Naphthalene chromophore

CD spectroscopy appeared highly suitable because compounds 10-12 possess two chromophores, naphthalene and r-triazine, having electrically allowed, well-characterized electronic transitions. In Figure 10 is reported the absorption and CD spectra (acetonitrile solution) of 2,4,6-tris[(7 )-l(l-naphthyl)ethylamino]-l,3,5-triazine 12 <2000EJ01767>. 

In the case of /3-styryInaphthalene, direct or sensitized excitation apparently does not involve exclusive formation of a single excited state from the two isomers.(S4) This seems reasonable in that the naphthalene and styryl moieties can act as coupled low-energy chromophores. 

Results are shown in Figure 5. Samples of PVCa were doped with 10% by weight of poly(1-vinylnaphthalene) to determine if the naphthalene chromophore would serve as a quencher for the surface oxidation of PVCa as it appears to do in the case of fluid solutions. 

The data in Figure 5 indicates that the presence of the naphthalene chromophore does not prevent the decrease in contact angle observed upon the irradiation of PVCa. Thus, naphathalene may rot be an effective quencher of the surface oxidation of PVCa film as it appears to be for the yellowing of PVCa in solution. 

All azo dyes contain one or more azo groups (-N=N-) as chromophore in the molecule on the basis of the number of azo groups in each molecule, they are named monoazo-, disazo-, trisazo-, etc. The azo groups are in general bound to a benzene or naphthalene ring, but they can also be attached to heterocyclic aromatic molecules or to enolizable aliphatic groups. On the basis of the characteristics of the processes in which they are applied, the molecule of the dye is modified to reach the best performances so they can be acid dyes, direct dyes, reactive dyes, disperse dyes, or others. 

Broadly speaking, the cavity sizes of a-, f -, and y-CD are appropriate for binding simple derivatives of benzene, naphthalene, and anthracene, respectively (Sanemasa and Akamine, 1987 Fujiki et al., 1988 Sanemasa et al., 1989). Many studies of the inclusion of aromatics, particularly of dyes and other molecules with strong chromophores, have been reported, and these have been useful in delineating the main features of CD binding (Bender and Komiyama, 1978 Saenger, 1980 Szejtli, 1982 Atwood et al., 1984 Stoddart and Zarzycki, 1988). In contrast, the affinity of small to medium aliphatic molecules for CDs have been less well studied, most... 

Fluorescein is an energy acceptor for chromophores such as naphthalene and anthracene and acts as energy donor toward Eosin and Rhodamine, so derivatives have been used for singlet-singlet energy transfer studies. According to Forster s theory [68] the rate constant for energy transfer increases... 

When the enone chromophore of the diketone (148) is excited selectively using 2537 A-light, a smooth conversion to the two stereoisomeric cyclopropyl diketones (149) and (150) takes place exclusively.27,28,44 Experiments with the 4a-deuteriomethyl analog of (148) establish a stepwise reaction sequence with the diradicals (151) [- (149)] and (152) [-> (150)] as the most likely intermediates formed in the primary photoprocess. Total quenching with naphthalene indicates the triplet nature of the reaction. 

Typical intramolecular (2 + 2) photocycloaddition of electron-rich alkenes to the 1-cyanonaphthalene ring via an exciplex has been reported by McCullough and Gilbert, independently. McCullough reported intramolecular photocycloaddition of bichromophoric molecules 255,258, and 259, in which the chromophores are linked by a three-atom ether chain [286,287] (Scheme 71). The fluorescence of the 1-cyanonaphthalene chromophore of 255,258, and 259 is efficiently quenched by alkenes and the typical intramolecular exciplex emissions are observed. Photocycloaddition of these 1-cyanonaphthalenes in benzene occurs at 1,2-, 3,4-, or 5,6-positions of the naphthalene ring, respectively. 

Intramolecular photocycloaddition of naphthalene and anthracene has been studied by Chandross and Schiebel [327], At concentrations above 10 3 M, bi-molecular photodimerization of the anthracene occurs in deaerated methylcyclo-hexane solution. In contrast, irradiation of much more dilute ( 2 X 105 M) solutions resulted in the formation of intramolecular adduct 342 (Scheme 94). Bouas-Laurent et al. showed that the CH2—O—CH2 link is more efficient than the (CH2)3 chain in bridging the two chromophores [328], Irradiation of diethyl ether or methylcyclohexane solution of 343 (5 X 10 5 M) with a high-pressure mercury lamp and liquid filter (X > 335 nm) gave a single photoadduct 344, which was isolated quantitatively. The quantum yield of 344 is 10 times higher than that of 342. 

Intramolecular Photocycloaddition of N—P4—A. Although the photocycloaddition of anthracene [85-100] and that of naphthalene [65-67,80-82] have been extensively studied, until recently relatively little has been reported on the cross-photocycloaddition between an anthracene and a naphthalene moiety [101-110], The main reason for this is the large difference in the quantum yields between the photocycloaddition of anthracene and the cross-photocycloaddition of anthracene and naphthalene. Thus, bichromophoric molecules with anthryl as one chromophore and naphthyl as the other generally undergo intermolecular an-thryl-anthryl cycloaddition rather than intramolecular cross-cycloaddition when irradiated. 

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