Excited-state Electron-transfer Reactions Research Articles

Nonequilibrium and nonadiabatic effects on excited state electron transfer reactions in solution

Picosecond emission spectroscopy is used to examine the intramolecular charge transfer reaction of N,N-dimethylaminophenyl sulphone in alcohol solution. The effects of nonequilibrium distributions on the reaction surface as well as nonadiabatic effects arising from the time scale of the reactive process and solvent diffusion are discussed. The implications of these data on the motion along the reaction potential energy surface are described.

Singlet quenching of chlorophyll a by nitroaromatics. Effect of solvents on the electron transfer from excited singlet of chlorophyll a to nitroaromatic acceptors

Optical absorption and singlet emission properties of chlorophyll a in the presence of diverse nitroaromatic acceptors of varying ring size and electron affinity have been investigated. Chl a forms 1:1 intermolecular complexes with the acceptors and the nature of interaction between the donor Chl a and the acceptor has its origin in charge transfer. The K sv values are found to vary linearly with the electrochemical reduction potentials of the acceptors. The oxidation potential of the excited singlet state of Chl a, Chl a ∗ Chl a + is found to be 1.28 V vs. saturated calomel electrode. The rates of bimolecular quenching ( k q) increase linearly with the change in free-energy for the excited-state electron transfer reaction in the weakly exergonic region, indicating that the electron transfer reaction is predominantly controlled by the activation energy. In the moderate exergonic region, the k q values increase exponentially, with ΔG 23 values without the exhibition of inverted region even upto a ΔG 23 value of − 100 kJ · mol −1. This has been ascribed to the presence of low-lying electronically excited state in the ion-pair. The ΔG 23 values have been used to distinguish the various acceptors based on their ability to form ionic or covalent exciplexes with Chl a. Ten solvents of varying polarizability and viscosity have been employed to study the influence of the rates of excited state electron transfer in Chl a-tetranitrofluorenone system. The solvent reorganization energies are found to over-estimate the magnitudes of free-energy change for radical-pair formation, ΔG rip. It is shown that specific solvent effects, viz. H-bonding and coordinating ability, contribute to the k q values. It is found that solvents can interact specifically with Chl a exhibiting maximum efficiency of quenching of the singlet emission of Chl a by the acceptor.

Solution Medium Control of the Ru(bpy) 32+/Methyl Viologen/EDTA Photochemical System

The value of φ(MV +·) from the photolysis of the Ru(bpy) 3 2+/MV 2+/EDTA system depends on the pH of the solution and the concentrations of the three components. The pairing of cations with EDTA in alkaline solution, and the formation of large aggregates at high substrate concentrations, affects the yields of redox products from the excited-state electron-transfer reaction. The degree of linearity of Stern-Volmer luminescence quenching plots, and the values of the quenching rate constants, are functions of solution medium.

Preparation and characterisation of 2,2′-bipyridine-4,4′-disulphonic and -5-sulphonic acids and their ruthenium(II) complexes. Excited-state properties and excited-state electron-transfer reactions of ruthenium(II) complexes containing 2,2′-bipyridine-4,4′-disulphonic acid or 2,2′-bipyridine-4,4′ dicarboxylic acid

We report the syntheses of 2,2′-bipyridine-4,4′-disulphonic acid (H2bp-4,4′-ds) and 2,2′-bipyridine-5-sulphonic acid (Hbp-5-s), and several ruthenium(II) complexes derived therefrom, including [Ru(bp-4,4′-ds)3]4–,[Ru(bipy)(bp-4,4′-ds)2]2–(bipy = 2,2′-bipyridine), [Ru(bipy)2(bp-4,4′-ds)], and [Ru(bp-5-s)3]– and their 2,2′-bipyridine-4,4′-dicarboxylic acid (H2bpdc) analogues, viz. [Ru(bpdc)3]4–, [Ru(bipy)(bpdc)2]2–, and [Ru(bipy)2(bpdc)]. Some novel thioalkyl derivatives of 2,2′- bipyridine, including 4,4′-di(methylthio)-2,2′-bipyridine, 4,4′-di(ethylthio)-2,2′-bipyridine, and 4,4′,6,6′-tetra(methylthio)-2,2′-bipyridine, were also prepared and characterised during the course of this investigation. The luminescent states of the complexes [Ru(bp-4,4′-ds)3]4–,[Ru(bipy)(bp-4,4′ds)2]2–, [Ru(bpdc)3]4–, [Ru(bipy)(bpdc)2]2–, and [Ru(bipy)2(bpdc)] were studied using variabletemperature lifetime measurements. Studies of the quenching of {[Ru(bipy)3]2+}*, {[Ru(bipy)2(bpdc)]}*, {[Ru(bipy)(bp-4,4′-ds)2]2–}*, and {[Ru(bp-4,4′-ds)3]4–}* by 1,1′-dimethyl-4,4′-bipyridinium bromide (methyl viologen) in aqueous solution as a function of ionic strength have demonstrated that the effects of charge in these electron-transfer reactions can be understood in terms of conventional theories of ionic reactions whilst, at the same time, confirming the effective charges of the ruthenium(II) complex ions. The rate constants for the quenching of {[Ru(bp-4,4′-ds)3]4–}* and {[Ru(bipy)(bp-4,4′-ds)2]2–}* by copper(II) ions in neutral aqueous solution show unusual (non-Arrhenius) temperature dependences. A novel kinetic scheme involving parallel innerand outer-sphere quenching mechanisms has been proposed to account for the observed behaviour. The luminiscence decay of {[Ru(bipy)2(bpdc)]}* in the presence of aqueous copper(II) ions at pH 3.5 is non-exponential. This is interpreted in terms of a combination of static and dynamic quenching effects.

