Interestingly, we show that the modulation of the acceptor group leads to a very different nonradiative relaxation of the excited states. Indeed, while the presence of the oxo group favors E→Z isomerization, its replacement by malonitrile block the isomerization and therefore much largely activates vibrational relaxation, leading to increased photothermal conversion. The reasons behind switch in the non-radiative decay balance of the two compounds is also rationalized by the study of the potential energy surface (PES) landscape through molecular modeling and simulation at multiconfigurational wave-function level. In addition, when the donor group is strengthened (from ether to amine), both photothermal conversion efficiency and fluorescence build up, opening ways for theranostic approaches.