- Charge-Transfer-to-Solvent Photochemistry of Electrode-Confined Ferrocene- and Cobaltocene-Based Polymers: Photoelectrochemical Reduction of Halocarbons
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Like the metallocenes themselves, metallocene-based polymers exhibit near-UV (280-370 nm) charge-transfer-to-solvent (CTTS) absorption in the presence of CCl4, CHCl3, CH2Cl2, CBr4, and CHBr3.The photoelectrochemistry of charge transfer complexes of two ferrocene-containing polymers and one cobaltocene-containing polymer has been studied.The polymers are poly(2-ferrocenylethyl methacrylate), poly(3-(octamethylferrocenyl)propyl methacrylate), and poly(1,1'-biscobaltocene).Photoexcitation of metallocenes and metallocene-based polymers in the presence of many halocarbons yields oxidation of the metallocene and reduction of the halocarbon.When the metallocene-based polymer is confined to the surface of an electrode that is held at a potential negative of the formal potential of the metallocene, near-UV excitation results in sustained cathodic current in electrolyte solutions containing halocarbons.The wavelength, acceptor, and potential dependences are in accord with a sustained current that is due to a metallocene-to-halocarbon CTTS absorption where the photoprocess results in the reduction of the halocarbon at an electrode potential significantly positive of where electrochemical reduction occurs in the dark.The octamethylferrocene-based system shows a more negative potential onset and a longer wavelength offset of photocurrent than the simple ferrocene-based system, consistent with the electron-releasing nature of the methyl substituents.The onset of photocurrent in the cobaltocene-based system occurs at the most negative potential of the three, consistent with the cobaltocene-based system having the most negative formal potential of the metallocenes studied.
- Tatistcheff, Helen B.,Hancock, Lawrence F.,Wrighton, Mark S.
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- Electrochemical detection of nucleic acids using pentaferrocenyl phosphoramidate α-oligonucleotides
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We report the synthesis of α-oligonucleotides exhibiting five phosphoramidate linkages bearing a ferrocenyl (Fc) moiety. Three different linkers: ethyl, propyl and 4-methyl-1-ethyl-1,2,3-triazol between the ferrocene (Fc) residue and the phosphoramidate f
- Chatelain, Gregory,Meyer, Albert,Morvan, Franois,Vasseur, Jean-Jacques,Chaix, Carole
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- Synthesis, spectroscopy, electrochemistry and DFT of electron-rich ferrocenylsubphthalocyanines
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A series of novel ferrocenylsubphthalocyanine dyads Y-BSubPc(H)12 with ferrocenylcarboxylic acids Y-H = (FcCH2CO2-H), (Fc(CH2)3CO2-H) or (FcCO(CH2)2CO2-H) in the axial position were synthesized from the parent Cl-BSubPc(H)12 via an activated triflate-SubPc intermediate. UV/Vis data revealed that the axial ferrocenyl-containing ligand did not influence the Q-band maxima compared to Cl-BSubPc(H)12. A combined electrochemical and density functional theory (DFT) study showed that Fe group of the ferrocenyl-containing axial ligand is involved in the first reversible oxidation process, followed by a second oxidation localized on the macrocycle of the subphthalocyanine. Both observed reductions were ring-based. It was found that the novel Fc(CH2)3CO2BSubPc(H)12 exhibited the lowest first macrocycle-based reduction potential (-1.871Vvs. Fc/Fc+) reported for SubPcs till date. The oxidation and reduction values of Fc(CH2)nCO2BSubPc(H)12 (n = 0-3), FcCO(CH2)2CO2BSubPc(H)12, and Cl-BSubPc(H)12 illustrated the electronic influence of the carboxyl group, the different alkyl chains and the ferrocenyl group in the axial ligand on the ring-based oxidation and reduction values of the SubPcs.
- Conradie, Jeanet,Swarts, Pieter J.
