Concentration and molecular weight dependence of the quenching of Ru(bpy)(3)(2+) by ferricyanide in aqueous solutions of synthetic hyaluronan

Citation
T. Kluge et al., Concentration and molecular weight dependence of the quenching of Ru(bpy)(3)(2+) by ferricyanide in aqueous solutions of synthetic hyaluronan, MACROMOLEC, 33(2), 2000, pp. 375-381
Citations number
25
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Organic Chemistry/Polymer Science
Journal title
MACROMOLECULES
ISSN journal
0024-9297 → ACNP
Volume
33
Issue
2
Year of publication
2000
Pages
375 - 381
Database
ISI
SICI code
0024-9297(20000125)33:2<375:CAMWDO>2.0.ZU;2-B
Abstract
The quenching of electronically excited RU(bpy)(3)(2+) (bpy = 2,2'-bipyridi ne) by ferricyanide (FC) in highly viscous aqueous solutions of synthetic h yaluronan (HA) was studied. The quenching reaction was found to occur by di rect electron transfer at short times and by diffusional encounter at longe r times after the excitation flash. Intrinsic and diffusional quenching rat e constants were found to decrease with increasing polymer concentration bu t not with increasing molecular weight of HA although the effect of both pa rameters on macroscopic viscosity was comparable. It was also found, that t he lifetime of the sensitizer increased with increasing polymer concentrati on, indicating retarded quenching by oxygen. Efficient diffusion of the rea ctants in the aqueous pseudophase occurs even in solutions with high macros copic viscosity. We compared two kinds of HAs (biosynthetic and animal sour ce) in the present experiments and obtained a sharp contrast in photochemic al properties between them while other observable macroscopic parameters sh owed no difference. Biosynthetic HA is more suitable for the systematic; st udy to elucidate the molecular weight dependence of the present photochemic al properties showing microscopic aspects of the HA solution.