Kinetik und Mechanismus der elektrochemischen Reduktion von 2,2′-DipyridylI. Primärprozesse: Vorgelagerte Isomerisierung eines Komplexes

Erhard, H.; Jaenicke, Walther

doi:10.1016/s0022-0728(75)80158-6

Cited by 9 publications

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“…The reduction of the 2,2‘-bipy has been previously investigated . In our experiments, bleaching of the ligand absorptions associated with π to π* electronic transitions suggests hydrogenation of the azine.…”

Section: Referencesmentioning

confidence: 52%

“…By contrast to the (2,2‘-biq) complexes, little if any Re(CO) 3 (2,2‘-bipy) • )O 2 C-pz - was produced by reactions of Re(CO) 3 (2,2‘-bipy)O 2 C-pz with radicals from the oxidation of TEOA. However, the spectral changes on a 200 μs time scale corresponded to the formation of a Re(I) complex with a hydrogenated 2,2‘-bipy ligand, e.g., 2,2‘-bipyH 2 , Figure . ,, The process is too fast to be the disproportionation of Re(I) ligand-radicals, i.e., one observed on a 10 2 ms time scale with Re(CO) 3 ((2,2‘-biq) • )L S species. These experimental observations suggest that TEOA radicals reduced a fraction of the Re(CO) 3 ((2,2‘-bipy) • )O 2 C-pz - that were formed during the quenching of the excited state.…”

Section: Resultsmentioning

confidence: 98%

“…The values for the ratio of the rate constant to the extinction coefficient, k /ε = 6.5 × 10 3 cm s -1 for L S = 4,4‘-bipy and k /ε = 2.4 × 10 4 cm s -1 for L S = pz, were calculated by such least-squares fitting of data collected at λ ob 480 nm. The second-order reactions of Re(CO) 3 ((2,2‘-biq) • )L S can be attributed to their disproportionation into the parent complex and Re(CO) 3 ((2,2‘-biq)H 2 )L S , i.e., a species where a double bond of the (2,2‘-biq) ligand has been hydrogenated. ,, …”

Section: Resultsmentioning

confidence: 99%

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Photochemical and Photophysical Reactions of fac-Rhenium(I) Tricarbonyl Complexes. Effects from Binucleating Spectator Ligands on Excited and Ground State Processes

et al. 2001

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Ground and excited state properties of the newly prepared complexes Re(CO) 3 (2,2′-biquinoline)L S + , L S ) pyrazine or 4,4′-bipyridine, and Re(CO) 3 (2,2′-bipy)(2-pyrazinecarboxylate) were investigated by steady state and time-resolved spectroscopy. The X-ray structure of the latter compound showed that the spectator ligand 2-pyrazinecarboxylate is coordinated through the carboxylate group to Re(I). A component of the complexes' luminescence was associated with long-lived Re to ligand, 2,2′-biquinoline or 2,2′-bipy, charge transfer, while a fast component of the emission was associated with intraligand excited states. Quenching of the luminescence by CuCl 2 involved energy transfer via dynamic and static mechanisms. The complexes in their excited states were reduced by 2,2′,2′′-nitrilotriethanol with the formation of Re(I) ligand-radical species. Similar products were generated by the pulse radiolytic reduction of the complexes. The photochemical properties of the 2,2′-biquinoline complexes and Re(CO) 3 (1,10-phen)4-nitrobenzoate are compared, and the mechanisms of their photochemical reactions are discussed.

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Section: Referencesmentioning

confidence: 52%

Section: Resultsmentioning

confidence: 98%

Section: Resultsmentioning

confidence: 99%

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Photochemical and Photophysical Reactions of fac-Rhenium(I) Tricarbonyl Complexes. Effects from Binucleating Spectator Ligands on Excited and Ground State Processes

et al. 2001

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“…For the electrochemically generated IV,IV'-dihydrobipyridine, a OH'-catalyzed isomerization (k = 220 M'1 s'1) followed by further slower rearrangements to the 2,5-dihydrobipyridine isomer has been reported. 38 The first-order process we observe may be solvent-catalyzed isomerization or the formation of a covalent hydrate species. 39 We cannot say whether this reaction is followed by other slower reactions.…”

Section: Discussionmentioning

confidence: 86%

One-electron reduction of aromatic nitrogen heterocycles in aqueous solution. 2,2'-Bipyridine and 1,10-phenanthroline

Mulazzani¹,

Emmi²,

Fuochi³

et al. 1979

J. Phys. Chem.

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Publication costs assisted by the National Science FoundationThe reaction of 2,2'-bipyridine (bpy), 1,lO-phenanthroline (phen), and their monoprotonated cations (bpyH+ and phenH+) with radiation-generated one-electron reducing agents yields radicals, the spectra, kinetics, and acid-base properties of which have been established. BpyH2+. has a pK, of 5.6 and exhibits an intense absorption maximum at 375 nm ( e 4.5 X lo4 M-l cm-' 1; bpyH. shows A, , , 365 nm ( E 3.0 X lo4 M-' cm-'). BpyH. decays via second-order kinetics (2h = 4.0 X lo9 M-' sd) representing primarily a disproportionation reaction. BpyH2+. appears to decay via concurrent first-and second-order reactions; the processes are complicated by unidentified dose-dependent sequences. Irrespective of pH, the final isolatable product is a pale yellow solid which can be identified by elemental analysis, molecular weight determination, and IR spectrum as a trimer of dihydrobipyridine isomers. PhenHz+. shows A,, 370 nm (e 7.8 X lo3 M-' cm-l ) and 510 nm ( e 3.8 X lo3 M-l cm-' ) and pK, = 6.3 while phenH. exhibits A, , , 350 nm ( E 5.8 X lo3 M-' cm-' ) and 475 nm (t 3.0 X lo3 M-' cm-l ).PhenH. protonates to form phenHz+-with k = 8.3 X lo9 M-' s-' a nd phenHz+. decays via second-order kinetics (2k = 1.6 x lo9 M-l s-l ). In alkaline solution (pH 10-13) the decay of phenH. is first order ( k = 2 X IO3 9-l).The bimolecular reaction appears to proceed predominantly via combination; a product has been isolated with the empirical formula C12HllN2C104. The behavior of the one-electron reduction products is compared with that of species believed to be similar arising from the photoreduction of bpy and phen in aqueous solution.

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Cathodic reductions of 2,2′-bipyridine and 4,4′-bipyridine in liquid ammonia

Brown

Butterfield

1982

Electrochimica Acta

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Kinetik und Mechanismus der elektrochemischen Reduktion von 2,2′-DipyridylI. Primärprozesse: Vorgelagerte Isomerisierung eines Komplexes

Cited by 9 publications

References 0 publications

Photochemical and Photophysical Reactions of fac-Rhenium(I) Tricarbonyl Complexes. Effects from Binucleating Spectator Ligands on Excited and Ground State Processes

Photochemical and Photophysical Reactions of fac-Rhenium(I) Tricarbonyl Complexes. Effects from Binucleating Spectator Ligands on Excited and Ground State Processes

One-electron reduction of aromatic nitrogen heterocycles in aqueous solution. 2,2'-Bipyridine and 1,10-phenanthroline

Cathodic reductions of 2,2′-bipyridine and 4,4′-bipyridine in liquid ammonia

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