PHOTOCHEMISTRY OF 1,2,3-INDANETRIONE

The photochemistry of 1,2,3-indanetrione (1) has been examined in solution at room temperature by steady state and laser flash photolysis. The triplet state of 1 (tau = 6.5-mu-s, lambda-max = 360 and 570 nm, in dry acetonitrile) reacts preferentially via an alpha-cleavage process followed by a considerably slower loss of carbon monoxide. Triplet 1 shows a remarkably fast hydrogen abstraction rate constant when in the presence of 1,4-cyclohexadiene (k(r) = 1.4 x 10(6) M-1 s-1) in spite of its low excitation energy (E(T) = 42 kcal/mol). This behavior can be explained by assuming that the vicinal carbonyls coplanar to the ketyl radical play an important role in its stabilization.