Intrazeolitic photochemical charge separation for Ru(bpy){sub 3}{sup 2+}-bipyridinium system: Role of the zeolite structure
- Ohio State Univ., Columbus, OH (United States). Dept. of Chemistry
The pore structure of zeolite Y consists of 13 {angstrom} supercages connected through 7 {angstrom} windows. This study deals with the intrazeolitic photoelectron transfer from trisbipyridyl ruthenium(II) (Ru(bpy){sub 3}{sup 2+}) synthesized within zeolite Y supercages to ion-exchanged bipyridinium molecules in neighboring supercages. Three N,N{prime}-dialkyl-2,2{prime}-bipyridinium ions and a 4,4{prime}-bipyridinium ion with reduction potentials varying from {minus} 0.37 to {minus}0.65 V have been studied. For the 2,2{prime}-bipyridinium salts (members of the diquat family), two, three, and four CH{sub 2} bridging units abbreviated as 2DQ{sup 2+}, 3DQ{sup 2+}, and 4DQ{sup 2+}, respectively, have been examined. The fourth viologen is 1,1{prime}-dimethyl-4,4{prime}-bipyridinium, commonly known as methyl viologen and abbreviated here as MV{sup 2+}. Because of the limitations of the time-resolved diffuse reflectance instrument, only a lower limit of the forward electron transfer rate constant from Ru(bpy){sub 3}{sup 2+}* to the bipyridinium ion was obtained and is > 10{sup 7} s{sup {minus}1}. The back electron transfer from the photogenerated bipyridinium radical ions to Ru(bpy){sub 3}{sup 3+} was monitored at different intrazeolitic bipyridinium concentrations. A model that allows for electron exchange processes between bipyridinium ions to compete with the back electron transfer was necessary. This kinetic model allowed them to extract the back electron transfer rate at high loadings along with the rate constants for electron hopping 2DQ{sup 2+}, MV{sup 2+}, 3DQ{sup 2+}, and 4DQ{sup 2+} with high loading, the back electron transfer rate constants were 2.5 {times} 10{sup 5}, 9 {times} 10{sup 4}, 1.8 {times} 10{sup 5}, and 1.2 {times} 10{sup 5} s{sup {minus}1}, higher than the low loading samples. In the high loading case, longer lived charge separation was observed because of the presence of a route for charge propagation by electron hopping via the densely packed viologen molecules.
- OSTI ID:
- 345114
- Journal Information:
- Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical, Journal Name: Journal of Physical Chemistry B: Materials, Surfaces, Interfaces, amp Biophysical Journal Issue: 13 Vol. 103; ISSN JPCBFK; ISSN 1089-5647
- Country of Publication:
- United States
- Language:
- English
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