Intrazeolite photochemistry .18. Detection of radical cations of amine dimers upon amine photosensitization with acetophenone in the zeolite NaY

Laser flash photolysis (308-nm) of acetophenone (AcP)-aliphatic amine mixtures in the cavities of NaY zeolite generates AcP triplets, ketyl radical and dimers of amine radical cations. In contrast, photolysis of the same AcP-amine system in acetonitrile-water allows to detect exclusively AcP triplets and AcP-*. In the zeolite cavities amine radical cation appear to interact with a second neutral amine to afford the dimer radical cation detected as a longer-lived species absorbing from 480 to 580-nm. These radical cations of amine dimers have never been observed in solution except for special cyclic diamines having two nitrogen atoms rigidly held in close proximity. Product studies have revealed the formation of hydrazines in the photosensitized AcP-triethylamine irradiation adsorbed in NaY, but not in acetonitrile solution. (C) 1997 Elsevier Science Ltd.