First, we investigated how the charge distribution in tw-HDMAPAN is affected upon excitation. The computed electrostatic potential (ESP) maps for the S0 state of tw-HDMAPAN indicate the positive charge character localized over the dibenzotropylium carbon bonded to the anilinium unit (Fig. ). Upon excitation, the positive charge is more evenly spread through the dibenzotropylium moiety; even though the positive character of C1 is reduced in the S1 state, the negative character seems to be slightly more localized to the distal side of the dibenzotropylium moiety (carbons C5 -C12), which is furthest away from the anilinium, with more positive character on the carbons C1 -C4 and C13 -C15 (i.e. a reduction of red on that region upon excitation, see plot in Fig. ). Although the changes are modest, that means the positive charge becomes more delocalized over the complete dibenzotropylium moiety upon excitation, and this remains also after relaxation to the S1 minimum structure. As seen in Fig. So, what can be the origin of the charge redistribution in the excited state? The dibenzotropylium unit has in total 14 π-electrons distributed over the three rings. Similar to its isoelectronic compound anthracene, 66 a number of different resonance structures can be drawn for dibenzotropylium, one of the cycles having a (4n + 2) π-electron Hückel-aromatic ring.