Ferrocenedicarboxylic Acid Research Articles

PH-switchable bioelectrocatalysis based on layer-by-layer films assembled through specific boronic acid-diol recognition

Phenylboronic acid (PBA) moieties are grafted onto the backbone of poly(acrylic acid) (PAA), forming the PAA-PBA polyelectrolyte. The PAA-PBA and polysaccharide dextran (Dex) are then assembled layer-by-layer (LbL) into {PAA-PBA/Dex} n films on electrode surface through the boronic acid-diol specific recognition between them. The cyclic voltammetric response of ferrocenedicarboxylic acid (Fc(COOH) 2) at the film electrodes is sensitive to the environmental pH. At pH 5.5, the CV peak currents are quite large, and the films are at the “on” state; at pH 8.0, however, the CV response is significantly suppressed with the films at the “off” state. This pH-sensitive on–off property of the films toward the probe can be used to switch the bioelectrocatalysis of glucose mediated by Fc(COOH) 2 in the present of glucose oxidase (GOD) in solution by changing the surrounding pH. Furthermore, PAA-PBA and the glycoenzyme GOD are also assembled into {PAA-PBA/GOD} n LbL films by the boronic acid-diol specific interaction between them, so that the immobilization of the enzyme on electrodes can be realized. The {PAA-PBA/GOD} n films also show pH-sensitive on–off behavior in bioelectrocatalysis of glucose with Fc(COOH) 2 as the mediator. This model system may open a new way to establish a foundation for fabricating pH-responsive biosensors based on enzymatic electrocatalysis.

Simultaneous determination of levodopa, NADH, and tryptophan using carbon paste electrode modified with carbon nanotubes and ferrocenedicarboxylic acid

The redox response of a modified carbon nanotube paste electrode of ferrocenedicarboxylic acid was investigated. Cyclic voltammetry, differential pulse voltammetry, and chronoamperometry were used to investigate the electrochemical behavior of levodopa (LD) at modified electrode. Under the optimized conditions (pH 5.0), the modified electrode showed high electrocatalytic activity toward LD oxidation; the overpotential for the oxidation of LD was decreased by more than 190 mV, and the corresponding peak current increased significantly. Differential pulse voltammetric peak currents of LD increased linearly with its concentrations at the range of 0.04 to 1,100 μM, and the detection limit (3σ) was determined to be 12 nM. The diffusion coefficient \( \left( {D = {9}.{2} \times {1}{0^{ - {6}}}{\hbox{c}}{{\hbox{m}}^2}/{\hbox{s}}} \right) \) and transfer coefficient (α = 0.49) of LD were also determined. Mixture of LD, NADH, and tryptophan (TRP) can be separated from one another by differential pulse voltammetry. These conditions are sufficient to allow determination of LD, NADH, and TRP both individually and simultaneously. The modified electrode showed good reproducibility, remarkable long-term stability, and especially good surface renewability by simple mechanical polishing. The results showed that this electrode could be used as an electrochemical sensor for determination of LD, NADH, and TRP in real samples such as urine and water samples.

Dual-Switchable Bioelectrocatalysis Synergistically Controlled by pH and Perchlorate Concentration Based on Poly(4-vinylpyridine) Films

Poly(4-vinylpyridine) (P4VP) films were electropolymerized on a pyrolytic graphite (PG) electrode surface. The cyclic voltammetric (CV) response of ferrocenedicarboxylic acid (Fc(COOH)(2)) at P4VP film electrodes was very sensitive to the pH and perchlorate (ClO(4)(-)) concentration in testing solutions. Fc(COOH)(2) was at the "on" state with a relatively large CV oxidation peak current for the films at pH 4.0 but showed the "off" state with significantly suppressed CV response at pH 7.0. The reversible ClO(4)(-) concentration-sensitive on-off property of P4VP films toward Fc(COOH)(2) at pH 4.0 was also observed. In particular, the influence of pH and ClO(4)(-) concentration on the on-off behavior of the system is not independent or separate but synergetic or cooperative, and the electrostatic interaction between the films and the probe plays a predominant role in deciding the pH- and/or ClO(4)(-) concentration-dependent behavior for the system. The dual-responsive property of the P4VP films toward Fc(COOH)(2) could also be used to control the bioelectrocatalysis of glucose by glucose oxidase. This synergetic-triggered bioelectrocatalysis on the basis of the intelligent interface system may establish a foundation for fabricating novel multiple factor-controllable biosensors based on enzymatic electrocatalysis.

