Photoisomerization and time-resolved Raman studies of 15-15'-cis-.beta.-carotene and 15-15'-trans-.beta.-carotene

Carotenoids and polyterpenoids

“…The 6-lactones [( 278) and ( 279)] of ( I 32)-12-(hydroxymethyl)-retinoic acid (28 1 ) and ( I 32)-12-carboxyretinol (282) [and the &lactones of their (1 1 E, 13Z)-isomers] have been prepared from the half-esters ( 132)-12-carbomethoxyretinoic acid (283) and methyl ( I 32)-12-carboxyretinoate (284), which were obtained by methanolic saponification of ( I 323-1 2-carboxyretinoic anhydride (280) or by partial methylation of (1 1E,1 32)-12-~arboxyretinoic acid (285).' 36 Reduction of the (1 3Z)-6-lactones ( 278) and ( 279) gave (1 32)-12-(hydroxymethyl)retinol (286), which could not be made by reduction of (1 32)-12-carboxyretinoic acid dimethyl ester (287) with LiA1H4, only the (1 lZ,l3E)-and (1 lE,13Z)-isomers being obtained.I3' Many exotic retinoid structures have been synthesized, mostly containing aromatic (benzene, naphthalene, or heterocyclic) rings. These include a series of conformationally restricted benzenoid derivatives ( 288)-( 292),' 38 some containing a 7,8dihydro-or 7,8-methano-group.…”

Picosecond time-resolved resonance Raman scattering and absorbance changes from carotenoids in light-harvesting systems of photosynthetic bacterium Chromatium vinosum

“…In in vivo preparations, the intensity of the T, -T" transition is approximately 2-3 times more intense than the singlet l'A, -1*BU transition. [4][5][6][7][8][9][10][11][12][13][14][15][16][17] Previously, absorption from the excited singlet states (either 11 B" or 2'Ag) has been reported for carotenoids in chromatophores from Rhodospirillum rubrum.11 Given the laser powers and the time resolution in these experiments, 35 ps, it was not possible to assign the transition to a specific excited singlet state (l'Bu or 2'Ag) or to clearly separate the absorbance contributions of the excited-triplet state.17 Consequently, the rates of decay of the 2IA. state to form either ground-state or triplet-state carotenoid coufd not be determined.…”

Light scattering spectroscopy of pure fluids

“…The HH case is more complicated, but the symmetry is longitudinal. If we arbitrarily let the incident light propagate along the x axis, and define the scattering plane as the xy plane, then the spectra will be determined by the following components of the dielectric tensor in the laboratory frame S\\(q,a)) oc <Aezz(q,cv) Aezz*(q,0)) (6) Sm(q,u) = (Ae>z(q,o) Atyz(q,0)> Shh(5.«) , ) sin 9 -Atyy(q,o>) cos 9] X [Aeyx*(q,0) sin 9 -Aeyy*(q,0) cos 9]) One of the most important properties of liquids is that they are isotropic. This means that the quantities which describe the liquid are independent of the direction in which they are measured.…”