Photocycloaddition of .beta.-methylstyrenes to some 9-cyanophenanthrenes. Chemical Consequences of exciplex formation

Charge-transfer quenching of singlet excited complexes

“…The analogous equations ( 8) and (9) follow obviously when Q2 is added. Note that >(M) in ( 8) and ( 9) is not the same as '(M)°i n ( 6) and ( 7), since Q2 can in principle (and often does) quench 'M and since exciplex quenching by Q2 will affect the amount of reversion (¿mci…”

Photocopolymerizations of electron-rich olefins with electron-poor olefins by irradiation of their EDA complexes

“…4 Similarly, Vlasov et al prepared symmetric polypeptide chains containing photolabile disulfide or azo groups which on photolysis in the presence of several vinyl monomers produce polypeptide-polyvinyl block polymers. 5 In the present paper photochemical block polymerization was based on the incorporation of p,p -dihydroxybenzoin methyl ether groups (BME) in poly(bisphenol A carbonate). Its photolysis in the absence and presence of vinyl monomers as well as the formation of polycarbonate-polyvinyl block polymers will be considered successively.…”

Photocycloaddition of Some Difluoro(aminoenonato)boron Complexes with Arylalkenes

“…The photoaddition of furan to 1-naphthonitrile also gives a [4 4] cycloadduct with an anti-configuration, but that of 2-naphthonitrile occurs in the syn-direction to produce a cage-like compound [15]. These data suggest that the flexibility of the structure of the exciplexes may be due to the role that dipoleÀdipole interactions, the polarity, and the crowding of the exciplex play in the orientation of cycloaddition [16].…”

“…iv) In some [2 2] photoadducts, a retro-aldol reaction occurs, producing the 1,5-diketones. Some of these phenomena (i) ± iii)) may be readily interpreted by assuming the presence of an adduct (intermediate) such as the B-complex 1/arylalkene 2 complex, i.e., as an exciplex [7] [8] produced via a photoinitiated electron-transfer reaction. The difluoroboron complex is known to possess a lower reduction potential than that of the parent didentate ligand [9], and those of 1a ± c are lower by 0.4 ± 0.5 V. The oxidation and reduction potentials of the B-complexes 1a ± c, the parent didentate ligands 1a' ± c', and the arylalkenes 2a ± d are summarized in Tables 5 and 6.…”

“…However, in most singlet-state reactions, the configuration of the olefins is retained in the cycloadduct [8]. In other words, the major products (ca.…”