PH-controllable bioelectrocatalysis of glucose by glucose oxidase loaded in weak polyelectrolyte layer-by-layer films with ferrocene derivative as mediator

Oppositely charged poly(allylamine hydrochloride) (PAH) and hyaluronic acid (HA) were assembled into {PAH/HA} n layer-by-layer (LBL) films on pyrolytic graphite (PG) electrodes. Glucose oxidase (GOD) in solution was then loaded into the films, designated as {PAH/HA} n –GOD. When the {PAH/HA} n –GOD film electrodes were placed in pH 5.0 buffers containing ferrocenedicarboxylic acid (Fc(COOH) 2) and glucose, a well-defined and large cyclic voltammetric (CV) oxidation wave of glucose catalyzed by GOD immobilized in the films and mediated by Fc(COOH) 2 in solution was observed. However, when the films were placed in pH 9.0 buffers containing the same amount of Fc(COOH) 2 and glucose, the electrocatalytic response was quite small. The bioelectrocatalysis for the film system was at the “on” state at pH 5.0 and at the “off” state at pH 9.0. This pH-sensitive “on–off” behavior was reversible and could be repeated for several times. The possible mechanism of the pH-switchable bioelectrocatalysis was explored and discussed, and should be mainly attributed to the different electrostatic interaction between Fc(COOH) 2 and the films at different pH. This work provides a novel model to realize pH-controllable bioelectrocatalysis based on the enzyme-loaded LBL assembly films, and may guide us to develop the tunable electrochemical biosensors based on electrocatalysis with immobilized enzymes.

Electrocatalytic and Simultaneous Determination of Phenylhydrazine and Hydrazine Using Carbon Paste Electrode Modified With Carbon Nanotubes and Ferrocenedicarboxylic Acid

Electrocatalytic and Simultaneous Determination of Phenylhydrazine and Hydrazine Using Carbon Paste Electrode Modified With Carbon Nanotubes and Ferrocenedicarboxylic Acid

Preparation of Novel Ferrocene-Based Shell Cross-Linked Thermoresponsive Hybrid Micelles with Antitumor Efficacy

The shell cross-linked (SCL) thermoresponsive hybrid poly(N-isopropylacrylamide-co-aminoethyl methacrylate)-b-polymethyl methacrylate (P(NIPAAm-co-AMA)-b-PMMA) micelle consisting of a cross-linked thermoresponsive hybrid shell and a hydrophobic core domain was fabricated via a two-step process: micellization of P(NIPAAm-co-AMA)-b-PMMA in aqueous solution followed by cross-linking of the hydrophilic shell layer via the amidation reaction between the amine groups of AMA units and the carboxylic acid functions of 1,1'-ferrocenedicarboxylic acid. The SCL micelle showed reversible dispersion/aggregation in response to the temperature cycles through the lower critical solution temperature (LCST) of the thermoresponsive hybrid shell at around 36 degrees C, observed by turbidity measurements and dynamic light scattering (DLS). Besides the usage as an inorganic difunctional cross-linker, the inorganic ferrocene segment further endowed the SCL hybrid micelle with the antitumor efficacy, namely, the resulting SCL micelle exhibited a remarkable cytotoxic effect for HeLa cells with a very low IC50. The results showed that the SCL hybrid micelle developed in this study could be potentially used as an antitumor agent, which is unique compared to the conventional tumor therapy by using the antitumor drug loaded in the micellar core.

Novel organometallic aromatic polyester based on ferrocene

A novel polyester containing ferrocenyl was prepared by low-temperature interface polycondensation of 1,1′-ferrocenedicarboxylic acid chloride with 4-(4-hydroxyphenyl)-2,3-phthalazin-1-one(DHPZ), which is a twisted non-coplanar heterocyclic bisphenol-like monomer. The newly generated polymer was evaluated based on characterization of its solubility, viscosity measurements, elemental analysis, FTIR spectroscopy, differential scanning calorimetric and thermogravimetric studies.

