Mehrstufige reversible Redoxsysteme, XLIII. Voltammetrie von α‐Styrylpyrylium‐Salzen, (1,3‐Cyclobutandiyl)‐und (1,3‐Cyclobutandiyliden)bis(pyrylium)‐Salzen

Hesse, Konrad; Hünig, Siegfried

doi:10.1002/jlac.198519850409

Cited by 8 publications

(8 citation statements)

References 14 publications

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“…In fact, no oxidation peak is observed when the scanning potential (E f ) is reversed before reaching the reduction peak potential (if E f is limited at -0.5 V). This behavior shows that the initial cathodic charge transfer on the pyrylium cation is followed by chemical reaction of the generated radical, as well described in literature [13,15,17,19].…”

Section: Electrochemical Reduction Of Methylstyrylpyrylium Perchloratessupporting

confidence: 82%

“…32 mV per decade (Figure 4). The obtained value is in agreement with a fast electron transfer followed by a first order chemical reaction, confirming that the rate determining step is the dimerization reaction of the pyranyl radical emerging after the fast electron transfer [12,15,19]. Substrate concentration effects.…”

Section: Kinetic Investigation: Elucidation Of the Mechanism Of Reducsupporting

confidence: 75%

“…This means that the pyranyl radical evolves according to a fast chemical reaction which is in conformity with the dimerization reaction. The radical is suggested to be located in the double bond and to give a dimer named butane-1,4-diylidene bis-2H-pyran derivatives [19 ].…”

Section: Methodsmentioning

confidence: 99%

“…This peak is attributed to the oxidation of the formed dimer [19]. The intensity of this wave depends directly on the value of the reverse sweep potential (Figure 2).…”

Section: Electrochemical Reduction Of Methylstyrylpyrylium Perchloratesmentioning

confidence: 96%

“…20) obtained above and the irreversibility of the pyrylium cation reduction peak, are in agreement with the fast electron transfer which takes place at the platinum electrode followed by a chemical reaction. According to the literature [12,19,21] and based on the above results observed from kinetic study, the chemical reaction of the radical pyranyl electrogenerated from pyrylium cation after electron transfer, is a dimerization reaction between radical pyranyl as illustrated in the following mechanism (Scheme 2). …”

Section: Kinetic Investigation: Elucidation Of the Mechanism Of Reducmentioning

confidence: 99%

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Cyclic voltammetry and reduction mechanistic studies of styrylpyrylium perchlorates

Ouédraogo¹,

Tapsoba²,

Guel³

et al. 2012

Bull. Chem. Soc. Eth.

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ABSTRACT. The reduction and oxidation potentials of methylated 4-styrylpyrylium and 6-styrylpyrylium perchlorates have been evaluated using cyclic voltammetry, in comparison to their non-methylated derivatives values. The reduction peak of all studied compounds remained chemically irreversible. The presence of the electron-donating methyl group on pyrylium ring leads to a shift of the styrylpyrylium perchlorates reduction potential towards cathodic values. Kinetic studies on platinum electrodes based on the variation of the peak potential at different scan rates and upon substrate concentrations confirm, in another way, the mechanism of electron transfer.

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Section: Electrochemical Reduction Of Methylstyrylpyrylium Perchloratessupporting

confidence: 82%

Section: Kinetic Investigation: Elucidation Of the Mechanism Of Reducsupporting

confidence: 75%

Section: Methodsmentioning

confidence: 99%

“…This peak is attributed to the oxidation of the formed dimer [19]. The intensity of this wave depends directly on the value of the reverse sweep potential (Figure 2).…”

Section: Electrochemical Reduction Of Methylstyrylpyrylium Perchloratesmentioning

confidence: 96%

Section: Kinetic Investigation: Elucidation Of the Mechanism Of Reducmentioning

confidence: 99%

See 3 more Smart Citations

Cyclic voltammetry and reduction mechanistic studies of styrylpyrylium perchlorates

Ouédraogo¹,

Tapsoba²,

Guel³

et al. 2012

Bull. Chem. Soc. Eth.

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Mehrstufige Redoxsysteme. XLIX. Mitteilung. Mit π‐Systemen substituierte 1,3‐Dimethylidencyclobutane: Synthese und Eigenschaften

Freund

Hünig

1987

Helvetica Chimica Acta

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Multistep Redox Systems. 1,3-Dimethylidenecyclobutanes Substituted by n-Systems: Syntheses and PropertiesAs potential redox systems 1,3-dimethylidenecyclobutanes are synthesized in which the 'em'-methylidene group participates in a cyclopentadienyl (type C4) or cycloheptatrienyl (type A5) system. Benzo-annellated systems are also described. The formation of the C=C bond by the reaction of thioketones (3 and 31) with diazo compounds is extended to 1, 6, 7, 21, and 24, which so far had not been employed. In some cases, intermediate thiiranes can be isolated (e.g. 4) which are smoothly transformed into the target compounds of types C4 and A5 by extrusion of sulfur. The new C=C bonds may be introduced stepwise, thereby allowing the synthesis of unsymmetrically substituted 1,3-dimethylidenecyclobutanes (eg. 20 and 35). Reduction of 10 by Na does not produce bicyclobutanes but compounds 43 and 44 with one dihydrofulvene unit. Es lag daher nahe, die in Heterocyclen eingebauten (Al, A2) oder chinoid-artigen (C3) Methyliden-Gruppen durch in Carbocyclen eingebaute zu ersetzen, die beim moglichen Ubergang in das Bicyclobutan-System genugend Aromatisierungsenergie gewin- Einleitung

