰ带发生红移。 这种络合配位作用, 使原本不溶于氯仿的苯磺酸铕可溶于含聚乙烯吡咯烷酮的氯仿溶液。 在苯磺酸铕固体的发射光谱中, 只能观察到铕离子的f—f跃迁特征发射峰, 而在苯磺酸铕浓水溶液的荧光光谱中, 亦可观测到苯磺酸根的π*→π跃迁峰, 说明苯磺酸铕在水溶液中存在解络合现象。 苯磺酸铕在溶液中的解络合行为使铕离子周围的可配位空间增大, 这为PVP的酰胺基团与铕离子发生络合配位作用创造了条件。

The interaction between polyvinylpyrrolidone (abbreviated as PVP) and europium benzenesulfonate was investigated by using temperature-dependent FTIR and fluorescence spectra. Europium compounds show strong coordination ability with amide groups of PVP. In order to remove the undesired H—O—H scissoring bands from the adsorbed water in FTIR spectra, temperature-dependent FTIR was utilized to reveal the spectral behavior of amide Ⅰ band after being coordinated with europium ions from europium compounds. As a result, the bond order of the carbonyl groups decreased, leading to a red-shift of amide Ⅰ band in the FTIR spectra. Furthermore, fluorescence spectra demonstrate that the interaction between PVP and europium benzenesulfonate enhanced the solubility of europium benzenesulfonate in chloroform. As a matter of fact, europium benzenesulfonate, which is insoluble in chloroform, becomes soluble in chloroform containing 10 Wt% PVP. In the fluorescence spectrum of europium benzenesulfonate crystals, only the f—f transition peaks of europium ions can be found. However, the emission peak of the π*—π transition of benzenesulfonate group appears in concentrated aqueous solution of europium benzenesulfonate. The phenomenon shows that part of benzenesulfonate undergoes decomplexation from europium benzenesulfonate complex and isolated benzenesulfonate occurs in the aqueous solution. Energy transfer pathway from excited triplet state of benzenesulfonate to europium ions is blocked in isolated benzenesulfonate. As a result, π*—π transition band of benzenesulfonate can be observed in the florescence spectrum. The decomplexation provides larger coordination space around europium ions, which favors the coordination between europium benzenesulfonate and PVP.