PH-Controllable Bioelectrocatalysis Based on “On−Off” Switching Redox Property of Electroactive Probes for Spin-Assembled Layer-by-Layer Films Containing Branched Poly(ethyleneimine)

Weak polybase branched poly(ethyleneimine) (BPEI) and strong polyacid poly(styrenesulfonate) (PSS) were assembled into BPEI/{PSS/BPEI}(n) layer-by-layer (LBL) films on electrodes by electrostatic interaction between them with spin-coating approach. The cyclic voltammetric (CV) response of ferrocenedicarboxylic acid (Fc(COOH)(2)) at BPEI/{PSS/BPEI}(n) film electrodes was very sensitive to the pH of the testing solutions. At pH 4.0, the probe showed a well-defined CV peak pair with relatively large peak currents for the films, while, at pH 7.0, the CV response was significantly depressed. By switching the film electrodes in buffers between pH 4.0 and 7.0, the CV peak currents changed periodically between a relatively high value at the "on" state and a very low value at the "off" state, indicating that the pH-sensitive "on-off" switching function of the films toward the probe is reversible. A series of comparative experiments indicates that the electrostatic interaction between the films and the probe plays a predominant role in deciding the pH-sensitive behavior of the films. This pH-dependent property of the films could be used to control or modulate the bioelectrocatalysis of glucose by glucose oxidase (GOD) with Fc(COOH)(2) as the mediator by changing the surrounding pH. This "smart" bioelectrocatalytic film system may establish a foundation for fabricating novel pH-controllable electrochemical biosensors.

Electrocatalytic Oxidation and Voltammetric Determination of Hydrazine by 1,1′-Ferrocenedicarboxylic Acid at Glassy Carbon Electrode

Electrocatalytic Oxidation and Voltammetric Determination of Hydrazine by 1,1′-Ferrocenedicarboxylic Acid at Glassy Carbon Electrode

Modified multiwall carbon nanotubes paste electrode as a sensor for simultaneous determination of 6-thioguanine and folic acid using ferrocenedicarboxylic acid as a mediator

A multiwall carbon nanotubes modified electrode was prepared using ferrocenedicarboxylic acid as a mediator to be used as an amperometric sensor for the simultaneous determination of 6-thioguanine and folic acid. The electrochemical behaviors of the compounds at this modified electrode were studied using cyclic voltammetry, differential pulse voltammetry, and electrochemical impedance spectroscopy. The results indicated that the chemically modified electrode exhibited an efficient electrocatalytic activity towards the oxidation of 6-thioguanine and folic acid at pH 9.0. Using chronoamperometry, the catalytic reaction rate constant was calculated at 8.2 × 10 2 (mol L −1) −1 s −1. The catalytic peak current was linearly dependent on 6-thioguanine and folic acid concentrations in the range of 0.01–100 μmol L −1 6-thioguanine and 4.6–152 μmol L −1 folic acid. The detection limits for 6-thioguanine and folic acid were 0.0085 μmol L −1 and 1.1 μmol L −1, respectively. The RSD% for 10 replicates determination of 0.70 and 11.0 μmol L −1 of 6-thioguanine were 1.3% and 1.1%, respectively, whereas for 15.0 and 30.0 μmol L −1 folic acid, they were 0.9% and 1.1%, respectively. The modified electrode showed good sensitivity, selectivity, and stability. It was successfully applied for the determination of both 6-thioguanine and folic acid in real samples.

Coordination polymers containing ferrocene backbone. Synthesis, structure and electrochemistry

