Influence of Electron Delocalization in Heterocyclic Core Systems on the Electrochemical Communication in 2,5-Di- and 2,3,4,5-Tetraferrocenyl Thiophenes, Furans, and Pyrroles

Abstract

A series of 2,5-di- and 2,3,4,5-tetraferrocenyl-substituted thiophenes, furans, and pyrroles were synthesized using the Negishi C,C cross-coupling protocol. The electronic and electrochemical properties of these compounds were investigated by cyclic voltammetry (CV), square wave voltammetry (SWV), and in situ UV-vis/NIR spectroscopy. The molecular structures of 2,5-diferrocenyl furan and 2,3,4,5-tetraferrocenyl-1-methyl-1H-pyrrole in the solid state are discussed. The ferrocenyls could sequentially be oxidized giving two or four reversible responses for the appropriate di- or tetraferrocenyl-substituted heterocyclic molecules. The observed ΔE°' values range between 186 and 450 mV. The NIR measurements confirm electronic communication as intervalence charge transfer (IVCT) absorptions were found in the corresponding mono- and in case of the tetraferrocenyl compounds also in the dicationic species. All compounds, except tetraferrocenyl thiophene (a class I system), were classified as class II systems according to Robin and Day. They show a linear relationship between ΔE°' and the IVCT oscillator strength f which could be shown for the first time in organometallic chemistry. This was possible because the series of molecules exhibit analogous geometries and hence, similar electrostatic properties. This correlation was confirmed by electro- and spectro-electrochemical measurements. Within these studies a new approach for the estimation of the effective electron transfer distances r(ab) is discussed.

Ferrocenylsubstituierte Metallacyclen des Titanocens – Oligocyclopentadienylkomplexe mit vielversprechenden Eigenschaften

“…[4] Die Besonderheit dieser Verbindungen wegen ihrer mçglichen Verwendung in der Elektronik, Optik und Katalyse wurde herausgestellt. ¾hnliche interessante Molekülstrukturen zeigen Verbindungen wie Hexakis(4-ferrocenylphenyl)benzol (C 6 (C 6 H 4 Fc) 6 ), Hexakis(ferrocenylethinyl)benzol (C 6 (C CFc') 6 , Fc' = substituiertes Ferrocenyl) und [(FeCp) 3 (trindenyl)]. [5] Perferrocenylsubstituierte fünf-gliedrige Heterocyclen ( c C 4 Fc 4 X; X = O, S, NR), die erstmals 2011 vorgestellt wurden, sind weitere Beispiele reizvoller Verbindungen.…”

“…[5] Perferrocenylsubstituierte fünf-gliedrige Heterocyclen ( c C 4 Fc 4 X; X = O, S, NR), die erstmals 2011 vorgestellt wurden, sind weitere Beispiele reizvoller Verbindungen. [6] Ihre interessanten elektronischen Eigenschaften wurden intensiv mittels spektroelektrochemischer Messungen untersucht.…”

“…Soweit uns bekannt, gibt es keine ferrocenylsubstituierten Cumulene, die strukturell untersucht wurden. Es existieren jedoch Komplexe verschiedener Metallfragmente ({M 2 (CO) 6 }, M = Fe, Ru; {W(CO) 3 } (unter Dimerisierung) und {RuCpBr}) mit 1,4-Diferrocenylbuta-1,3-dien. [17] Außerdem wurden dreikernige Metallcarbonyle beschrieben (M = Co, Ru, Os), die an FcC CC CFc koordinieren, wobei jedoch keine gespannten Metallacyclen gebildet werden.…”

Fabrication of a porphyrin-based electrochemical biosensor for detection of nitric oxide released by cancer cells

“…The redox behavior of the synthesized 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrin (1) [40][41][42][43][44][45][46][47]. The cyclic voltammetry measurements were performed at 25°C at varied scan rates.…”

Ferrocenes Bridged by Ethylenediamino Thiophene: Varying Charge Transfer Properties in a Series of 3,4-Di-N-substituted 2,5-Diferrocenyl Thiophenes

“…27,35,38,53,54 Within this context, the electronic coupling in the corresponding mixed-valent states varies strongly with the electronic structure of the respective species. [29][30][31][32][33]38,55 It was recently shown for α,α′-diferrocenyl thiophenes that electron-withdrawing groups on the ferrocenyls in combination with an electron-donating ethylenedioxy unit on the thiophene bridge (EDOT) enforces the electronic coupling between the iron-based redox centers in the mixedvalent state. 30,37 In continuation of this work, we report herein the synthesis of diferrocenyl diamino thiophenes in a series of 3,4-di-Nsubstituted 2,5-diferrocenyl thiophenes (Figure 1) with the aim of improving the electronic interaction between the organometallic termini over their bridging unit.…”