Molecular Mechanism of the Solid‐State Fluorescence Behavior of the Organic Pigment Yellow 101 and Its Derivatives

Close and yet fluorescent: Derivatives of Pigment Yellow 101 can exhibit small intermolecular distances in the solid-state crystal structures. Nevertheless, these compounds show strong solid-state fluorescence. X-ray structure determinations and elaborate quantum-chemical calculations indicate that the unexpected fluorescence is a property of the individual molecules which is retained in the crystal. (Excited state energies are plotted along a CNN bending mode.)