Fig. 4. The analysis of transient absorption spectra of (a) S-TPA-PI and (b) S-2TPA-2PI in DMSO; (c) the dynamics corresponding to (a and b) for excited state absorption of isolated S-TPA-PI and S-2TPA-2PI, respective the analysis of transient absorption spectra of (d) S-TPA the and (e) S-2TPA-2PI in the H₂O; (f) the dynamics corresponding to (d and e) for excited state absorption of aggregated S-TPA-PI and S-2TPA-2PI. (g) The energy level diagrams of the isolated state, J-aggregate, and “end-to-end” stacking adopted from single crystal data based on the M06-2X functional and RI/J approximation calculations in the gas phase.