The title compounds (1 a) 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, (1 a) and (3a) both readily yield single photocyclomers, respectively (1 b) and (3b). Under the same experimental conditions, the photocyclomerization quantum yield of ( l a ) 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 (CH,), 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 ( l a ) (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.

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The title compound, C(19)H(15)NO(6), contains a planar isoxazole ring. An intramolecular hydrogen bond is formed between the OH group attached to a phenyl ring and a carbonyl O atom.

The structure determination of the title compound, C 22 H 20 O 4 , was undertaken in order to establish its the conformation, especially the angle between the aromatic ring system and the ethylene moiety, which turned out to be 68.06 (5)°. CommentCompounds containing an anthracene ring system show important photochemical and physical properties (Endo et al., 1997;Becker & Andersson, 1983). Intramolecular charge transfer between the anthracene moiety and attached groups has been deeply explored by absorption and emission spectra (Becker & Andersson, 1983). The title compound contains an anthracene ring system to which an ethylene bond is attached at position 9. Due to steric hindrance this ethylene bond cannot be coplanar with the aromatic ring system: the angle between the anthracene ring system and the ethylene moiety is 68.06 (5) 3 ml of TiCl 4 was pourred into 50 ml of tetrahydrofurane (THF) and was then given under continuous stirring to 2.6 g anthraldehyd previously dissolved in 7 ml THF plus 2 g e thyl malonate. 4 ml pyridine was added to the mixture, which was then stirred for 8 h. The solvant was evaporated, washed several times with water and extracted with dichloromethane. The final product was filtrated on silicae gel. The yellow crystals melt at 371 K. RefinementThe data collection nominally covered a sphere of reciprocal space, by a combination of four sets of exposures; each set had a different φ angle for the crystal and each exposure covered 0.3° in ω. The crystal-to-detector distance was 5 cm. Coverage of the unique set is over 98% complete to at least 26.5° in θ. Crystal decay was monitored by repeating the initial frames at the end of data collection and analyzing the duplicate reflections.All H atoms were located by difference Fourier synthesis and refined with fixed individual displacement parameters [U(H) = 1.5 U eq (C methyl ) or U(H) = 1.2 U eq (C)] using a riding model with C sp 2 -H = 0.95, C-H secondary = 0.98 or C-H methyl = 0.99 Å, respectively.

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