Picosecond Solvation Dynamics of Coumarin153 in Bis(1-methyl-1H-imidazol-3-ium-3-yl)dihydroborate Cation Containing Room Temperature Ionic Liquid and Ionic Liquid-DMF Mixtures


  • Prabhat Kumar Sahu National Institute of Science Education and Research
  • Sudhir Kumar Das National Institute of Science Education and Research
  • Moloy Sarkar National Institute of Science Education and Research, Bhubaneswar




Ionic liquid, Time-dependent Stokes shift, Solvation dynamics, polar cosolvent, Anisotropy


Abstract: Steady state and time-resolved fluorescence behavior of coumarin153(C153) in bis(1-methyl-1H-imidazol-3-ium-3-yl)dihydroborate cation containing room temperature ionic liquid and its mixture with dimethylformamide (DMF) has been investigated. Density functional calculations on the present ionic liquid have been carried out to have ground state structural information of this system. C-H···N and C-H···O hydrogen bonding interactions between cationic and anionic moiety of the present ionic liquid has been observed. Steady state absorption and emission spectral profiles of C153 are found not to be influenced by the polar cosolvent. Time-resolved fluorescence anisotropy experiments show that the rotational motion of the probe becomes faster in presence of DMF. During time dependent dynamic Stokes shift measurements in ionic liquid-DMF mixtures, the average solvation time is found to decrease with the addition of DMF to the ionic liquid. The decrease in both average solvation and rotational time of probe molecule upon gradual addition of polar organic co-solvent is attributed to the lowering of bulk viscosity of the medium.

Author Biographies

Prabhat Kumar Sahu, National Institute of Science Education and Research

School of Chemical Sciences

Sudhir Kumar Das, National Institute of Science Education and Research

School of Chemical Sciences


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