No abstract

The spectroscopy and photochemistry of brilliant green leucocyanide la were investigated at room and low temperature, in polar and nonpolar solvents. At 77 K, la exhibits solvent independent absorption, fluorescence (4,. = O.l), and phosphorescence (4, = 0.5). Solvent effects become important at room temperature; in polar solvents, 4, decreases and photodissociation yielding brilliant green dye 3 occurs [&,(EtOH) -0.91. Dye formation and la fluorescence can be quenched by 0.1 M crotononitrile. Attempts to sensitize dye formation with triplet sensitizers were unsuccessful. The spectroscopy of 3 was also examined.

A series of ring‐substituted phenyl and naphthyl azides have been prepared. Electronic absorption spectral properties and quantum yields of disappearance have been determined in aqueous solution. For phenyl azide derivatives, the wavelengths of maximum absorption vary systematically, correlating with electronic effects of the ring substituents. Quantum yield values of 0.1–0.7 are obtained and are independent of a number of experimental conditions, including concentration. There is no simple correlation of the quantum yields of azide disappearance with electronic effects, except that the naphthyl azides have higher photochemical efficiencies than the phenyl azide derivatives. A series of potential protein photolabels has been identified based on electronic absorption characteristics and photochemical efficiencies.

Abstract. –An analysis of the temperature dependence of trans‐stilbene fluorescence yield in dipalmitoyl lecithin vesicles is used to obtain activation energies. The results are interpreted in terms of bilayer fluidity through and above the phase transition. Oxygen quenching of the fluorescence of pyrenebutyric acid (incorporated in dipalmitoyl lecithin and egg lecithin vesicles) is reported as a function of temperature and bulk oxygen concentration. Above the bilayer phase transition, quenching rates (determined by oxygen quenching) decrease with decreasing temperature. A reduction in oxygen quenching is observed through the dipalmitoyl lecithin phase transition.

No abstract