Role of homogeneous solvents on photophysics of 3-pyrazolyl-2-pyrazoline derivative

S-0 - S-1 and S-0 -> S-2 electronic transitions have been observed in UV-Visible absorption spectroscopy of 3-pyrazolyl-2-pyrazoline (PZ) in different homogeneous solvents. Radiative emissions and relaxation processes from S-1 and S-2 states of PZ have been resolved in water, ethylene glycol and glycerol whereas in polar aprotic and protic solvents the radiative transitions have been observed from S-1 state. The S-2-S-1 electronic energy spacing has been calculated from the absorption maxima of the S-0 -> S-2 transitions and fluorescence maxima of the S-1 -> S-0 transitions. Solute-solvent interactions have been established to rationalize the photophysical modification of PZ in H-bonding solvents. (c) 2007 Elsevier B.V. All rights reserved.