ChemInform Abstract: GROUND‐ AND EXCITED‐STATE ELECTRON‐TRANSFER REACTIONS: PHOTOINDUCED REDOX REACTIONS OF POLY(PYRIDINE)RUTHENIUM(II) COMPLEXES AND COBALT(III) CAGE COMPOUNDS

Chemischer InformationsdienstVolume 15, Issue 50 Organoelement Compounds ChemInform Abstract: GROUND- AND EXCITED-STATE ELECTRON-TRANSFER REACTIONS: PHOTOINDUCED REDOX REACTIONS OF POLY(PYRIDINE)RUTHENIUM(II) COMPLEXES AND COBALT(III) CAGE COMPOUNDS C.-Y. MOK, C.-Y. MOKSearch for more papers by this authorA. W. ZANELLA, A. W. ZANELLASearch for more papers by this authorC. CREUTZ, C. CREUTZSearch for more papers by this authorN. SUTIN, N. SUTINSearch for more papers by this author C.-Y. MOK, C.-Y. MOKSearch for more papers by this authorA. W. ZANELLA, A. W. ZANELLASearch for more papers by this authorC. CREUTZ, C. CREUTZSearch for more papers by this authorN. SUTIN, N. SUTINSearch for more papers by this author First published: December 11, 1984 https://doi.org/10.1002/chin.198450330AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume15, Issue50December 11, 1984 RelatedInformation

Ground- and excited-state electron-transfer reactions: photoinduced redox reactions of poly(pyridine)ruthenium(II) complexes and cobalt(III) cage compounds

Donnees cinetiques de la desexcitation de divers complexes Ru(II). Le processus implique un transfert d'energie et un transfert d'electron de * RuL 3 2+ vers Co(cage) 3+ . Bon accord avec un modele adiabatique semiclassique. Rendement

Metal ions in molecular association of porphyrins

Molecular association of porphyrins and their metal derivatives has been recognized as one of the important properties for many of their biological functions. The association is classified into (i) self-aggregation, (ii) intermolecular association and (iii) intramolecular association. The presence of metal ions in the porphyrin cavity is shown to alter the magnitudes of binding constants and thermodynamic parameters of complexation. The interaction between the porphyrin unit and the acceptor is described in terms of π-π interaction. The manifestation of charge transfer states both in the ground and excited states of these complexes is shown to influence the rates of excited state electron transfer reactions. Owing to paucity of crystal structure data, the time-averaged geometries of many of these complexes have been derived from magnetic resonance data.

ChemInform Abstract: REDOX BEHAVIOR OF THE (RH2(1,3‐DIISOCYANOPROPANE)4)26+ ION AT THE ROTATING GLASSY CARBON ELECTRODE

The results of both the oxidation and reduction of the (Rh/sub 2/(bridge)/sub 4/)/sub 2//sup 6 +/ (bridge = 1,3-diisocyanopropane, n = 2,3,4) ion in acedic media at a rotating glassy carbon disk electrode are reported. It is interesting to speculate about the relationship between the extreme irreversibility of the oxidation-reduction reactions and the photochemical production of hydrogen gas from hydrogen ions which have been observed for the Rh/sub 4//sup 6 +/ system. Due to the high-energy requirement for the reduction of hydrogen ions to hydrogen gas via hydrogen atom intermediates and the related back-electron-transfer problem encountered in excited-state electron-transfer reactions, systems such as the (Rh/sub 2/(bridge)/sub 4/)/sub 2//sup 6 +/ system, which are capable of undergoing irreversible two-electron-transfer reactions, will have distinct advantages in the production of hydrogen gas from aqueous solutions. Clearly, systems which display normal behavior (i.e., undergo reversible one-electron transfers) are systems which are unlikely to be able to cause H-H bond formation since they will be unable to supply the second electron to complete the formation of the H/sub 2/ bond before a back-electron-transfer step regenerates hydrogen ions.

Models for Photosynthetic Charge Separation: Excited State Electron Transfer Reactions of Bacteriopheophytin in Micelles

Models for Photosynthetic Charge Separation: Excited State Electron Transfer Reactions of Bacteriopheophytin in Micelles

Temperature dependence of excited-state electron-transfer reactions. Quenching of RuL32+ emission by copper(II) and europium(III) in aqueous solution

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTTemperature dependence of excited-state electron-transfer reactions. Quenching of RuL32+ emission by copper(II) and europium(III) in aqueous solutionJ. E. Baggott and M. J. PillingCite this: J. Phys. Chem. 1980, 84, 23, 3012–3019Publication Date (Print):November 1, 1980Publication History Published online1 May 2002Published inissue 1 November 1980https://doi.org/10.1021/j100460a008RIGHTS & PERMISSIONSArticle Views698Altmetric-Citations18LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts

Differences in the intrinsic barriers between ground- and excited-state electron-transfer reactions from spectroscopic Franck-Condon parameters

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDifferences in the intrinsic barriers between ground- and excited-state electron-transfer reactions from spectroscopic Franck-Condon parametersJohn F. Endicott and Guillermo J. FerraudiCite this: J. Am. Chem. Soc. 1977, 99, 17, 5812–5813Publication Date (Print):August 1, 1977Publication History Published online1 May 2002Published inissue 1 August 1977https://doi.org/10.1021/ja00459a053RIGHTS & PERMISSIONSArticle Views35Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (321 KB) Get e-Alerts Get e-Alerts