Ferrocene Functionalized Research Articles

Conductive Mediators in Oxidation Based on Ferrocene Functionalized Phosphonium Ionic Liquids

Herein, the synthesis of ferrocene-containing salts is presented. Acylation of ferrocene (Fc) according to the Friedel-Crafts method led to ω-bromoacyl ferrocenes. The ω-bromoacyl ferrocenes were subsequently introduced to quaternization reaction with tri-tert-butyl phosphine, which resulted in phosphonium salts. Obtained phosphonium salts were characterized by physical methods. The electrochemical properties of phosphonium salts were studied by cyclic voltammetry (CV). It was found that the replacement of n-butyl fragments at the phosphorus atom by tert-butyl leads to a more anodic potential shift. In contrast to isolobal structures Fc-C(O)(CH2)nP+(n-Bu)3X- and Fc-(CH2)n+1P+(n-Bu)3X-, the CV curves of Fc-C(O)(CH2)nP+(t-Bu)3X- and Fc-(CH2)n+1P+(t-Bu)3X- did not show a large discrepancy between forward and reverse currents. The transformation of the C=O groups to CH2 fragments had a significant effect on the electrochemical properties of ferrocene salts, the oxidation potential of which is close to that of pure ferrocene.

Impact of Coordination Mode and Ferrocene Functionalization on the Anticancer Activity of N-Heterocyclic Carbene Half-Sandwich Complexes.

The substitution of phenyl rings in established drugs with ferrocenyl moieties has been reported to yield compounds with improved biological activity and alternative modes of action, often involving the formation of reactive oxygen species (ROS). Translating this concept to N-heterocyclic carbene (NHC) complexes, we report here organometallics with a piano-stool structure that feature di- or tridentate ligand systems. The ligands impacted the cytotoxic activity of the NHC complexes, but the coordination modes seemed to have a limited influence, which may be related to the propensity of forming the same species in solution. In general, the stability of the complexes in an aqueous environment and their reactivity to selected biomolecules were largely dominated by the nature of the metal center. While the complexes promoted the formation of ROS, the levels did not correlate with their cytotoxic activity. However, the introduction of ferrocenyl moieties had a significant impact on the antiproliferative potency of the complexes and, in particular, some of the ferrocenyl-functionalized compounds yielded IC50 values in the low μM range.

Ferrocene Functionalized Upconversion Nanoparticle Nanosystem with Efficient Near-Infrared-Light-Promoted Fenton-Like Reaction for Tumor Growth Suppression.

By taking advantage of the efficient Förster resonance energy transfer (FRET) between near-infrared (NIR)-responsive lanthanide-doped upconversion nanoparticles (UCNPs) and Fenton reagent ferrocenyl compounds (Fc), a series of Fc-UCNPs was designed by functionalizing NaYF4:Yb,Tm nanoparticles with Fc1-Fc5 via surface-coordination chemistry. Fc-UCNP-Lipo nanosystems were then constructed by encapsulating Fc-UCNP inside liposomes for efficient delivery. Fc-UCNP can effectively release ·OH via a NIR-promoted Fenton-like reaction. In vitro and in vivo studies of Fc1-UCNP-Lipo confirmed the preferential accumulation in a tumor site followed by an enhanced uptake of cancer cells. After cellular internalization, the released Fc1-UCNP can effectively promote ·OH generation for tumor growth suppression. Such a Fc1-UCNP-Lipo nanosystem exhibits advantages such as easy fabrication, low drug dosage, and no ferrous ion release.

Increasing the Sensitivity of Electrochemical DNA Detection by a Micropillar-Structured Biosensing Surface.

The available active surface area and the density of probes immobilized on this surface are responsible for achieving high specificity and sensitivity in electrochemical biosensors that detect biologically relevant molecules, including DNA. Here, we report the design of gold-coated, silicon micropillar-structured electrodes functionalized with modified poly-l-lysine (PLL) as an adhesion layer to concomitantly assess the increase in sensitivity with the increase of the electrochemical area and control over the probe density. By systematically reducing the center-to-center distance between the pillars (pitch), denser micropillar arrays were formed at the electrode, resulting in a larger sensing area. Azido-modified peptide nucleic acid (PNA) probes were click-reacted onto the electrode interface, exploiting PLL with appended oligo(ethylene glycol) (OEG) and dibenzocyclooctyne (DBCO) moieties (PLL-OEG-DBCO) for antifouling and probe binding properties, respectively. The selective electrochemical sandwich assay formation, composed of consecutive hybridization steps of the target complementary DNA (cDNA) and reporter DNA modified with the electroactive ferrocene functionality (rDNA-Fc), was monitored by quartz crystal microbalance. The DNA detection performance of micropillared electrodes with different pitches was evaluated by quantifying the cyclic voltammetric response of the surface-confined rDNA-Fc. By decrease of the pitch of the pillar array, the area of the electrode was enhanced by up to a factor 10.6. A comparison of the electrochemical data with the geometrical area of the pillared electrodes confirmed the validity of the increased sensitivity of the DNA detection by the design of the micropillar array.

