Regulatory principles, parameters and probe design to ascertain the interconnection between ICT, ESIPT and PET mechanisms.

• This review will be helpful to the young readers regarding mechanistic approach and the elaborate discussion. • The learning aspect of the photophysical processes such as ICT, PET and ESIPT phenomena with their correlation and interconnection among these probable processes. • It is to establish the actual mechanistic path responsible for the observe phenomena in the fluorophore. • Controlling or tuning of the phophysical process (s) should be carried out varying the substituent for changing the structural properties in different solvent media of different solvent environments. A lot of work has been done on PET, ICT and ESIPT individually as well as following triple mechanism simultaneously. Even, in many reported works only ICT or PET mechanism has been considered although there remains a possibility of ESIPT and vice-versa. To know/predict the actual mechanistic pathway, we need to have the detailed experimental as well as theoretical characteristic data. There is some unique difference among ESIPT, ICT and PET mechanisms. If we clearly observe the structure of the probe, and the UV–vis, fluorescence spectral data as well as solvent dependency, then only we can accurately predict the operative mechanism. Sometimes, there may be a possibility of coupled or triplicate mechanism simultaneously involved in a particular condition or a single mechanism dominates over others in a probe system. Hence, this review will be helpful in assisting the young readers regarding the prediction of the mechanistic approach evaluating the exact pathway responsible for photophysical changes. [ABSTRACT FROM AUTHOR]