Optical and photoinduced electron transfer in ion pairs of coordination compounds

Billing, Roland

doi:10.1016/s0010-8545(96)01288-x

Cited by 25 publications

(14 citation statements)

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“…DOM may act as an electron donor (Fig. 2a, 2b) in environmental media by forming a charge transfer complex with Hg or by generating radicals in the presence of solar radiation (Billing 1997;Ravichandran 2004), thereby initiating photochemical reduction of Hg(II) to Hg(0) (Allard and Arsenie 1991;Xiao et al 1995;Costa and Liss 1999;Tseng et al 2004;Zhang 2006;Bartels-Rausch et al 2011). Alternatively, DOM may act to bind and sequester Hg(II) (Fig.…”

Section: Dissolved Organic Mattermentioning

confidence: 99%

Mercury photochemistry in snow and implications for Arctic ecosystems

2014

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Mercury is a toxic and bioaccumulative environmental contaminant, which may be transported to remote regions around the world, such as the Arctic. Snowmelt is a major source of mercury to many surface water environments, but the amount of mercury in snow varies considerably. This variation is due to the balance of mercury retention and losses from snow, which is largely controlled by photochemical mechanisms controlling speciation. As such, quantifying these photochemical reaction rates and the factors affecting them will allow for the prediction of mercury speciation and movement into receiving water bodies. This will consequently improve our ability to predict exposure of aquatic organisms to mercury. This review highlights knowledge gaps in the quantification of mercury photochemical kinetics and the specific research required to advance the science of mercury photochemistry in snow, while examining the physical and chemical snowpack variables that influence snowpack mercury reactions. At present, our lack of mechanistic and kinetic knowledge of mercury reactions in snow is one of the greatest gaps preventing accurate predictions of mercury fate in regions containing seasonal snowpacks.Résumé : Le mercure constitue un contaminant environnemental toxique et biocumulatif, pouvant être transporté dans des régions éloignées partout au monde, comme dans l'Arctique. La fonte des neiges représente une source majeure de mercure pour plusieurs plans d'eau de surface, mais la quantité de mercure dans la neige varie considérablement. Cette variation est due à la balance entre la rétention du mercure et les pertes à partir de la neige, celles-ci étant fortement contrôlées par des mécanismes photochimiques déterminant la spéciation. Comme telle, la quantification des taux de ces réactions photochimiques et des facteurs les affectant permettront de prédire la spéciation du mercure et le mouvement vers les milieux aquatiques réceptifs. Conséquemment, ceci améliorera notre capacité à prédire l'exposition des organismes aquatiques au mercure. Cette revue insiste sur les manques de connaissances concernant la quantification de la cinétique photochimique du mercure ainsi que les recherches spécifiques nécessaires à l'avancement de la science sur la photochimie du mercure dans la neige, tout en examinant les variables physiques et chimiques influençant les réactions du mercure dans les bancs de neige. Présentement, l'absence de connaissances mécanistiques et cinétiques des réactions du mercure dans la neige constitue une des plus grandes lacunes empêchant les prédictions sur le devenir du mercure dans les régions connaissant des enneigements saisonniers. [Traduit par la Rédaction]

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Section: Dissolved Organic Mattermentioning

confidence: 99%

Mercury photochemistry in snow and implications for Arctic ecosystems

2014

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“…The absorption spectra of the halides in water is dominated by two absorption bands in the UV region. These have been assigned as charge-transfer-to-water transitions that are sometimes referred to simply as outer-sphere charge-transfer transitions. , The appearance of two transitions is understood by the doublet X • products, 2 P 1/2 and 2 P 3/2 . − In keeping with periodic trends, one would anticipate that iodide would absorb light at the longest wavelength (lowest energy) and chloride at the shortest value, a trend that is approximately followed given the spread of literature values, Table . Direct confirmation of the charge-transfer assignment comes from studies where the solvated electron was directly observed after pulsed laser excitation into these charge-transfer absorption bands.…”

