Reduction of isoviolanthrone by reaction with photogenerated radicals.

The properties of isoviolanthrone (V(1)) and its corresponding dihydro form (V(1)-H(2)) in argon-saturated 1-phenylethanol in the presence of acetophenone were examined by photophysical and photochemical methods. Upon photolysis of the sensitizer, a radical-induced reduction of V(1) to V(1)-H(2) occurs. The quantum yield of this reduction is close to unity.

Downstream Fabry-Perot interferometer for acoustic wave monitoring in photoacoustic tomography.

An optical detection setup consisting of a focused laser beam fed into a downstream Fabry-Perot interferometer (FPI) for demodulation of acoustically generated optical phase variations is investigated for its applicability in photoacoustic tomography. The device measures the time derivative of acoustic signals integrated along the beam. Compared to a setup where the detection beam is part of a Mach-Zehnder interferometer, the signal-to-noise ratio of the FPI is lower, but the image quality of the two devices is similar.

Properties of 16,17-disubstituted dihydroviolanthrones formed by reaction of violanthrones with photogenerated radicals.

The photophysical and photochemical properties of violanthrone (V1) and two 16,17-R derivatives with R = OC(8)H(17) and OCOC(17)H(35) (V2 and V3, respectively) in solution were examined. The fluorescence quantum yield of V3 is Phi(f) = 0.2, while that of V1 is low (0.

Reduction of the polynuclear quinonoid dyes 16,17-dihydroxy- and dimethoxyviolanthrone with photogenerated radicals.

The radical-induced reduction of 16,17-dihydroxy- (M1O2) and 16,17-dimethoxyviolanthrone (M2O2) in argon-saturated 1-phenylethanol or mixtures of dimethyl sulfoxide and acetonitrile or glycerol triacetate was studied by photochemical methods. The photoproduct of MiO2 (i=1, 2) in the presence of a sensitizer, such as acetone, acetophenone or benzophenone, and a donor, e.g.

Photoreduction of 2-methyl-1-nitro-9,10-anthraquinone in the presence of 1-phenylethanol.

The photoreactions of 1-nitro-9,10-anthraquinone (N1) and 2-methyl-1-nitro-9,10-anthraquinone (N2) were studied in benzene and acetonitrile in the presence of 1-phenylethanol. For N2, a short-lived 10 ns transient observed upon flash photolysis is attributed to a triplet state, which can be intercepted by 1-phenylethanol to form a monohydro radical of N2 and a spectroscopically not detectable donor-derived radical. The decay of radicals yields the corresponding nitroso compound and eventually 1-amino-2-methyl-9,10-anthraquinone (A2) as photoproduct.