A Facile Synthesis of Ferrocene Functionalized Graphene Oxide Nanocomposite for Electrochemical Sensing of Lead

Ferrocene, an organometallic compound has the potential to undergo reversible oxidation even at low potential which makes it suitable for electrochemical sensor applications. The potential of graphene oxide has been widely exploited in electrochemistry, since they serve as an excellent platform for electrochemical molecules and increase the electrochemical properties. The potential of Graphene oxide-ferrocene (GO-Fc) nanocomposites has not been realized much in fabrication of electrochemical sensors. Hence, the electrochemical properties of the pure Ferrocene and GO-Fc nanocomposites were investigated. Graphene oxide (GO) was synthesised by modified Hummer’s method and was conjugated with ferrocene at different weight ratio after thermal treatment. The as-prepared pure GO and GO-Fc nanocomposites were characterized by various analytical methods. Monoclinic phase of Ferrocene was observed in XRD. Surface functionalization of Ferrocene on GO was imaged by TEM. Ferrocene particles were observed to be rod shaped and functionalized on surface of GO in TEM images. The composite formation was validated by FTIR and Raman by the presence of aromatic ring and ferrocene bands respectively. AAS results showed 87% ferrocene loading capacity in GO-Fc composite 2 (GF2) which decreased to 77% in GO-Fc composite 5 (GF5). Based on the CV curves, and ferrocene loaded on GO, GO-Fc composite 4 (GF4) was chosen for evaluating the lead sensing property. The sensing studies showed a detection limit of 0.168 µg/l with significant sensitivity up to 250 µg/l. The results indicate that GO-Fc nanocomposites can be potentially used for sensing lead in environmental samples.

A Click‐Generated Triethoxysilane Tethered Ferrocene‐Chalcone‐Triazole Triad for Selective and Colorimetric Detection of Cu2+ Ions

AbstractThis article describes an efficient synthetic approach to design ferrocene tailed chalcone appended triazole encapped organosilanes (7‐12) from acetylinic ferrocene precursors (1‐6). The synthesized compounds were well characterized by general spectroscopic techniques. The framed ligands were then evaluated for their ion sensing properties and were found to display significant perturbation in their absorption and emission behaviour upon addition of Cu2+ ions. Their sensing ability is highly reversible on addition of ethylenediaminetetraacetic acid (EDTA) and hence can be employed as potential Cu(II) sensing materials. In addition, the presence of ferrocene functionality overtures an electro active unit generating a multiple signalling sensor that also offers naked eye detection of Cu(II) ions with analytical detection limit of as low as 10 μM. Above all, the designed chemosensor exhibits tolerance against other metal ions which enables the Cu2+ ion detection even in a complex matrix. Complexation behaviour of one of the silanes, FCTS 12 was also deliberated by computational analysis following DFT approach.

Induction of Cytotoxicity in Pyridine Analogues of the Anti-metastatic Ru(III) Complex NAMI-A by Ferrocene Functionalization.

