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

S0 → S1 and S0 → S2 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 S1 and S2 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 S1 state. The S2–S1 electronic energy spacing has been calculated from the absorption maxima of the S0 → S2 transitions and fluorescence maxima of the S1 → S0 transitions. Solute–solvent interactions have been established to rationalize the photophysical modification of PZ in H-bonding solvents.