Section: Introductionmentioning

confidence: 99%

Halide Photoredox Chemistry

et al. 2019

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Halide photoredox chemistry is of both practical and fundamental interest. Practical applications have largely focused on solar energy conversion with hydrogen gas, through HX splitting, and electrical power generation, in regenerative photoelectrochemical and photovoltaic cells. On a more fundamental level, halide photoredox chemistry provides a unique means to generate and characterize one electron transfer chemistry that is intimately coupled with X−X bond-breaking and -forming reactivity. This review aims to deliver a background on the solution chemistry of I, Br, and Cl that enables readers to understand and utilize the most recent advances in halide photoredox chemistry research. These include reactions initiated through outer-sphere, halide-to-metal, and metal-toligand charge-transfer excited states. Kosower's salt, 1-methylpyridinium iodide, provides an early outer-sphere charge-transfer excited state that reports on solvent polarity. A plethora of new inner-sphere complexes based on transition and main group metal halide complexes that show promise for HX splitting are described. Long-lived charge-transfer excited states that undergo redox reactions with one or more halogen species are detailed. The review concludes with some key goals for future research that promise to direct the field of halide photoredox chemistry to even greater heights. CONTENTS 1. Introduction, Background, and Motivation

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“…These compounds were also found to behave as molecular magnets [29] with potential applications as molecular devices or memory devices. Some of them also revealed very specific optical properties including ion pair charge-transfer (IPCT) [30] transitions corresponding to the transfer of electrons from the complex anions to the complex cations in the visible and near-ultraviolet spectral regions. This phenomenon was confirmed for ionic pair compounds involving both [Co( en ) 3 ] 3+ and [M(CN) x ] 4– (for x = 6, M = Fe, Ru, Os; for x = 8, M = Mo, W) complex ions [31].…”

Section: Introductionmentioning

confidence: 99%

Thermal decomposition of [Co(en)3][Fe(CN)6]∙ 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation

Trávníček

Zbořil

Matiková-Maľarová

et al. 2013

Chemistry Central Journal

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BackgroundThe Prussian blue analogues represent well-known and extensively studied group of coordination species which has many remarkable applications due to their ion-exchange, electron transfer or magnetic properties. Among them, Co-Fe Prussian blue analogues have been extensively studied due to the photoinduced magnetization. Surprisingly, their suitability as precursors for solid-state synthesis of magnetic nanoparticles is almost unexplored.In this paper, the mechanism of thermal decomposition of [Co(en)3][Fe(CN)6] ∙∙ 2H2O (1a) is elucidated, including the topotactic dehydration, valence and spins exchange mechanisms suggestion and the formation of a mixture of CoFe2O4-Co3O4 (3:1) as final products of thermal degradation.ResultsThe course of thermal decomposition of 1a in air atmosphere up to 600°C was monitored by TG/DSC techniques, 57Fe Mössbauer and IR spectroscopy. As first, the topotactic dehydration of 1a to the hemihydrate [Co(en)3][Fe(CN)6] ∙∙ 1/2H2O (1b) occurred with preserving the single-crystal character as was confirmed by the X-ray diffraction analysis. The consequent thermal decomposition proceeded in further four stages including intermediates varying in valence and spin states of both transition metal ions in their structures, i.e. [FeII(en)2(μ-NC)CoIII(CN)4], FeIII(NH2CH2CH3)2(μ-NC)2CoII(CN)3] and FeIII[CoII(CN)5], which were suggested mainly from 57Fe Mössbauer, IR spectral and elemental analyses data. Thermal decomposition was completed at 400°C when superparamagnetic phases of CoFe2O4 and Co3O4 in the molar ratio of 3:1 were formed. During further temperature increase (450 and 600°C), the ongoing crystallization process gave a new ferromagnetic phase attributed to the CoFe2O4-Co3O4 nanocomposite particles. Their formation was confirmed by XRD and TEM analyses. In-field (5 K / 5 T) Mössbauer spectrum revealed canting of Fe(III) spin in almost fully inverse spinel structure of CoFe2O4.ConclusionsIt has been found that the thermal decomposition of [Co(en)3][Fe(CN)6] ∙∙ 2H2O in air atmosphere is a gradual multiple process accompanied by the formation of intermediates with different composition, stereochemistry, oxidation as well as spin states of both the central transition metals. The decomposition is finished above 400°C and the ongoing heating to 600°C results in the formation of CoFe2O4-Co3O4 nanocomposite particles as the final decomposition product.

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Optical and photoinduced electron transfer in ion pairs of coordination compounds

Cited by 25 publications

References 50 publications

Mercury photochemistry in snow and implications for Arctic ecosystems

Mercury photochemistry in snow and implications for Arctic ecosystems

Halide Photoredox Chemistry

Thermal decomposition of [Co(en)3][Fe(CN)6]∙ 2H2O: Topotactic dehydration process, valence and spin exchange mechanism elucidation

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