Ground and excited state interaction between luminol and ethylene trithiocarbonate: A fluorescence quenching study

Abstract

The absorption spectral change and fluorescence quenching of luminol (3-aminophthalhydrazide) due to the interaction with ethylene trithiocarbonate (ETTC) both in the ground and excited states have been investigated using steady state and time- correlated single photon counting techniques. The complex formation in the ground state is assumed to explain the high value of bimolecular rate constant and is consistent with positive curvatures in the Stern -Volmer (S-V) plots. The equilibrium constant for the complex formation due to the hydrogen bonding interaction has been calculated from absorption spectral changes. The bimolecular rate constants in hydrogen bonding solvents have been round to be quite higher than those obtained in nonpolar and weakly polar solvents. It is proposed that interaction in the ground state is mainly between luminol and hydrogen bonding solvent molecules. A plausible explanation of the quenching mechanism has been discussed on the basis of hydrogen bonding interaction between the colliding species.