Ferrocenylcarboxylic Acids Research Articles

Oxidation and reduction data of four subphthalocyanines with axially coordinated ferrocenylcarboxylic acids.

Redox data obtained from cyclic voltammetry experiments of the FeII/III and ring-based oxidation and reductions of subphthalocyanines containing a ferrocenylcarboxylic acid as axial ligand, is presented in this data in brief article. The FeII/III oxidation of ferrocenylsubphthalocyanines which containing the electron-withdrawing fluorine atoms at the peripheral and non-peripheral positions, are ca. 0.100 V more positive than FeII/III oxidation of ferrocenylsubphthalocyanines containing hydrogens at the peripheral and non-peripheral positions. For more insight into the reported data, see the related research article “Redox and photophysical properties of four subphthalocyanines containing ferrocenylcarboxylic acid as axial ligands” [1].

Synthesis, Spectroscopy, Electrochemistry and DFT of Electron-Rich Ferrocenylsubphthalocyanines.

A series of novel ferrocenylsubphthalocyanine dyads Y-BSubPc(H)12 with ferrocenyl-carboxylic 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 (−1.871 V vs. 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.

Redox and Photophysical Properties of Four Subphthalocyanines Containing Ferrocenylcarboxylic Acid as Axial Ligands.

Four new ferrocenylsubphthalocyanines Y-BSubPc, with ferrocenylcarboxylic acid YH = Fc-CH2-CH2-COOH (1) or Fc-CH═CH-COOH (2) in the axial Y position, were synthesized with a 40% yield. The axial ferrocenylcarboxylic acid moiety did not have a significant influence on the position of the Q bands maxima of the UV/vis spectra of the ferrocenylsubphthalocyanines or on the 1H NMR position of the ring proton peaks of Y-BSubPc(H12) or on the 19F NMR position of the ring F peaks of YSubPc(F12), relative to their respective parent compounds Cl-BSubPc(H12) 3 and Cl-BSubPc(F12) 4, containing axial chlorine. Very weak metal-to-ligand-charge-transfer bands (MLCT) in the near-IR region were observed. An electrochemical study utilizing cyclic voltammetry showed that electronic communication exists between ferrocene on the axial ferrocenylcarboxylic acid and the π-electrons of the macrocycle of the ferrocenylsubphthalocyanine (Fc(CH2)2COO)-BSubPc(H)12,5, (Fc(CH)2COO)-BSubPc(H)12, 6, (Fc(CH2)2COO)-BSubPc(F)12, 7, and (Fc(CH)2COO)-BSubPc(F)12, 8. The Fe group of the ferrocenyl-containing axial ligand is involved in the first reversible oxidation process, followed by a second oxidation localized on the subphthalocyanine ligand. The fluorine ring substituents in SubPcs 7 and 8 caused the ferrocenyl oxidation to shift more positive by ca. 0.1 V, compared to SubPcs 5 and 6 without fluorine. Density functional theory (DFT) calculations provided further insight into the properties of these novel ferrocenylsubphthalocyanines. The neutral species of SubPcs 5-8 have LUMOs with mainly π-ring character and HOMOs with mainly iron-d character, confirming ring-based reduction, metal-based Fe(II) to Fe(III) oxidation, as well as weak MLCT in the near-IR region. Further DFT optimization of the cation (oxidized) species was essential to verify the second ring-based oxidation.

Solvent and substituent effect on electrochemistry of ferrocenylcarboxylic acids

The redox properties of six ferrocenyl carboxylic acids (1–6) in dichloromethane and acetonitrile are compared. The formal reduction potential of Fe of the ferrocenyl group in these carboxylic acids occur ca. 0.1 V more positive in DCM than in CH3CN. The carboxylic group is directly connected to ferrocenyl, or by an ethene group, or by an alkyl chain of varying length. The length of the alkyl chain separating the two groups affected the formal reduction potential of Fe of the ferrocenyl group. The formal reduction potential was also affected by the electron-withdrawing carbonyl group. The extent of the effect depended on whether the carbonyl group was directly bound to a ferrocenyl moiety or, isolated by an sp3 hybridized carbon atom backbone (-CH2-CH2-) or a non-isolated sp2 hybridized carbon atom backbone (-CH=CH-). The results obtained were further validated by density functional theory (DFT) calculations on ferrocenyl carboxylic acids (1–6) as well as selected substituted ferrocenyl compounds from literature. A linear relationship between the formal reduction potential of substituted ferrocenes and DFT calculated HOMO energies were obtained.

How many ferrocene units of multi-ferrocenyl complexes can react with the electrode?