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Mehrstufige reversible Redoxsysteme, XLII. [2 + 2]‐Photocycloadditionen von α‐Styrylpyrylium‐Salzen zu 4,4′‐(1,3‐Cyclobutandiyl)bis(pyrylium)‐Salzen sowie deren thermische und baseninduzierte Cycloreversionen

Hesse

Hünig

1985

Liebigs Ann. Chem.

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Die synthetisierten farbigen a-Styrylpyrylium-SaIze 2, 4 und 6 werden grdBtenteils im kristallinen Zustand zu den farblosen Cyclobutanen 7, 8 und 9 photodimerisiert (inverse Photochrornie), deren r-ctt-Konfiguration nachgewiesen wird. Bestrahlung von 2h in Losung erzeugt u. a. das unerwartete Bispyrylium-Salz 10. Differentialkalorimetrie (DSC) weist bei einigen a-Styrylpyryliurn-Salzen eine Modifikationsanderung nach, die bei 6d die Photodimerisierung verhindert. Thermische Cycloreversion (DSC) der Cyclobutane erfolgt zum Teil bei ungewohnlich niedriger Ternperatur: 7c (101"C), 7 b (148"C), 7d (160-180OC). Die Umwandlung im festen Zustand 2 c e 7 c ist vollig reversibel. Die Cyclobutane 7, 8 und 9 erleiden auch eine baseninduzierte (Redox-)Cycloreversion zu 2 , 4 u n d 6 , wahrend rasche zweifache Deprotonierung die Bis(pyrylen)-cyclobutane 22, 23 und 24 erzeugt. Multistep Reversible Redox Systems, XLIII). -12 + 21 Photocycloadditions of a-Styrylpyrylium Salts to 4,4'-(1,3-Cyclobutanediyl)bis(pyrylium) Salts and their Thermal and Base-induced CycloreversionsMost of the synthesized colored a-styrylpyrylium salts 2, 4, and 6 are photodimerized in the crystalline state to give colorless cyclobutanes 7, 8, and 9 (inverse photochromism), the r-ctt configuration of which is proved. Irradiation of 2h in solution produces among other products the unexpected bispyrylium salt 10. By differential scanning calorimetry (DSC) change of crystal modification of some a-styrylpyrylium salts can be seen. This change prevents 6 d from photodimerization. Thermal cycloreversion (DSC) of the cyclobutanes partly occurs at unusually low temperatures: 7c (101 "C), 7b (148'C), 7 d (160-18OOC). The solid-state transformation 2 c e 7c is completely reversibel. Cyclobutanes 7,' 8, and 9 suffer from base-induced (redox) cycloreversion, however, rapid two-fold deprotonation produces the bis(pyry1ene)cyclobutanes 22, 23, and 24.Eine ausfuhrliche Untersuchung an a-Styrylpyridinen undloder a-St yrylpyridiniumSalzen zeigte, da0 ihre [2 + 2]-Photocycloadditionen im festen Zustand und in Ldsung in diffiziler Weise vom Substitutionsmuster, vom Ladungszustand und vom Gegen-Ion abhangen3). Daruber hinaus wurden bei Photoreaktionen in Ldsung in unterschiedlichem AusmaR Nebenreaktionen beobachtet und zwar au0er cis/trans-Isomerisierungen in den Edukten und Produkten vor allem Solvensadditionen und R e d~k t i o n e n~) . Die

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Mehrstufige reversible Redoxsysteme, XLIII. Voltammetrie von α‐Styrylpyrylium‐Salzen, (1,3‐Cyclobutandiyl)‐und (1,3‐Cyclobutandiyliden)bis(pyrylium)‐Salzen

Cited by 8 publications

References 14 publications

Cyclic voltammetry and reduction mechanistic studies of styrylpyrylium perchlorates

Cyclic voltammetry and reduction mechanistic studies of styrylpyrylium perchlorates

Mehrstufige Redoxsysteme. XLIX. Mitteilung. Mit π‐Systemen substituierte 1,3‐Dimethylidencyclobutane: Synthese und Eigenschaften

Mehrstufige reversible Redoxsysteme, XLII. [2 + 2]‐Photocycloadditionen von α‐Styrylpyrylium‐Salzen zu 4,4′‐(1,3‐Cyclobutandiyl)bis(pyrylium)‐Salzen sowie deren thermische und baseninduzierte Cycloreversionen

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