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 S 1 to the T 1 level of I.