Ferrocenylcarboxylic acid Fe, Co, and Ni complexes were synthesized as model complexes to investigate how many ferrocene units of multi-ferrocenyl system can react with the electrode. The molecular structures of model complexes were characterized by X-ray single-crystal diffraction, the diffusion coefficient of the complexes and ferrocene was determined by the diffusion-ordered spectroscopy and Einstein–Stokes equation, the electrode reaction numbers of ferrocene units were determined by cyclic voltammetry and the Randles–Sevcik equation. A model of electrode reaction of multi-ferrocenyl system was proposed in this paper, which was used to explore how many ferrocene units of multi-ferrocenyl complexes can react with the electrode.

Effect of Nitrogen-Containing Bases on Oxidation of Ferrocenylboric and Ferrocenylcarboxylic Acids with Hydrogen Peroxide in Water and Water–Acetonitrile Mixed Solvent

The effect of triethylamine and pyridine on the kinetics and mechanism of ferrocenylboric and ferrocenylcarboxylic acids oxidation with hydrogen peroxide in water and aqueous-organic media has been studied. The addition of amines has accelerated the oxidation of ferrocenylboric acid both by hydrogen peroxide and by oxygen. Triethylamine has slowed down the oxidation of ferrocenylacetic acid and stabilized the formed zwitter-ion Fc+CH2COO–. Ferrocenylcarboxylic acid has not been oxidized by H2O2. The mechanism of the reaction has been suggested.

Synthesis, characterization and photophysical properties of novel azole derivatives.

This paper concerns the design, synthesis, structural characterization, thermal stability evaluation and fluorescence properties of novel triazolothiadiazole derivatives. The target compounds 6a-e were synthesized by condensing 4-amino-3-(4-methoxybenzyl)-1H-1,2,4-triazole-5 (4H)-thione (5) with biphenyl, naphthyl, p-terphenyl, pyrenyl and ferrocenyl carboxylic acid in the presence of phosphorous oxychloride. The structures of newly synthesized compounds were characterized by IR, (1)H NMR and (13)C NMR analysis. The photophysical properties of synthesized compounds were measured in a variety of organic solvents of variable polarities. Spectral properties of the compounds were highly dependent on the nature of the substituent and coupling components attached to the triazolothiadiazole skeleton as well as slightly affected by the solvent polarities. Correlation of the absorption spectra and fluorescence emission response of 6a-e with the substituent revealed that the fluorescent properties can easily be tuned by varying conjugation length of side coupled groups. The newly synthesized derivatives represent a new type of fluorescent materials with efficient visible absorption and surpassing brightness which could be a promising candidate for bioimaging, photonic applications, organic light emitting diodes and dye sensitized solar cells.

Features of autoxidation of ferrocenylcarboxylic acid and its methyl ester in organic solvents in the presence of Brønsted acids

We have studied the autoxidation of ferrocenecarboxylic acid and its methyl ester in organic solvents in the presence of perchloric and trifluoroacetic acids. Based on the results of kinetic studies and data on the composition of the reaction products, we suggested the possible reaction mechanisms, including those of molecular and radical-chain macrostages of the process. The features of the solvent influence on the rate of oxidation of metallocomplexes and the reasons for its extreme dependence with increasing concentration of perchloric acid are discussed.

A 1D Schiff base zinc polymer as a versatile metallo-ligand for the synthesis of polynuclear zinc cages

The 1D polymeric Schiff base zinc complex, [LZn(2)Et(2)](n), where LH(2) = (NN'-ethylene-bis(4-iminopentan-2-one)) has been demonstrated as a useful synthetic metallo building block for the synthesis of homo and heteronuclear zinc cages. The reaction of [LZn(2)Et(2)](n) with CdI(2) afforded the hetero-nuclear cage, 1, [L(2)Zn(4)(Et)(2)CdI(4)], while reaction with HgI(2) afforded a hexanuclear zinc cage, [L(2)Zn(6)(Et)(4)(μ(4)O)(μ(3)OEt)I], 2. The versatility of [LZn(2)Et(2)](n) as a metallo building block is demonstrated through the reaction with ferrocenyl carboxylic acid, affording the ferrocenyl supported zinc cage, [L(2)Zn(8)(FcCO(2))(4)(Et)(2)(OEt)(2)(μ(4)O)(2)], 3, while the reaction with Er(III) acetate afforded the decanuclear zinc cage, [L(3)Zn(10)(μ(4)O)(4)(Et)(6)], 4.

Preparation of ferrocenyl imidazolines using bis(triphenyl)oxodiphosphonium trifluoromethanesulfonate

An efficient synthesis of ferrocenyl imidazolines starting from ferrocenyl carboxylic acids has been developed. Bis(triphenyl)oxodiphosphonium trifluoromethanesulfonate was used to convert smoothly ferrocenyl carboxylic amides bearing an amine side chain, derived from ferrocenyl carboxylic acids and 1,2-diamines, to their corresponding ferrocenyl imidazolines.

