Acta Phys. -Chim. Sin. ›› 2014, Vol. 30 ›› Issue (11): 2134-2141.doi: 10.3866/PKU.WHXB201409161

• PHOTOCHEMISTRY AND RADIATION CHEMISTRY • Previous Articles     Next Articles

Primary Photochemical Properties of Difloxacin in Neutral Aqueous Solution

LI Hai-Xia1,2, ZHOU Bao-Chang1, LIU Yan-Cheng1,2, TANG Rui-Zhi1,2, ZHANG Peng1,2, LI Jing-Ye1, WANG Wen-Feng1   

  1. 1. Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201800, P. R. China;
    2. Graduate University of Chinese Academy of Sciences, Beijing 100049, P. R. China
  • Received:2014-04-10 Revised:2014-09-15 Published:2014-10-30
  • Contact: WANG Wen-Feng
  • Supported by:

    The project was supported by the National Natural Science Foundation of China (21173252).


The photochemical properties of difloxacin (DFX) were investigated in neutral aqueous solution. DFX aqueous solution showed intense absorption with one peak at 273 nm (molar absorption coefficient ε= 33000 dm3·mol-1·cm-1) and two other peaks at 323 and 335 nm (ε=15500 dm3·mol-1·cm-1) with the same molar absorption coefficient. Both the absorption and emission properties of DFX were pH-dependent. The acid dissociation constant (pKa) for the protonation equilibria of the ground state (5.9 and 9.8) were determined spectroscopically. DFX fluoresces weakly, and its maximum quantum yield for fluorescence emission was 0.06 at pH 3. Laser flash photolysis and pulse radiolysis studies were carried out to characterize the transient species of DFX aqueous solution. Triplet-triplet absorption reached a maximum at 620 nm with a molar absorption coefficient of 7900 dm3·mol-1·cm-1. The energy transfer method was used to estimate the triplet energy of DFX, which was 263.5 kJ·mol-1. The quantum yield of triplet formation was determined to be 0.21. Furthermore, DFX showed monophotonic photoionization with a quantum yield of 0.02. Pulse radiolysis indicated that DFX could react with eaq- and ·OH, and the bimolecular rate constants for these reactions were 1.72×1010 and 1.0×1010 dm3· mol-1 ·s-1, respectively. It is expected that this research may be helpful in determining the phototoxicity mechanism of DFX.

Key words: Photochemical property, Laser flash photolysis, Pulse radiolysis, Difloxacin, Excited state