Study of non-conjugated bichromophoric systems. Part 3. The photocyclomerization of 9-(1-naphthylmethoxymethyl)anthracene and 9-(2-furylmethoxymethyl)anthracene. Interest of the CH2–O–CH2 link

Abstract

The title compounds (1a) and (3a), easily synthesized by the Williamson method, were prepared in order to study the photophysical and photochemical interactions of anthracene and, respectively, naphthalene and furan at high dilution. By irradiation, (1a) and (3a) both readily yield single photocyclomers, respectively (1b) and (3b). Under the same experimental conditions, the photocyclomerization quantum yield of (1a) is ten times higher than that of 1-(9-anthryl)-3-(1-naphthyl)propane (2a). This shows that the CH₂–O–CH₂ link is more efficient than the (CH₂)₃ chain in bringing together the two reacting terminal groups during the excited state lifetime. The fluorescence of the bichromophores was studied under photostationary conditions and a transient kinetic analysis was performed by single photon counting. It allowed the determination of the rate parameters of a kinetic scheme where the exciplexes of (1a)(emitting) and (3a)(non-emitting) are postulated as intermediates. These kinetic results, compared with others, are discussed in terms of influence of the chromophores, chain, and medium on the intramolecular reactions.