A series of novel ferrocene (Fc) functionalized Ru(III) complexes was synthesized and characterized. These compounds are derivatives of the anti-metastatic Ru(III) complex imidazolium [trans-RuCl4(1H-imidazole) (DMSO-S)] (NAMI-A) and are derived from its pyridine analogue (NAMI-Pyr), with direct coupling of Fc to pyridine at the 4 or 3 positions, or at the 4 position via a two-carbon linker, which is either unsaturated (vinyl) or saturated (ethyl). Electron paramagnetic resonance (EPR) and UV-vis spectroscopic studies of the ligand exchange processes of the compounds in phosphate buffered saline (PBS) report similar solution behavior to NAMI-Pyr. However, the complex with Fc substitution at the 3 position of the coordinated pyridine shows greater solution stability, through resistance to the formation of oligomeric species. Further EPR studies of the complexes with human serum albumin (hsA) indicate that the Fc groups enhance noncoordinate interactions with the protein and help to inhibit the formation of protein-coordinated species, suggesting the potential for enhanced bioavailability. Cyclic voltammetry measurements demonstrate that the Fc groups modestly reduce the reduction potential of the Ru(III) center as compared to NAMI-Pyr, while the reduction potentials of the Fc moieties of the four compounds vary by 217 mV, with the longer linkers giving significantly lower values of E1/2. EPR spectra of the compounds with 2-carbon linkers show the formation of a high-spin Fe(III) species (S = 5/2) in PBS with a distinctive signal at g = 4.3, demonstrating oxidation of the Fe(II) ferrocene center and likely reflecting degradation products. Density functional theory calculations and paramagnetic (1)H NMR describe delocalization of spin density onto the ligands and indicate that the vinyl linker could be a potential pathway for electron transfer between the Ru and Fe centers. In the case of the ethyl linker, electron transfer is suggested to occur via an indirect mechanism enabled by the greater flexibility of the ligand. In vitro assays with the SW480 cell line reveal cytotoxicity induced by the ruthenium ferrocenylpyridine complexes that is at least an order of magnitude higher than the unfunctionalized complex, NAMI-Pyr. Furthermore, migration studies with LNCaP cells reveal that Fc functionalization does not reduce the ability of the compounds to inhibit cell motility. Overall, these studies demonstrate that NAMI-A-type compounds can be functionalized with redox-active ligands to produce both cytotoxic and anti-metastatic activity.

Development of a redox polymer based on poly(2-hydroxyethyl methacrylate) for disposable amperometric sensors

Membranes based on poly(2-hydroxyethyl methacrylate), chemically modified with ferrocene functionalities, are proposed as novel coatings for the development of disposable amperometric sensors. They are mass-produced on an inert support through an UV photo-induced polymerization, forming self-standing films that can be transferred on an electrode surface. Thanks to the characteristic of the functionalized methacrylate matrix to rapidly and reversibly swell by incorporation of large amounts of water, the ferrocene moieties are in intimate contact with the electrolytic solution. They can activate effective electrocatalytic processes that can be exploited in the field of amperometric sensing. The performance of the methacrylate coating with respect to the determination of hydroquinone benchmark analyte has been tested both in a static solution and in a flux cell.

Rotaxane and Catenane Host Structures for Sensing Charged Guest Species

CONSPECTUS: The promise of mechanically interlocked architectures, such as rotaxanes and catenanes, as prototypical molecular switches and shuttles for nanotechnological applications, has stimulated an ever increasing interest in their synthesis and function. The elaborate host cavities of interlocked structures, however, can also offer a novel approach toward molecular recognition: this Account describes the use of rotaxane and catenane host systems for binding charged guest species, and for providing sensing capability through an integrated optical or electrochemical reporter group. Particular attention is drawn to the exploitation of the unusual dynamic properties of interlocked molecules, such as guest-induced shuttling or conformational switching, as a sophisticated means of achieving a selective and functional sensor response. We initially survey interlocked host systems capable of sensing cationic guests, before focusing on our accomplishments in synthesizing rotaxanes and catenanes designed for the more challenging task of selective anion sensing. In our group, we have developed the use of discrete anionic templation to prepare mechanically interlocked structures for anion recognition applications. Removal of the anion template reveals an interlocked host system, possessing a unique three-dimensional geometrically restrained binding cavity formed between the interlocked components, which exhibits impressive selectivity toward complementary anionic guest species. By incorporating reporter groups within such systems, we have developed both electrochemical and optical anion sensors which can achieve highly selective sensing of anionic guests. Transition metals, lanthanides, and organic fluorophores integrated within the mechanically bonded structural framework of the receptor are perturbed by the binding of the guest, with a concomitant change in the emission profile. We have also exploited the unique dynamics of interlocked hosts by demonstrating that an anion-induced conformational change can be used as a means of signal transduction. Electrochemical sensing has been realized by integration of the redox-active ferrocene functionality within a range of rotaxane and catenanes; binding of an anion perturbs the metallocene, leading to a cathodic shift in the ferrocene/ferrocenium redox couple. In order to obtain practical sensors for target charged guest species, confinement of receptors at a surface is necessary in order to develop robust, reuseable devices. Surface confinement also offers advantages over solution based receptors, including amplification of signal, enhanced guest binding thermodynamics and the negation of solubility problems. We have fabricated anion-templated rotaxanes and catenanes on gold electrode surfaces and demonstrated that the resulting mechanically bonded self-assembled monolayers are electrochemically responsive to the binding of anions, a crucial first step toward the advancement of sophisticated, highly selective, anion sensory devices. Rotaxane and catenane host molecules may be engineered to offer a superior level of molecular recognition, and the incorporation of optical or electrochemical reporter groups within these interlocked frameworks can allow for guest sensing. Advances in synthetic templation strategies has facilitated the synthesis of interlocked architectures and widened their interest as prototype molecular machines. However, their unique host-guest properties are only now beginning to be exploited as a sophisticated approach to chemical sensing. The development of functional host-guest sensory systems such as these is of great interest to the interdisciplinary field of supramolecular chemistry.

