Photochemistry and excited state prototropic behaviour of 8-amino 2-naphthol.

In the present work, photophysical behaviour of 8-amino 2-naphthol in various solvents as well as at various pH values has been investigated. Various ground and excited state species are noticed. It exhibits a completely different photo prototropic behaviour as compared to its parent molecule 2-naphthol. The spectral and transient studies indicate that at lower pH values, equilibrium between cation and neutral exists in the excited state. At neutral pH some peculiar behaviour in its spectral properties is noticed.

Steady state and time-resolved fluorescence study of isoquinoline: reinvestigation of excited state proton transfer.

In the present work we report some hitherto unnoticed features in the steady state and time-resolved measurements of isoquinoline in water and trifluoroethanol (TFE). Absorption spectra reveal that in water, neutrals as well cationic species are present. Emission spectrum shows structured features at shorter wavelengths accompanied with a broad band around 375 nm, which correspond to neutrals and cations respectively. However, time-resolved data indicate that protonation does not take place in the excited state in water. On the contrary, in stronger hydrogen bonding solvent TFE, distribution of decay components is observed and at longer wavelengths a small rise time is present. This is ascribed to neutral and cation-like species present in the ground as well as in the excited state. The difference in the results is explained in terms of different excited state potential energy surfaces for water and TFE; particularly, the presence of a rather small barrier for protonation in case of TFE.