The interactions of the one-electron oxidants, N 3 • and Br 2 •radicals, with serotonin, tryptamine and their analogues 5-methoxytryptamine, N-methyltryptamine and N(1)-methyltryptophan were studied using the technique of pulse radiolysis with spectrophotometric detection. One-electron oxidation of serotonin results in the formation of an indoloxyl radical with a pK a value ,3. With tryptamine, N-methyltryptamine and 5-methoxytryptamine, their one-electron oxidation gives indolyl radicals with pK a values of 4.2, 4.3 and 4.8, respectively. The reactions of OH radicals ( • OH) with serotonin and tryptamine lead to the formation of the respective • OH-adducts, which decay by acid catalyzed water elimination to give almost quantitatively the corresponding indoloxyl and indolyl radicals, respectively. The first-order rate constants determined for water elimination are pH dependent, suggesting that the dehydration reaction is acid and base catalyzed. The • OHadduct of serotonin reacts with oxygen in competition with the dehydration reaction to yield a peroxyl radical adduct, which is tentatively suggested to eliminate HO 2 • . On the basis of the above findings, the mechanisms for the • OH -induced formation of the indoloxyl and indolyl radicals from serotonin and tryptamine respectively are proposed.

The red and orange emitters (ANA-1-3) consisting of a 4-amino-1,8-naphthalic anhydride group were synthesized. The lowest absorption band of these ANA molecules centered at approximately 450 nm is assigned to be a charge-transfer transition with emission at 514-536 nm in nonpolar solvents such as n-hexane and at approximately 590-640 nm in polar solvents such as THF and CH(2)Cl(2) and in the solid states. Emission lifetimes are measured with time-correlated single photon counting. Shorter lifetimes are observed for the ANA molecules when dissolved in polar solvents compared with those in nonpolar solvents. Strong dipole-dipole interaction of ANA molecules with solvents is indicated. At high concentrations the measured emission lifetimes, generally shortened from self-quenching, are found to remain about the same order of magnitude in ANAs. This implies that the exciton states of aggregates are formed and they exhibit a relatively long lifetime. Crystallographic data of 4-(phenyl antracen-9-yl) (ANA-2) and 4-(phenyl-2-naphthyl) amino-1,8-naphthalic anhydrides (ANA-3) show that the molecules exist as dimeric structures with antiparallel head-to-tail stacking of naphthalic anhydride planes in addition to other pi-pi stacking. The strong dipole-dipole interactions and the pi-pi stacking account for the observed red-shifted emissions of ANAs in the powders. For films prepared from vacuum sublimation, a structure similar to that in the crystal but with less crystalline order is expected based on the emission wavelength. Several electroluminescent devices based on these ANAs are reported here; they emit orange-red light at 602-628 nm with high brightness and steady external quantum efficiency.

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