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    • Keywords


      Ketocyanine dye; excited state dynamics; S2-fluoroscence; photoisomerization; solvent reorganization.

    • Abstract


      Relaxation dynamics of the excited singlet states of 2,5-bis-(N-methyl-N-1,3-propdienylaniline)-cyclopentanone (MPAC), a ketocyanine dye, have been investigated using steady-state absorption and emission as well as femtosecond time-resolved absorption spectroscopic techniques. Following photoexcitation using 400 nm light, the molecule is excited to the S2 state, which is fluorescent in rigid matrices at 77 K. S2 state is nearly non-fluorescent in solution and has a very short lifetime ($0.5 \pm 0.2$ ps). In polar aprotic solvents, the S1 state follows a complex multi-exponential relaxation dynamics consisting of torsional motion of the donor groups, solvent re-organization as well as photoisomerization processes. However, in alcoholic solvents, solvent re-organization via intermolecular hydrogen-bonding interaction is the only relaxation process observed in the S1 state. In trifluoroethanol, a strong hydrogen bonding solvent, conversion of the non-hydrogen-bonded form, which is formed following photoexcitation, to the hydrogen-bonded complex has been clearly evident in the relaxation process of the S1 state.

    • Author Affiliations


      Jahur A Mondal1 Sandeep Verma1 Hirendra N Ghosh1 Dipak K Palit1

      1. Radiation and Photochemistry Division, Bhabha Atomic Research Centre, Mumbai 400 085
    • Dates

  • Journal of Chemical Sciences | News

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