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 (ΦII, ΦIII) 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.