The reaction of 1,1'-ferrocenedicarboxylic acid (LH(2)) with bis(triphenyltin) oxide afforded a molecular heterobimetallic compound [(Ph(3)Sn)(2)L]. In the latter the two carboxylate units of [L](2-) are involved in an anisobidentate chelating coordination mode to two triphenyl tin units. The reaction of LH(2) with trimethyltin hydroxide or bis(tri-n-butyltin) oxide afforded 2D-coordination polymers [(Me(3)Sn)(2)L](n) and [(n-Bu(3)Sn)(2)L](n) which are formed as a result of anisobidentate bridging coordination action of the two carboxylate units of [L](2-). Interestingly the 2D-coordination polymers contain 24-membered macrocycles each of which is comprised of four trialkyl tin units. The coordination unsaturation of [(Ph(3)Sn)(2)L] can be utilized to form coordination polymers. Accordingly the reaction of LH(2) with bis(triphenyltin) oxide in the presence of ditopic nitrogen ligands such as 4,4'-bipyridine, 4,4'-trimethylenebipyridine or 4,4'-vinylenebipyridine afforded one-dimensional coordination polymers which contain in their backbone three distinct structural components viz., two triorganotin units, a ferrocenyl unit and a bridging nitrogen ligand unit. The coordination polymers, however, do not retain their structural integrity in solution and fall apart to their monomeric units. Electrochemical studies on these hybrid orgaonotin/ferrocene systems reveal that most of them exhibit a single quasi-reversible oxidation peak.

Heterogeneous electron transfer kinetics and electrocatalytic behaviour of mixed self-assembled ferrocenes and SWCNT layers

The electron transfer dynamics and electrocatalytic behaviour of ferrocene-terminated self-assembled monolayers (SAMs), co-adsorbed with single-walled carbon nanotubes (SWCNTs) on a gold electrode, have been interrogated for the first time. Ferrocene monocarboxylic acid (FMCA) or ferrocene dicarboxylic acid (FDCA) was covalently attached to the cysteamine (Cys) monolayer to form Au-Cys-FMCA and Au-Cys-FDCA, respectively. The same covalent attachment strategy was used to form the mixed SWCNTs and ferrocene-terminated layers (i.e. Au-Cys-SWCNT/FMCA and Au-Cys-SWCNT/FDCA). Using cyclic voltammetry and electrochemical impedance spectroscopy, the impact of neighbouring SWCNTs on the electron transfer dynamics of the ferrocene molecular assemblies in an acidic medium (0.5 M H(2)SO(4)) and in a solution of an outer-sphere redox probe ([Fe(CN)(6)](4-)/[Fe(CN)(6)](3-)) was explored. The electron transfer rate constants in both media essentially decreased as Au-Cys-FMCA > Au-Cys-SWCNT/FDCA > Au-Cys-FDCA > Au-Cys-SWCNT/FMCA. This trend has been interpreted in terms of several factors such as the locations of the ferrocene species in a range of environments with a range of potentials, the proximity/interactions of the ferrocenes with one another, and electrostatic interaction or repulsion existing between the negatively-charged redox probe and the modified electrodes. The thiocyanate ion (SCN(-)) was used as a model analyte to examine the influence of the neighbouring SWCNTs on the electrocatalytic ability of the ferrocene assemblies. The Au-Cys-SWCNT/FDCA showed the best catalytic activity (in terms of onset potential and catalytic peak current height) for the oxidation of SCN(-), possibly due to the repulsive interactions between the negatively charged SCN(-) and high number of surface -COOH species at the SWCNT/FDCA. This study has provided some useful insights as to how CNTs co-assembled with ferrocene-terminated thiols could impact on the electron transfer kinetics as well as the electrocatalytic detection of the self-assembled ferrocene layers.

Electronic Transport Properties of 1,1′-Ferrocene Dicarboxylic Acid Linked to Al(111) Electrodes

The electronic transport properties of the 1,1'-ferrocene dicarboxylic acid sandwiched between Al(111) electrodes are studied using first-principles methods. The transmission spectra and the current-voltage characteristics are computed for various two-terminal device models and their relation with the electronic structure of the molecule is thoroughly discussed. The current-voltage characteristics are asymmetric, spin-independent, and vary with the anchoring structure of the molecule to the electrodes. A fine-tuning of the molecular conductance can be easily achieved by applying a gate potential, which is included in our simulations. Interestingly, a spin-polarized current can emerge as a consequence of the gate potential with the relative contribution of the two spin channels varying with the bias.