Preparation of Ferrocene Functionalized Multiwall Carbon Nanotube Nanocomposites and its Electrochemical Behavior

Ferrocenecarboxaldehyde (FcCHO) was covalently bound onto the multi-wall carbon nanotubes functionalized with amino groups (AMWNTs) to achieve Fc-AMWNTs conjugate. The cyclic voltammetry were used to characterize the nanocomposites. Here, Fc-AMWNTs were applied to construct glucose biosensors with IO4--oxidized glucose oxidase (IO4--oxidized GOx) through the covalent assembly method without any cross-linker. The presence of both ferrocene as mediator of electron transfer and MWNTs as conductor enhanced greatly the electrocatalytic response toward the glucose. Furthermore, our enzyme electrodes also showed remarkable stability due to the covalent interaction between the Fc-AMWNTs and the GOx.

Ferrocene incorporated PAMAM dendrons: synthesis, characterization, and anti-cancer activity against AGS cell line

Novel series of asymmetric Poly(amidoamine) (PAMAM) dendrons containing a single ferrocene unit located as the focal point has been prepared. First, second, and third generation ferrocene-PAMAM dendrons with branched amine periphery and focal ferrocene functionality were synthesized via divergent pathways. The synthesized dendrons were characterized by FT-IR and NMR spectroscopy. Real-time cell analysis, cell viability, and anti-cancer activity of ferrocene-PAMAM dendrons were evaluated in AGS cells. While cell viability decreased, anti-cancer activity increased gradually in a dose-dependent manner in one, two, and three generations.

Novel cross-linkers for PDMS networks for controlled and well distributed grafting of functionalities by click chemistry

An azide-containing, trifunctional vinyl cross-linker for silicone networks has been synthesized. The cross-linker has through Cu(I) catalyzed 1,3-cycloaddition been reacted with six different alkyne-containing chemical groups which each possess a particular functionality. The functional cross-linkers have been utilized to prepare novel polydimethylsiloxane (PDMS) networks. All functional cross-linkers were successfully incorporated into the networks and were demonstrated to be well distributed within the PDMS films. This was substantiated by fluorescence microscopy of a film prepared with the 4-methyl-umbelliferone containing cross-linker. TGA showed that a ferrocene functionality increased the thermal degradation temperature of PDMS. It was furthermore shown that the incorporation of only 0.25 wt% of the push–pull dipole, ethynyl-4-nitrobenzene, increased the dielectric permittivity of PDMS by 35%. The contact angle of PDMS films was increased from 108° to 116° by the introduction of a small poly(pentafluorostyrene) chain. Finally, 17α-ethynyl-1,3,5(10)-estratriene-3,17β-diol and 1-ethynyl-3,5-bis(trifluoromethyl)benzene were incorporated as examples of other functional groups.

The Syntheses and Electrochemical Studies of a Ferrocene Substituted Diiminopyridine Ligand and Its P, S, Se, and Te Complexes

A new reversible, redox active diiminopyridine ligand (1Fc) containing pendant ferrocene functionalities was isolated and fully characterized. The reaction of 1Fc with chalcogen pseudohalides of sulfur, selenium, and tellurium yielded the respective N,N',N″-chelated chalcogen dications. Phosphorus chemistry proceeded in a related manner but, in this case, by the direct addition of 1Fc with PI(3) to yield the N,N',N″-chelated P(I) cation. These species represent the first synthesized main group complexes involving a redox active diiminopyridine ligand containing pendant ferrocenes. Electrochemical studies of the free ligand shows a reversible two-electron process. The chelated phosphorus cation, however, displayed three events, the first being a quasi-reversible two-electron process, involving the oxidation at the P(I) center, resulting in a P(III) cation. The subsequent reversible one- and two-electron processes arise from the ligand framework and pendant ferrocenes, respectively.

