Kinetic scheme for intramolecular excimer formation in bis(.alpha.-naphthylmethyl)ether, involving different starting conformations

Cd2+-sensiting bichromophore: Excimer emission from an EDTA-methylnaphthalene derivative

“…1b, the spectrum of ligand 2 exhibited a weak structureless band at 391 nm together with an intense band having a structure at 335 nm at pH 9.6, at which the ligand molecule was completely deprotonated to exist as L 2À . The 335 nm band is attributable to monomeric (or isolated) naphthyl group, and the 391 nm band to naphthyl excimer by comparison with the emission spectra reported for naphthalene derivatives [1][2][3][4][5][6][7][8][13][14][15]22]. The excimer is formed as a result of an intramolecular interaction because an intermolecular interaction is not operative for naphthalene at concentration as low as 10 À6 M [13].…”

Photochemistry of polychlorinated phenoxyphenols. 2. Phototransformations of m-(pentachlorophenoxy)-2,4,5,6-tetrachlorophenol

“…The observation of C-Cl bond fission from the triplet state with very little accompanying C-0 bond fission suggests that C-Cl bond fission benefits from an electron transfer process (Ohashi et al, 1973; Bunce et al, 1975Bunce et al, , 1976Bunce et al, , 1978; Ruzo et al, 1975;Chitten et al, 1978; Davidson and Goodin, 1981; Grimshaw and deSilva, 1981; Soumillion and deWolf, 1981), while C-0 bond fission does not. If a cyclization process analogous to that considered for the cyclization of predioxin (la) (Freeman and Srivinasa, 1983) is operative, an electron transfer, perhaps intramolecular (Okajima et al, 1977;Soumillion and deWolf, 1981;Todesco et al, 1981), followed by C-Cl bond fission would provide the key intermediates on the pathway to cyclic product (eq 1). To test the susceptibility of substrate lb to electron transfer, an irradiation was carried out in the presence of sensitizer and an electron donor.…”

Intramolecular fluorescence quenching in porphyrin-bearing [2]catenates

“…The rate constants for quenching k q1 and k q2 (Table 5) While k q1 is within experimental error independent of the temperature, a decrease of k q2 upon decreasing the temperature is observed for [2] [39]. The activation energies and preexponential factor are also of the correct order of magnitude for a conformational change around a (saturated)carbonoxygen bond [40][41][42][43][44] in open-chain molecules. Hence, it is [45,46].…”