The photophysics of a structurally unique aza-analogue of polycyclic aromatic hydrocarbons characterized by 12 conjugated rings and a curved architecture is studied in detail. The combined experimental and computational investigation reveals that the lowest excited state has charge-transfer character in spite of the absence of any peripheral electron-withdrawing groups. The exceptionally electron-rich core comprised of two fused pyrrole rings is responsible for it. The observed strong solvatofluorochromism is related to symmetry breaking occurring in the emitting excited state, leading to a significant dipole moment (13.5 D) in the relaxed excited state. The anomalously small fluorescence anisotropy of this molecule, qualitatively different from what is observed in standard quadrupolar dyes, is explained as due to the presence of excited states being close in energy but having different polarization directions.
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