Die Photochemie von Diazo-dibenzoylmethan Eine wellenlängen- und temperaturabhängige Photoreaktion

Diazo-dibenzoylmethane I undergoes two primary photochemical processes leading to α-phenyl-α-benzoyl-methane II and dibenzoylmethane III. The formation of II is related to the lowest excited singlet state of I and the formation of III is related to the lowest excited triplet state of I. The quantum yields of both processes (Φ_II, Φ_III) are strongly wavelength dependent. It is unambiguously demonstrated, that the population of the two excited states depends on the energy of the exciting light, thus causing a wavelength effect. There is shown to be an activation barrier controlling the rate of intersystem crossing from the S₁ to the T₁ level of I.