Photophysical processes and photoinduced electron transfer reactions of tris(2,2'-bipyridine)ruthenium(II) or ruthenium tri(bipyridine) ion adsorbed onto porous Vycor glass and modified porous Vycor glass.
Item
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Title
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Photophysical processes and photoinduced electron transfer reactions of tris(2,2'-bipyridine)ruthenium(II) or ruthenium tri(bipyridine) ion adsorbed onto porous Vycor glass and modified porous Vycor glass.
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Identifier
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AAI9304658
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identifier
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9304658
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Creator
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Fan, Jianwei.
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Contributor
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Adviser: Harry D. Gafney
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Date
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1992
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Language
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English
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Publisher
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City University of New York.
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Subject
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Chemistry, Physical | Chemistry, Inorganic
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Abstract
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In the 5 to 90{dollar}\sp\circ{dollar}C range, the photophysical and photochemical properties of Ru(bpy){dollar}\sb3\sp{lcub}2+{rcub}{dollar} cation exchanged onto porous Vycor glass, Ru(bpy){dollar}\sb3\sp{lcub}2+{rcub}{dollar}(ads), have been investigated. In contrast to fluid solution behavior, measurements of emission quantum yield, {dollar}\Phi\sb{lcub}\rm em{rcub}{dollar}, and lifetime, {dollar}\tau{dollar}, reveal that the {dollar}\Phi\sb{lcub}\rm em{rcub}{dollar}/{dollar}\tau{dollar} ratio, which is equal to the product of k{dollar}\sb{lcub}\rm r{rcub}\eta\sb{lcub}\rm isc{rcub}{dollar}, declines by 42%. Since spectroscopic data offer no indication that the radiative decay rate constant, k{dollar}\sb{lcub}\rm r{rcub}{dollar}, changes with temperature, the temperature dependence of {dollar}\Phi\sb{lcub}\rm em{rcub}{dollar}/{dollar}\tau{dollar} ratio is attributed to the intersystem crossing yield, {dollar}\eta\sb{lcub}\rm isc{rcub}{dollar}. Fitting the temperature dependent lifetime data for Ru(bpy){dollar}\sb3\sp{lcub}2+{rcub}{dollar}(ads) reveals a decay channel through a level lying 1168 {dollar}\pm{dollar} 160 cm{dollar}\sp{lcub}-1{rcub}{dollar} above the emissive {dollar}\sp3{dollar}MLCT state. Photochemical evidence indicates that it is another MLCT state, rather than a dd state. The temperature dependent emission quantum yield data for Ru(bpy){dollar}\sb3\sp{lcub}2+{rcub}{dollar}(ads) also reveal a higher energy level located 1117 {dollar}\pm{dollar} 70 cm{dollar}\sp{lcub}-1{rcub}{dollar} above the {dollar}\sp1{dollar}MLCT state. Thermal population of this state from the {dollar}\sp1{dollar}MLCT state and subsequent decay to the ground state nonradiatively competes with intersystem crossing to the {dollar}\sp3{dollar}MLCT state. As a result, {dollar}\eta\sb{lcub}\rm isc{rcub}{dollar} decreases as temperature increases. The appearance of these additional decay channels is attributed to the reduction of the symmetry of the complex upon the adsorption. A model of the excited state dynamics of Ru(bpy){dollar}\sb3\sp{lcub}2+{rcub}{dollar}(ads) consistent with both {dollar}\tau{dollar} and {dollar}\Phi\sb{lcub}\rm em{rcub}{dollar} data is presented.;The photoinduced disproportionation of Ru(bpy){dollar}\sb3\sp{lcub}2+{rcub}{dollar}(ads) occurs among a fixed array of immobilized adsorbates by means of a mobile photodetached electron. The role of the surface Lewis acid B{dollar}\sb2{dollar}O{dollar}\sb3{dollar} sites on electron migration has been examined by a selective reaction with NH{dollar}\sb3{dollar}. Measurements of quantum yield as a function of initial loading indicate that the maximum yield in the presence of NH{dollar}\sb3{dollar} occurs at loading of 1.7 {dollar}\times{dollar} 10{dollar}\sp{lcub}-6{rcub}{dollar} moles of Ru(bpy){dollar}\sb3\sp{lcub}2+{rcub}{dollar}/g of PVG, which corresponds to a separation between the adsorbates of 57 A. Since this is equivalent to that in the absence of NH{dollar}\sb3{dollar}, the data indicate that the B{dollar}\sb2{dollar}O{dollar}\sb3{dollar} sites are not involved in the electron migration process. In fact, since the rate of the disproportionation reaction increases in the presence of NH{dollar}\sb3{dollar}, it suggests that the B{dollar}\sb2{dollar}O{dollar}\sb3{dollar} sites actually hinder electron migration on the glass surface.
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Type
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dissertation
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Source
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PQT Legacy CUNY.xlsx
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degree
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Ph.D.
