Upon excitation, the dibenzotropylium unit could become influenced by Baird-antiaromaticity, and this antiaromaticity may be localized, as was observed for T1 state anthracene where the antiaromaticity localizes to the central hexagon. The computed values of the multicenter index (MCI) of tw-HDMAPAN confirm the aromatic character in the S0 states. Upon excitation, the MCI values further indicate loss of aromaticity in all rings in the dibenzotropylium moiety (Fig. ), even though the largest change in MCI occurs in the 7-member ring, which experience almost a 3-fold decrease of the MCI value in the vertical transition of S0 → S1. The normalized MCI 1/n value of the 7-member ring in the relaxed S1 state is 0.472 (where n is the number of carbons in the ring), which is close to the normalized MCI 1/n of the relaxed S1 state of benzene (0.395). Upon geometry relaxation, there is a small decrease of the MCI values in 7-member ring, and a small increase of the MCI of the flanking benzene rings (i.e. they relieve some antiaromaticity). A further and larger increase of MCI values for the flanking benzene rings is observed in the S1 state of tw-DMAPAN (Fig. ), i.e. the deprotonation is followed by a clear antiaromaticity relief. Computed aromatic fluctuation index (FLU) also agrees with the MCI values (Fig. ). Interestingly, the MCI values for the T1 state of tw-HDMAPAN also show a Baird-antiaromatic dibenzotropylium unit (Fig. ), and the computed 𝑝𝐾 𝑎 ℎ𝑣 at the T1 state also points to photoacidic character (𝑝𝐾 𝑎 ℎ𝑣 = -14, in the T1 state). The fact that the T1 state also exhibits photoacidic character is potentially very useful as the longer lifetime of this state, as compared to the S1 state, provides for a higher concentration of the photoacid in its acidic form. Design of HDMAPAN derivatives with high intersystem crossing probabilities should therefore be an interesting path for future development. Therefore, to release the excited state antiaromaticity, the dibenzotropylium moiety undergoes a change in the distribution of its electron density, and smears out the positive charge. This results in an inverse of the positive charges in the side closest to the anilinium ring. In other words, we argue that, upon excitation to the S1 state, there is a development of a positive charge in the dibenzotropylium unit approaching the anilinium ring, and this increases the electrostatic repulsion between that moiety and the acidic H-atom, making it more prone to leave as a proton, giving the compound an increased acidity in the S1 state. Considering that the charge rearrangement in Fig. could seem too subtle, we tested our hypothesis with two further computational experiments.