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supporting information
(2020/07/02)
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- A process for preparing 3 - substituted - 6 - ferrocenyl methylene - 1, 2, 4 - triazolo [3.4 - b] - 1, 3, 4 - thiadiazole method
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The invention relates to a method for preparing 3-substituted-6-ferrocenylmethylene-1,2,4-triazolo[3.4-b]-1,3,4-thiadiazole. The method comprises the following steps: 1) adding A mmol of ferrocenyl acetic acid, B mmol of 3-substituted-4-amino-5-sulfhydryl
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Paragraph 0033; 0042; 0051; 0060; 0069
(2017/11/21)
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- A DFT-Elucidated comparison of the solution-phase and SAM electrochemical properties of short-chain mercaptoalkylferrocenes: Synthetic and spectroscopic aspects, and the structure of Fc- CH2CH2-S-S-CH2CH2-Fc
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Facile synthetic procedures to synthesize a series of difficult-To-obtain mercaptoalkylferrocenes, namely, Fc(CH2)nSH, where n = 1 (1), 2 (2), 3 (3), or 4 (4) and Fc = Fe(n5-C5H5)(n5-C5H4), are reported. Dimerization of 1-4 to the corresponding disulfides 19-22 was observed in air. Dimer 20 (Z = 2) crystallized in the triclinic space group Pi. Dimers 20-22 could be reduced back to the original Fc(CH2)nSH derivatives with LiAlH4 in refluxing tetrahydrofuran. Density functional theory (DFT) calculations showed that the highest occupied molecular orbital of 1-4 lies exclusively on the ferrocenyl group implying that the electrochemical oxidation observed at ca. -15 pa a radical, Fc(CH2)nS, with spin density mainly located on the sulfur. Rapid exothermic dimerization leads to the observed dimers, Fc(CH2)n-S-S- (CH 2)nFc. Reduction of the ferrocenium groups on the dimer occurs at potentials that still showed the ferrocenyl group E = Epa,monomer - Epc,dimer ≤ 78 mV, indicating that the redox properties of the ferrocenyl group on the mercaptans are very similar to those of the dimer. 1H NMR measurements showed that, like ferrocenyl oxidation, the resonance position of the sulfhydryl proton, SH, and others, are dependent on -(CH2)n- chain length. Self-Assembled monolayers (SAMs) on gold were generated to investigate the electrochemical behavior of 1-4 in the absence of diffusion. Under these conditions, δE approached 0 mV for the longer chain derivatives at slow scan rates. The surface-bound ferrocenyl group of the metal-Thioether, Fc(CH)n -S-Au, is oxidized at approximately equal potentials as the equivalent CH2Cl2-dissolved ferrocenyl species 1-4. Surface coverage by the SAMs is dependent on alkyl chain length with the largest coverage obtained for 4, while the rate of heterogeneous electron transfer between SAM substrate and electrode was the fastest for the shortest chain derivative, Fc-CH2-S-Au.
- Lewtak, Jan P,Landman, Marilé,Fernández, Israel,Swarts, Jannie C
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p. 2584 - 2596
(2017/01/16)
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- Reduction of Escherichia coli ribonucleotide reductase subunit R2 with eight water-soluble ferrocene derivatives
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Water soluble ferrocenes [Fe(Cp)(CpL)], where Cp- is the η5-cyclopentadienide ligand and the side chain L is (a) the carboxylic acid group -(CH2)xCO2H with x=0-4 (I-V); (b) the complex x=2 with the β-methylene mono-methyl substituted (VI); (c) the amine hydrochloride derivative with L=CH(Me) NH3+ (VII); and (d) the complex with two Cp rings bridged by the amine hydrochloride -CH(NH3+)CH2CH2- (VIII); have been prepared, and are used as one-equivalent reductants for the active-R2 subunit of Escherichia coli ribonucleotide reductase. Formal reduction potentials E1°′ (25°C) of the carboxylates of acids I-VI in 20 mM NaOH, and of the amine hydrochlorides VII and VIII in water were determined by cyclic voltammetry, and are in the range 0.308-0.550 V versus nhe, I=0.100 M (NaCl). Second-order rate constants k12 (25°C) for the reduction of active-R2 were determined by UV-Vis spectrophotometry, and are in the range 0.15-0.50 M-1 s-1 at I=0.100 M. A free-energy plot of logk12 versus E°′ values gives no clearcut unidirectional trend. Since from present information the electron self-exchange rate constant for the [Fe(Cp)2]+/[Fe(Cp)2] couple is favourable (>7×106 M-1 s-1 in methanol at 25°C), it would appear that electron-transfer from the ferrocenes via Trp-48, Asp-237, His-118 to the FeIII2 site on R2 is much slower than expected, and smaller than with the organic radical reductants previously studied. Electron-transfer from some other position on the protein surface to the Tyr· is considered as an alternative.
- Liu, Aimin,Leese, David N.,Swarts, Jannie C.,Sykes
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