Spectroscopic Properties of Fluoroquinolone Antibiotics and Nanosecond Solvation Dynamics in Aerosol-OT Reverse Micelles

Abstract

Among fluoroquinolone antibiotics, ofloxacin (OFL) and norfloxacin (NOR) have piperazinyl groups but flumequine (FLU) does not have this substitutent. The emission spectra of OFL and NOR are strong, broad structureless bands with large Stokes' shifts in water but the emission intensities are very weak in organic solvents. Thus we find that these compounds exist as different chemical species in various solvents. A continuous red shift in the emission bands for OFL and NOR is observed as the water concentration within the aerosol-OT (AOT; sodium 1,4-bis[2-ethylhexyl]sulfosuccinate) micelle increases or temperature of this solution rises. From the fluorescence anisotropy measurements of OFL and NOR, we assume the intramolecular charge transfer after excitation from the nitrogen of the piperazinyl group to the keto oxygen. Theoretical calculations further support this observation. Multifrequency phase and modulation experiments and time-resolved emission spectra clearly show the occurrence of intramolecular charge transfer and the subsequent nanosecond water reorganization around OFL or NOR in the AOT micelle. Upon increasing the water concentration within the AOT micelle, the relaxation rate increases because of the large amount of free water. The emission spectra of FLU do not exhibit any significant response to the physical properties of their environment.

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Study of pH‐dependent fluorescent property of fluoroquinolone antibiotics

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Synthesis and properties of a new green water‐soluble polymer for proton and metal‐cation sensing

“…With its intrinsic fluorescence, norfloxacin (NF) has been widely studied for its photophysical and photochemical properties because of intramolecular electron transfer from the nitrogen on the piperazinyl ring to the aromatic fluoroquilinone system 7–10…”