Ferrocenyl glycopeptides as electrochemical probes to detect autoantibodies in multiple sclerosis patients' sera

Glycopeptide analogues of CSF114(Glc), modified at N-terminus with new ferrocenyl carboxylic acid and a new ferrocenyl-thiphosphino amino acid, were used to implement a new electrochemical biosensor for autoantibody detection in multiple sclerosis. The ferrocenyl moiety of these "electrochemical probes" did not affect autoantibody recognition both in SP-ELISA and in inhibition experiments. By electrochemical monitoring the interactions of the modified peptides Fc-CSF114(Glc) and 4-FcPhP(S)Abu-CSF114(Glc) with the autoantibodies, we demonstrated that autoantibodies could be detected with a sensitivity comparable to ELISA method. The new electrochemical probes can be proposed to characterize autoantibodies as biomarkers of multiple sclerosis by a simple, rapid, and reproducible cyclic voltammetry-based diagnostic methodology.

Preparation of Di-, Tri-, and Tetra-Substituted Functionalized Ferrocenes via Magnesium Organometallics

Ferrocenyl carboxylic acid derivatives were metalated with TMPMgCl·LiCl, leading after reaction with electrophiles to 1,2-disubstituted ferrocenes. Further metalation of these disubstituted ferrocenes with TMPMgCl·LiCl afforded trisubstituted ferrocenes. A 1,2,3,4-tetrasubstituted ferrocene derivative could also be prepared in this way.

Synthesis and electrochemical properties of a series of ferrocene-containing alcohols

A series of primary ferrocenylalcohols, Fc–(CH 2) m –OH with m = 1–4 and Fc = ferrocenyl, was synthesised by reduction of the appropriate ferrocenylcarboxylic acids, Fc–(CH 2) n –COOH ( n = 0–3) and the ester methyl 4-ferrocenylbutanoate with LiAlH 4, the reduction of the γ-ketoacid ferrocylpropanoic acid, Fc–CO–(CH 2) 2–COOH, with AlCl 3/LiAlH 4, and the reduction of ferrocenylcarboxaldehyde, FcCHO, with NaBH 4. The secondary ferrocenyl alcohols CpFe(C 5H 4–CH(OH)–CH 3) and Fe(C 5H 4–CH(OH)–CH 3) 2 were obtained by NaBH 4 reduction of acetyl and diacetyl ferrocene. The different reduction methods are compared. The electrochemistry of the alcohols was studied by cyclic voltammetry in CH 3CN/0.1 M N( n Bu) 4PF 6 utilising a platinum working electrode. The ferrocenyl group showed reversible electrochemistry with the formal reduction potential ( E o′ versus Fc/Fc +) of the ferrocenyl group inversely proportional to side chain length. The influence of the side chain length on E o′ was more pronounced for the acids because the electron-withdrawing properties of the carbonyl group is stronger than that of the alcohol group. Ion pairing was found to play a major role in the electrochemical behaviour of ferrocenylmethanol, Fc–CH 2–OH.

Self-assembly of ferrocene-functionalized perylene bisimide bridging ligands with PtII corner to electrochemically active molecular squares.

Ferrocenyl-substituted N,N'-di(4-pyridyl)perylene bisimide ligands have been synthesized by the coupling reaction of hydroxyphenoxy-perylene bisimides with ferrocenyl carboxylic acids. By means of metallosupramolecular self-assembly, hitherto unprecedented multiredox active dendritic molecular squares with 16 ferrocene groups positioned in the bridging ligands are prepared from the perylene bispyridyl imide ligands and [Pt(dppp)][(OTf)(2)] (dppp = 1,3-bis(diphenylphosphano)propane; OTf = trifluoromethanesulfonate) corner in high yield. The isolated metallosupramolecular squares were characterized by elemental analysis, (1)H, (31)P[(1)H] NMR, and UV/vis spectroscopy. The electrochemical properties of the ligands and squares are investigated by cyclic voltammetry as well as spectroelectrochemistry. The results obtained show that the redox behavior of ferrocene units is influenced by the square superstructure. Furthermore, redox titration of free ligand and corresponding molecular square with the one-electron oxidant thianthrenium pentachloroantimonate reveals that ferrocene groups in these structures may be oxidized completely by this oxidant, and highly charged species generated through oxidation of ferrocenyl groups in molecular square cause decomposition of the assembly due to pronounced Coulombic repulsion.