New penta-nuclear and hepta-nuclear iron(II, III) complexes with ferrocenedicarboxylic acid

The reaction of [Fe 3EuO 2(O 2CCCl 3) 8(H 2O)(THF) 3] or [Fe 2CaO(O 2CCCl 3) 6(THF) 4] and [Fe 3O(O 2CCMe 3) 6(H 2O) 3]NO 3 with 1,1′-ferrocenedicarboxylic acid (fcdcH 2) yielded penta- and hepta-nuclear [Fe 4O 2(O 2CCCl 3) 6(fcdc)(THF) 2(H 2O) 2] and [Fe 6O 2(OH) 2(O 2CCMe 3) 10(fcdc)(H 2O) 2], respectively, which are the first X-ray structurally characterized clusters comprising Fe(III) and the ferrocenedicarboxylic organometallic ligand. Variable-temperature solid-state magnetic susceptibility measurements in the temperature range 1.8–300 K were carried out, and for both complexes a predominantly antiferromagnetic exchange interaction between the metal centres was observed. Mössbauer investigations show the presence of different environments for the Fe(III) atoms and confirm that no electron-transfer from Fe(II) of the ferrocene unit to Fe(III) of the central core occurs.

Redox‐ and pH‐Controlled Mechanized Nanoparticles

AbstractA new class of mechanized silica nanoparticles, which exploits the stability of the inclusion complexes formed between ferrocenedicarboxylic acid and both cucurbit[7]uril (CB7) and β‐cyclodextrin (β‐CD), are described. Mesoporous silica nanoparticles, capable of storing a payload of small molecules and releasing it following particular activation processes, have been designed and decorated with ferrocenecarboxylic acid stalks. The storage and release of the payload is controlled by the host–guest interaction between the ferrocene moiety (guest) and the ring moiety (CB7 or β‐CD). Ferrocene‐based Mechanized NanoParticles (FMNPs) were efficiently prepared, loaded with Rhodamine dye, and then tested under different activation procedures. The systems operated successfully under redox control (oxidation of ferrocenedicarboxylic acid) in the presence of β‐CD and under pH control (deprotonation of ferrocenedicarboxylic acid pH > 4) in the presence of CB7.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Electrocatalytic Determination of Ampicillin Using Carbon-Paste Electrode Modified with Ferrocendicarboxylic Acid

A carbon-paste electrode spiked with ferrocenedicarboxylic acid (FDCMCPE) was constructed by incorporation of ferrocenedicarboxylic acid in a graphite powder–paraffin oil matrix. It has been shown by direct current cyclic voltammetry and double-step chronoamperometry that this electrode can catalyze the oxidation of ampicillin (AMPC) in aqueous buffered solution. It has been found that under the optimum condition (pH 10.0) in cyclic voltammetry, the oxidation of AMPC occurred at a potential of about 480 mV on the surface of the modified carbon-paste electrode. The kinetic parameters such as electron-transfer coefficient, α, and rate constant for the chemical reaction between AMPC and redox sites in FDCMCPE were also determined using electrochemical approaches. Under the optimized conditions, the electrocatalytic oxidation peak current of AMPC showed two linear dynamic ranges with a detection limit of 0.67 µmol L−1 AMPC. The linear calibration was in the range of 2.34–30 µmol L−1 and 40–700 µmol L−1 AMPC using the differential pulse voltammetric method. Finally, this method was also examined as a selective, simple, and precise electrochemical sensor for the determination of AMPC in real samples such as drugs and urine.

Electron Transfer through a Self-Assembled Monolayer of a Double-Helix Peptide with Linking the Terminals by Ferrocene

A unique molecular structure, a double-helix peptide, was self-assembled on gold, and the electron transfer through the monolayer was studied. The double-helix peptide consists of two 9mer 3(10)-helical peptide chains having a disulfide group at each N terminal and being linked by a ferrocene dicarboxylic acid between the C terminals. Each helical peptide chain has three naphthyl groups in a linear arrangement along the helix. The monolayer properties and the electron transfer from the ferrocene unit to gold were studied with reference peptides with a similar double helix but without naphthyl groups, a single helix with a dicarboxylic ferrocene unit, and a single helix with a monocarboxylic ferrocene unit. It was demonstrated that the naphthyl groups on the side chains had no effect on electron transfer, and the electron-transfer rate in the double-helix monolayer was not promoted, despite the two electron pathways in the molecule. We propose that in the double-helix monolayer, molecular motions are suppressed, possibly by its rigid structure tethered by the two linkers on gold to cancel out acceleration effects of the 2-fold electron pathways and the ferrocene substitution number. The factors that affect the electron-transfer reaction across the helical peptide SAMs are discussed in depth.

