To better understand the quenching mechanism and turn-on mechanism, density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations were carried out on MBTPA-Tz and its post-iEDDA reaction compound MBTPA-Pz in single molecule and aggregate states. We focused on these molecules considering MBTPA-Pz's long emission wavelength and high IAC/IBC, which is ideal for biological applications. A comprehensive explanation of the assignment process for individual excited states can be found in section 3 of Supporting Information.