Pulsed chronopotentiometric membrane electrodes based on plasticized poly(vinyl chloride) with covalently bound ferrocene functionalities as solid contact transducer

Ion-selective membrane materials based on poly(vinyl chloride) (PVC)-containing covalently attached redox-active ferrocene (Fc) groups are characterized here as all-solid-state pulsed voltammetric ion sensors. The redox capacity of the membrane increases 7-fold with a doubling of the Fc content and 3-fold with the addition of 10 wt % of the lipophilic electrolyte ETH 500, tetradodecylammonium tetrakis(4-chlorophenyl)borate. This salt improves the ionic conductivity of the membrane and appears to make the Fc groups electrochemically more accessible. A too high content of the two, on the other hand, was found to cause undesired sensitivity to redox-active species present in the sample solution. Dilution of the membrane with a plasticizer eliminated this redox sensitivity while preserving its high redox capacity. A practical application of the designed electrodes in electrochemical analysis was demonstrated with a multi-pulse protocol that includes a current-controlled ion uptake pulse, followed by an open-circuit potential (OCP) measurement and a regeneration pulse. Potentiometric calibration curves obtained with this protocol exhibited a linear response with near-Nernstian slopes for acetate, nitrate, chloride, and perchlorate ions with the selectivity expected for an ion-exchanging membrane.

ChemInform Abstract: Metal‐Catalyzed Cross‐Coupling Reactions for Ferrocene Functionalization: Recent Applications in Synthesis, Material Science and Asymmetric Catalysis

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Cerium ammonium nitrate: an efficient catalyst for carbon–carbon bond formation from ferrocenyl alcohol substrate

The substitution reaction of ferrocenyl alcohol with various nucleophiles catalyzed by cerium ammonium nitrate (CAN) was investigated. This CAN-mediated direct carbon–carbon bond formation provides the corresponding products in moderate to high yields with relatively lower catalyst loading (5 mol %) at room temperature. It demonstrated a convenient synthetic protocol for the ferrocene functionalities.

Metal-Catalyzed Cross-Coupling Reactions for Ferrocene Functionalization: Recent Applications in Synthesis, Material Science and Asymmetric Catalysis

Recent examples on the functionalization of the ferrocene core by means of cross-coupling reactions are reported in this review. Several methods are discussed including Negishi, Suzuki and Stille couplings for ferrocene-aryl bond formation and Sonogashira reaction for ferrocene-alkyne coupling. The properties in material science and asymmetric catalysis of the prepared ferrocenyl compounds are briefly discussed.

Self-assembly of a heterometallic molecular triangle using an ambidentate ligand and self-selection for a single linkage isomer

Self-assembly and self-selection of a single linkage isomer of a mixed-metal molecular triangle with ferrocene functionality have been achieved using an ambidentate ligand, and the product was characterized by multinuclear NMR spectroscopy and X-ray single crystal structure determination.

Modified Electrodes Prepared from Ferrocene Functionalized Silicate Xerogels: Analysis of the Electrochemical Response in Isotropic and Fractal Structural Systems

New xerogels functionalized by ferrocenes as redox probes have been prepared using various types of catalysis. The analysis of the electrochemical response in the case of modified electrodes allows us to get an insight into the gel nanostructure which has been found to be isotropic in the case of acidic catalysis, and fractal in the case of fluoride catalysis, provided that the amount of functionalized silanes is not too high. Indeed the results of electrochemical measurement prove that the fractality of functionalized hybrid silica is general in the case of basic catalysis, except in the case of very high functional moieties loading, where the electrode become essentially organic and isotropic. On the other hand, in the case of acidic catalysis, whatever the amount of organic material, the hybrid gel remains isotropic, and a classical electron pseudo-diffusive behaviour is observed. The diffusion coefficient values extracted from the current-time slopes do not vary monotonically with the amount of redox probe in the case of fractal xerogel structures, which is indicative that not all the functional moieties are electroactive in that case.

Chemical modification of silicon surfaces with ferrocene functionalities

The functionalisation of macro- and meso-porous silicon surfaces with ferrocene groups using organometallic approaches has been performed via an organic (3-halogenpropyl) siloxy spacer or direct bonding. FTIR spectroscopy has been used for characterisation of the silicon surface at each step of chemical processes.