Desaktivierungsverhalten von Arenen und Heteroarenen. XXXVI. Zum Lösungsmittel‐ und Temperatureinfluß auf das Desaktivierungsverhalten von 9, 9′‐Bis(acridizinium‐yl) bei hohen Konzentrationen

Abstract

Deactivation Behaviour of Arenes and Heteroarenes. XXXVI. The Solvent and Temperature Dependence of Deactivation Behaviour of 9, 9′‐Bis(acridizinium‐yl) at High Concentration At room temperature the geometrical structure of the fluoresceing singlet state of 9, 9′‐bis(acridizinium‐yl) is determined by the solvent. In solvents of the type A (water, methanol, acetonitril) a plain S1‐state emits, in the case of the solvent type B (ethanol, propanol‐(2)) the S1‐state is twisted. Both excited states have different emission spectroscopical properties. At high concentration (c ≥ 10−4 mol l−1) in the case of the solvent type B a new emission band is observed, and the monomer emission is quenched. This new band is interpreted as a fluorescence from a molecular associate in the excited state. The intensity of this associate band is increasing with decreasing temperature. It is shown that this band is the result of molecular association in the ground state. From the photochemical irradiation it follows that only in the case of the solvent type B a photocycloaddition is possible. The plain S1‐state does not react.