Bromide Photo-oxidation Sensitized to Visible Light in Consecutive Ion Pairs.
The titration of bromide into a [Ru(deeb)- (bpz)] (Ru, deeb = 4,4'-diethylester-2,2'-bipyridine; bpz = 2,2'-bipyrazine) dichloromethane solution led to the formation of two consecutive ion-paired species, [Ru, Br-] and [Ru, 2Br-], each with distinct photophysical and electron-transfer properties. Fo...
| Publicado en: | Journal of the American Chemical Society Vol. 139; no. 42; pp. 14983 - 14992 |
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| Autores principales: | , , |
| Formato: | Artículo |
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American Chemical Society
10/25/2017
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| Acceso en línea: | Ver este registro en EBSCOhost |
| fields | @attributes: recordID: 1 pdfLink: plink: https://search.ebscohost.com/login.aspx?direct=true&db=hlh&AN=125898993&site=ehost-live header: @attributes: shortDbName: hlh uiTerm: 125898993 longDbName: Humanities International Complete uiTag: AN controlInfo: bkinfo: jinfo: jid: 00027863 ACS jtl: Journal of the American Chemical Society issn: 00027863 maglogo: N pubinfo: dt: 10/25/2017 vid: 139 iid: 42 pid: 997 pub: American Chemical Society artinfo: ui: 125898993 10.1021/jacs.7b06735 ppf: 14983 ppct: 9 formats: tig: atl: Bromide Photo-oxidation Sensitized to Visible Light in Consecutive Ion Pairs. aug: au: Guocan Li Swords, Wesley B. Meyer, Gerald J. affil: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States su: Bromides Volumetric analysis Density functional theory Photoluminescence Ion pairs Charge exchange sug: subj: Bromides Volumetric analysis Density functional theory Photoluminescence Ion pairs Charge exchange ab: The titration of bromide into a [Ru(deeb)- (bpz)] (Ru, deeb = 4,4'-diethylester-2,2'-bipyridine; bpz = 2,2'-bipyrazine) dichloromethane solution led to the formation of two consecutive ion-paired species, [Ru, Br-] and [Ru, 2Br-], each with distinct photophysical and electron-transfer properties. Formation of the first ion pair was stoichiometric, K>106 M-1 and the second ion-pair equilibrium was estimated to be K = (2.4 ± 0.4) x 10 M. The 1H NMR spectra recorded in deuterated dichloromethane indicated the presence of contact ion pairs and provided insights into their structures and were complimented by density functional theory calculations. Static quenching of the [Ru(deeb)- (bpz)]a* photoluminescence intensity (PLI) by bromide was observed and [Ru, Br-]* was found to be nonluminescent, τ < 10 ns. Further addition of bromide resulted in partial recovery of the PLI and [Ru, 2Br-]* was found to be luminescent with an excited-state lifetime of τ = 65 ± 5 ns. Electrontransfer products were identified as the reduced complex, [Ru(deeb)(bpz)2] and dibromide, Br2 •-. The bromine atom, Br•, was determined to be the primary excited-state electron-transfer product and was an intermediate in Br •- formation, Br• + Br → Br2 •-, with a second-order rate constant, k = (5.4 ± 1) × 10 M s. The unusual enhancement in PLI for [Ru, 2Br-]* relative to [Ru, Br-]* was due to a less favorable Gibbs free energy change for electron transfer that resulted in a smaller rate constant, ket = (1.5-0.2) × 107 s, in the second ion pair. Natural atomic charge analysis provided estimates of the Coulombic work terms associated with ion pairing, ΔGw, that were directly correlated with the measured change in rate constants. pubtype: Academic Journal doctype: Article src: R language: English refInfo: copyright: @attributes: flag: Y dt: @attributes: year: 2017 holdings: @attributes: islocal: N |
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