N. C. Yang

THE PHOTOCHEMICAL REACTIONS OF 1,3–DIMETHYLURACIL WITH 1–AMINOPROPANE AND POLY-l-LYSINE†

Abstract— Irradiation of 1,3–dimethyluracil (DMU) in 1–aminopropane (AP) with u.v. light resulted in the formation of reduced and dimeric forms of DMU and adducts between DMU and AP. The formation of these compounds may be rationalized from the activation of either DMU or AP. Irradiation of DMU and poly‐l‐lysine in water with u.v. light resulted in the extensive binding of DMU to poly‐l‐lysine. The pyrimidine is probably attached to the ε‐carbon of the polypeptide at the 6–position. The biological implications of these studies are discussed.

Radiationless decay processes in 2-naphthaldehyde

Abstract The deuteration of the aldehydic C-H in 2-naphthaldehyde exerts a marked effect on the non-radiative process while the deuteration on all of the seven aromatic C-Hs exerts a far less pronounced effect. The results are discussed in connection with the vibrational structures of the phosphorescence emissions from 2-naphthaldehyde and deuterated 2-naphthaldehyde.

Photochemistry and photophysics of 1,4-dewarnaphthalene

Abstract Photoexcited 1,4-dewarnaphthalene (1) rearranges in high efficiency to excited naphthalene in both the singlet and the triplet manifold. Assuming the relative efficiencies of fluorescence to intersystem crossing of 1 are similar to those of substituted benzenes, the rearrangement of triplet 1 to triplet naphthalene may be adiabatic. The relative efficiencies of fluorescence to rearrangement to singlet excited naphthalene from singlet excited 1 at 77 K depends on the wavelength of exciting light, the shorter the wavelength, the more efficient the rearrangement.

Effect of viscosity on fluorescence of anthracenes in solution

The fluorescence quantum yields of 9‐alkylated anthracenes vary appreciably with solvent viscosity at 22 °C, while those of anthracene and 9,10‐dimethyl‐anthracene do not. The increase in fluorescence quantum yield in a more viscous solvent is due to a decrease in the rate of nonradiative decay. (AIP)

Photorearrangement of photocycloadducts from arenes and 1,3-cyclohexadiene

Abstract The 4π s +π s photoadduct from an arene and 1,3-cyclohexadiene may undergo a photochemical rearrangement to the 4π s +π s adduct.