Photoisomerisation kinetics

Actually, the apparent rate constant of the photoisomerisation in a viscous media, like biological membranes, was found to be dependent upon the medium relaxation rate. Hence, it is possible to study the dynamics of proteins and biological membranes in the vicinity of the incorporated stilbene probe by monitoring the steady-state fluorescence decay of the stilbene probe with the conventional constant-illumination spectrofluorimeter. The experimental values of a (j>n Icx can be measured independently or can be omitted by comparison with photoisomerisation kinetics of the same probe and similar conditions in a medium with known macro- and microviscosity. A combined analysis of the trans-cis photoisomerisation kinetics of a stilbene probe and its polarization allows the establishment of the mechanism and the estimation of the... 

The triplet-photochrome labeling method has been used to study very rare encounters in a system containing the Erythrosin B sensitiser and SITC photochrome probe (Mekler and Likhtenshtein, 1986). Both types of the molecules were covalently bound to a-chymotrypsin. The photoisomerisation kinetics was monitored by fluorescence decay of the frans-SITS. The rate constants of the triplet-triplet energy transfer between Erythrosin B and SITS (at room temperature and pH 7) were found k,r = 2 xlO7 NT s-1 and ktT = 107 M V. It should be emphasized that the concentration of the triplet sensitiser attached to the protein did not exceed 10 7 M in those experiments, and the collision frequencies were close to 10 s 1 which are 8-9 orders of magnitude less than those measured with the regular luminescence or ESR techniques. 

The photoisomerisation kinetics and other properties of the 1 1 inclusion complexes formed between aromatic derivatives of norbomadiene and P-cyclo-dextrin have been measured." (S)- or (R)-2-Chloropropiophenone affords partially racemised (S)- or (R)-2-phenylpropionic acid respectively by a photo-induced rearrangement via what is probably an ion or radieal intermediate," and (Z)-N-substituted benzoyl-a-dehydrophenylalanines such as (7) are photo-isomerised to 1-azetidine derivatives (8) by a 1,3-acyl migration. Irradiation of 9,9 -bifluorene-9,9 -diol (9) gives a mixture of fluoren-9-one and spiro[9H-fluorene-9,9 (10 -H)-phenanthren]-10 -one (10) whose composition is solvent dependent with the more polar solvents favouring (10). Laser flash photolysis shows the presence of two transients, one of which can be identified with the 9-fluorenyl cation (11), and which originates from photoheterolysis of the diol (9). There is also evidence to support the view that unimolecular rearrange-... 

Schroeder J 1997 Picosecond kinetics of trans-cis photoisomerisations from ]et-cooled molecules to compressed solutions Ber. Bunsenges Phys. Chem. 101 643... 

A DFT-based computational study has established the thermal and photochemical isomerisation mechanisms from the terminal P-bound phosphinidene oxide complex [Ru(tpy)(bpy)(POPh)] to the corresponding O-bound, [Ru(tpy)(bpy)(OPPh)] . Thermal isomerisation was found to be both kinetically and thermodynamically unfavourable, while photoisomerisation can readily take place by either adiabatic or non-adiabatic pathways. The different absorption spectra of the two isomers and the bi-stability of the system make this complex a good candidate for photochromism. ... 

The resulting films were characterized by FllK and UV-VIS spectroscopies before and after imidization. It was studied kinetics imidization at different temperatures. The results show that optimal conditions for imidization are temperature 300 °C for 1 h. It is known that azobenzene derivatives possess optical properties associated with optical anisotropy due to photoisomerisation photoorientation of azochromophore, perpendicular to the direction of the polarized beam. These properties of azobenzene derivatives are important for their application in nonlinear optics and nanotechnology, optical modulators, optical recording media and other devices [16,17,18,19]. 

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