電子移動光化学反応

抄録

Usual photochemical reactions occur from either directly light-absorbed molecules (direct photoreaction) or exothermic energy transfered molecules (sensitized photoreaction). Recently, many new examples of the third photoreaction [electron transfer (ET) photoreaction] have been published. The ET photoreaction involving the excited state electron transfer from an electron donating compound (D) to an electron accepting compound (A) normally proceeds via an exciplex (excited state charge transfer complex) or a solvated radical ion pair (D⁺_.·A^-_.), and is quite important because it has opened the possibility of "formal endothermic sensitization." Usual ET photoreactions can be classified into four types concerning product (P) formation ; type 1 (D+A→P), type 2 (D+A→P+D), type 3 (D+A→P+A), and type 4 [(D…A]_CT→P]. This article explains the above four types of ET photoreactions using examples mainly developed in this laboratory ; photo-Friedel-Crafts reaction, photocyclization of imide, photohydrolysis of sulfonamide, photocleavage of water, oxidative cleavage of aromatic ring, and strained cage formation as a light energy conversion model.