Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (4): 745-752.doi: 10.3866/PKU.WHXB201402101

• PHOTOCHEMISTRY AND RADIATION CHEMISTRY • Previous Articles     Next Articles

Twofold Influence of Nitro Substituent on Aromatic Ring for Photoluminescence Properties of Benzoic Acid-Functionalized Polystyrene and Eu(Ⅲ) Complexes

XU Ze-Qing, GAO Bao-Jiao, HOU Xiao-Dong   

  1. Department of Chemical Engineering, North University of China, Taiyuan 030051, P. R. China
  • Received:2013-10-14 Revised:2014-01-25 Published:2014-03-31
  • Contact: GAO Bao-Jiao E-mail:gaobaojiao@126.com
  • Supported by:

    The project was supported by the Natural Science Foundation of Shanxi Province, China (201002100843).

Abstract:

Nitrobenzoic acid (NBA) was bound to the side chains of polystyrene (PS) to give nitrobenzoic acidfunctionalized polystyrene (PS-NBA). By a coordination reaction of PS-NBA and a Eu3+ ion, a binary polymerrare earth complex PS-(NBA)3-Eu(Ⅲ) was prepared. Additionally, with phenanthroline (Phen) as a small molecular ligand, the ternary polymer-rare earth complex PS-(NBA)3-Eu(Ⅲ)-Phen1 was also prepared. In this work, the influence of the nitro-substituted aromatic ring on the photoluminescence properties of the polymerrare earth complexes of benzoic acid (BA)-functionalized polystyrene and a Eu3+ ion were studied. The experimental results show that the nitro-substituted benzene ring had a twofold influence on the photoluminescence properties of the polymer-rare earth complexes of the benzoic acid-functionalized polystyrene and the Eu(Ⅲ) ion. Upon an intraligand charge transfer (ILCT), the nitro substituent causes the excitation energy of the BA ligand to dissipate and causes the triplet state energy of the BA ligand to decrease. As a result, the match between the lowest triplet level of the NBA ligand and the resonance energy level of the Eu(Ⅲ) ion improved significantly. The NBA ligand strongly sensitized the florescence emission of the Eu(Ⅲ) ion leading to the PS-(NBA)3-Eu(Ⅲ) and PS-(NBA)3-Eu(Ⅲ)-Phen1 complexes producing strong florescence emission, which shows the positive effect of the nitro-substituted benzene ring on the luminescence properties of the complexes. However, even though the solution of the complex was dilute the florescence emissions of the complexes weakened with an increase in the concentration of the complexes from 4.0×10-4 to 4.0×10-6 mol·L-4. This was caused by fluorescence resonance energy transfer (FRET) in which the fluorescence resonance energy of the excited complex was transferred to the nitro group as an‘acceptor’species. This indicates a negative effect of the nitro substituent on the benzene ring on the luminescence properties of the complexes.

Key words: Nitro substituent, Polymer-rare earth complex, Intraligand charge transfer, Fluorescence resonance energy transfer, Twofold influence

MSC2000: 

  • O631