Synthesis and characterization of 1-ferrocenecarboxysilatranes and crystal structures of FcC(CH 3)CHCOOSi(OCH 2CH 2) 3N and p-FcC 6H 4COOSi(OCH 2CH 2) 3N

A series of novel silatranes containing ferrocenyl carboxylate were obtained by the reaction of 1-ethoxysilatrane with ferrocenyl carboxylic acids, and characterized by elemental analysis, IR and 1H-NMR. The crystal structure of FcC(CH 3)CHCOOSi(OCH 2CH 2) 3N and p-FcC 6H 4COOSi(OCH 2CH 2) 3N was determined by X-ray diffraction. The SiN distances of the two compounds are 2.065 and 2.052 Å, respectively. Both the bond distances are shorter than that of 1-alkyl or 1-alkoxysilatranes and close to that of 1-halosilatranes. The antibacterial activity of p-FcC 6H 4COOSi(OCH 2CH 2) 3N was determined.

Controlling the acidity of the carboxylic group by a ferrocene based redox switch

The pH dependent oxidation behaviour of the ferrocene subunit in ferrocenylcarboxylic acids of formula Fc(CH 2) nCOOH ( n = 0, 1, 2) has been investigated through differential pulse voltammetry experiments in 4:1 acetonitrile/water solutions. Different voltammetric responses have been obtained depending whether the pH has been varied through a buffer (a single peak, whose E 1/2 value decreases with the increasing pH) or through an acid-base titration (two distinct peaks, the less anodic corresponding to the oxidation of the FcCOO − species, the more anodic corresponding to the oxidation of the FcCOOH species, whose relative intensities vary with the pH). The electrochemically determined pK a values for the Fc(CH 2) nCOOH and [Fc +](CH 2) n COOH forms indicate that the Fc-to-Fc + oxidation process makes the acidity of the proximate carboxylic group increase. Such a switching effect, electrostatic in nature, decreases as n increases.

Synthesis and characterization of water-soluble polyaspartamide-ferrocene conjugates for biomedical applications

Polymer-ferrocene conjugates are synthesized from the polyamide1, poly-α,β-dl-[N-(3-(morpholin-4-yl)propyl)aspartamide-co-N-(2-aminoethyl)aspartamide, through coupling of amino side groups with the carboxyl function in a number of ferrocenylcarboxylic acids, including ferrocenoic acid, ferrocenylacetic acid, 3-ferrocenylpropanoic acid, 3-ferrocenylbutanoic acid, 4-ferrocenylbutanoic acid, and 4-ferrocenyl-4-hydroxypentanoic acid. The ferrocene complex has been chosen for conjugation by virtue of the cytotoxic properties observed with some of its derivatives. The coupling reactions, mediated by HBTU (O-benzotriazolyl-N,N,N′N′-tetramethyluronium hexafluorophosphate), are brought about inN,N-dimethylformamide solution and lead to degrees of substitution in the range of 25–95%. The resulting conjugates2, fractionated by dialysis in tubing with a 12,000–14,000 molecular mass cutoff and collected in the solid state by freeze-drying, are completely soluble in water after isolation and retain this property in frozen aqueous solutions. Preliminary electrochemical data are reported, indicating a decreasing (i.e., less positive) potential with increasing length of the aliphatic, electron-donating connecting link between the ferrocene and the carboxamide anchoring group. The 4-ferrocenylbutanoyl substituent is associated with the least positive potential of those structures investigated and, hence, should provide conjugates with optimalin vivo stability in the ferricenium state. Selected conjugates will be submitted to screening tests for antineoplastic activity.

Electrochemical characterization of some ferrocenylcarboxylic acids

Several carboxy-substituted ferrocene compounds are prepared and investigated by cyclic voltammetry in acetonitrile solution. The half-wave potentials of most of the acids studied (E 1/2=0.34−0.58 V versus s.c.e.) are more positive than that of ferrocene (0.33 V), reflecting a diminished susceptibility to oxidation of these compounds relative to the parent metallocene. Only β-ferrocenylpropionic acid (0.325 V) is effectively identical with the latter in its oxidation behaviour, and γ-ferrocenylbutyric acid (0.31 V) tends to be more readily oxidized. The results are of interest for subsequent chemical oxidation studies of ferrocenylcarboxylic acids.

A new class of semi-synthetic antibiotics: ferrocenyl-penicillins and -cephalosporins

A series of ferrocenyl carboxylic acids has been prepared and condensed, via their acid chlorides or in the presence of N, N′-dicyclohexylcarbodiimide, with both 6-aminopenicillanic acid and 7-aminocephalosporanic acid. Almost all of the ferrocenyl-penicillins and -cephalosporins exhibited antibiotic activity, some being highly active, while others proved to be potent β-lactamase inhibitors.