Fast and sensitive determination of captopril by voltammetric method using ferrocenedicarboxylic acid modified carbon paste electrode

A ferrocenedicarboxylic acid modified carbon paste electrode was constructed and used as a fast and sensitive tool for the determination of captopril at trace level. It has been shown by direct current cyclic voltammetry and double step chronoamperometry that ferrocenedicarboxylic acid can catalyze the oxidation of captopril in aqueous buffer solution and produces a sharp oxidation peak current at about +0.49 vs. Ag/AgCl reference electrode. The square wave voltammetric peak currents of the electrode increased linearly with the corresponding captopril concentration in the range of 3.0 × 10−7–1.4 × 10−4M with a detection limit of 9.1 × 10−8 M. The influence of pH and potential interfering substances on the determination of captopril were studied. Electrochemical impedance spectroscopy was used to study the charge transfer properties at the electrode–solution interface. Finally, the sensor was examined as a selective, simple, and precise new electrochemical sensor for the determination of captopril in real samples, such as drug and urine, with satisfactory results.

Synthesis and characterization of new ferrocene peptide conjugates

Three classes of diamine linked ferrocene (Fc)-conjugates were prepared and their properties were investigates in solution and the solid state: (a) acyclic diamine-linked 1,n'-Fc conjugates, (b) acyclic diamine-linked 1,n'-Fc peptide conjugates, and (c) cyclic 1,n'-Fc-peptide diamine conjugates. In all cases, the synthetic procedure started from 1,1'-ferrocenecarboxylic acid methyl ester or 1,1'-ferrocene dicarboxylic acid or their amino acid conjugates followed by coupling with diaminoalkanes. The resulting conjugates exhibit H-bonding as is evident by temperature and, in some cases, concentration-dependent NMR shifts and in the solid-state structure of one of the conjugates. Our studies show that the structural properties of Fc-diamine-linked systems are different from those of the related cystamine conjugates, presumably due to the enhanced flexibility of the conjugates.

Reaction chemistry of 1,1′-ferrocene dicarboxylate towards M(ii) salts (M = Co, Ni, Cu): solid-state structure and electrochemical, electronic and magnetic properties of bi- and tetrametallic complexes and coordination polymers

The synthesis and characterisation of a series of novel complexes of type [((tmeda)M-OC(O)-fc-(micro-CO(2)))(2)(micro-H(2)O)] (M = Co, ; M = Ni, ), zwitter-ionic [((pmdta)(H(2)O)Cu(+)-OC(O)-fc-CO(2)(-))(CH(3)OH)] (), and coordination polymer [(tmeda)Cu((OC(O))(2)fc)](n) () (fc = ferrocene-1,1'-diyl, (eta(5)-C(5)H(4))(2)Fe; tmeda = N,N,N',N'-tetramethylethylenediamine; pmdta = 1,1,4,7,7-N,N,N',N'',N''-pentamethyldiethylenetriamine) composed of ferrocene dicarboxylates and [(tmeda)/(pmdta)M](2+) entities is reported. These complexes could be prepared from [M(NO(3))(2)(tmeda)] (M = Co, ; M = Ni, ; M = Cu, ) and [Cu(NO(3))(2)(pmdta)] (), respectively, with stoichiometric amounts of 1,1'-ferrocene dicarboxylic acid () in presence of [n-Bu(4)N]OH-H(2)O. The molecular structures of , , , and in the solid state have been determined by single-crystal X-ray structure analysis. Electrochemical and UV-vis-NIR spectroscopic studies of these complexes are discussed in terms of electronic communication between the redox-active transition metals. In addition, the magnetic properties of and have been studied by susceptibility measurements vs. temperature. In complex , the two cobalt(ii) ions are antiferromagnetically coupled, while in the Ni-Ni coupling is ferromagnetic with J approximately +2.2(1) cm(-1).