Search

Selective two‐electron reduction of dioxygen (O2) to hydrogen peroxide (H2O2) has been achieved by two saddle‐distorted N,N'‐dimethylated porphyrin isomers, an N21,N'22‐dimethylated porphyrin (anti‐Me2P) and an N21,N'23‐dimethylated porphyrin (syn‐Me2P) as catalysts and ferrocene derivatives as electron donors in the presence of protic acids in acetonitrile. The higher catalytic performance in an oxygen reduction reaction (ORR) was achieved by anti‐Me2P with higher turnover number (TON=250 for 30 min) than that by syn‐Me2P (TON=218 for 60 min). The reactive intermediates in the catalytic ORR were confirmed to be the corresponding isophlorins (anti‐Me2Iph or syn‐Me2Iph) by spectroscopic measurements. The rate‐determining step in the catalytic ORRs was concluded to be proton‐coupled electron‐transfer reduction of O2 with isophlorins based on kinetic analysis. The ORR rate by anti‐Me2Iph was accelerated by external protons, judging from the dependence of the observed initial rates on acid concentrations. In contrast, no acceleration of the ORR rate with syn‐Me2Iph by external protons was observed. The different mechanisms in the O2 reduction by the two isomers should be derived from that of the arrangement of hydrogen bonding of a O2 with inner NH protons of the isophlorins. [ABSTRACT FROM AUTHOR]

The title ferrocene derivative, [Fe(C5H5)2(C8NO2)], including an alkyne bonded to a para-nitrophenyl substituent, which was synthesized from a copper-free Sonogashira cross-coupling reaction between ethynylferrocene and 4-bromo-1- nitrobenzene, crystallizes in the P21/n space group. In the ferrocene unit, the pentadienyl (Cps) rings are in an eclipsed conformation. The angle of rotation between the substituted cyclopentadienyl ring and the p-nitrophenyl group is 6.19 (10), yielding a quasi-linear extension of the ferrocenyl substitution. Important intermolecular interactions arise from π–π stacking between the Cp rings and the p-nitrophenyl, from corners of the Cp rings that are perpendicularly aligned, and between the O atoms from the nitro substituent and carbons at the corners of the Cp rings, propagating along all three crystallographic axes. [ABSTRACT FROM AUTHOR]

Novel ferrocene conjugates of tricyclic quinazoline derivatives are prepared by condensation of active C‐6 methylene groups of mackinazolinones with ferrocenecarbaldehyde. Following this route the conjugated parent alkaloid as well as derivatives with nitro, amino, and alkanoylamino groups at C‐2 were attached at the ferrocene moiety, thereby significantly extending the delocalized π system. In addition, the parent compound was subjected to the reaction with ferrocene‐1,1'‐dicarbaldehyde, giving rise to the symmetrical and unsymmetrical double condensation products – 1,1'‐disubstituted ferrocene derivatives, which bear two alkaloid substituents. Some of the compounds obtained were subjected to X‐ray crystallographic analyses. The influence of the substituents at C‐2 through the extended conjugated π system on the iron atom is reflected by results of cyclovoltammetric measurements. [ABSTRACT FROM AUTHOR]

The kinetics of redox isomerization of ferrocenylcarbenium ions obtained via protonation of ferrocene derivatives with perchloric acid in dioxane has been studied by means of electron absorption spectroscopy method from accumulation of ferrocenium cations. It has been shown that the dependences of the rate of ferrocenium cations accumulation on the components concentration is extremal in certain cases and is determined by the nature of metal complex and the initial ratio of the metal complex and acid. Stabilization of carbocations via their solvation with acetonitrile, DMF, and DMSO as well as via coordination with the starting compound leads to partial or complete loss of their ability to redox isomerization. Schemes of the metal complexes protonation and results of their kinetic analysis confirming the obtained concentration dependencies are given. [ABSTRACT FROM AUTHOR]

Cervical cancer is one of the most common types of cancer in women, with approximately 500,000 new cases and 250,000 deaths every year. Radiotherapy combined with chemotherapy represents the treatment of choice for advanced cervical carcinomas. The role of the chemotherapy is to increase the sensitivity of the cancer cells to irradiation. Cisplatin, the most commonly used drug for this purpose, has its limitations. Thus, we used a family of ferrocene derivatives (in addition, one new species was prepared using standard Schlenk techniques) and studied their effects on cervical cancer cells alone and in combination with irradiation. We applied colorimetric assay to determine the cytotoxicity of the compounds; flow cytometry to analyze the production of reactive oxygen species (ROS), cell cycle, and mitochondrial membrane potential (MMP); immunochemistry to study protein expression; and colony forming assay to evaluate changes in radiosensitivity. Treatment with ferrocenes exhibited significant cytotoxicity against cervical cancer cells, associated with increasing ROS production and MMP changes, suggesting the induction of apoptosis. The combined activity of ferrocenes and ionizing radiation highlighted ferrocenes as potential radiosensitizing drugs, while their higher single-agent toxicity in comparison with routinely used cisplatin could also be promising. Our results demonstrate antitumor activity of several tested ferrocenes both alone and in combination with radiotherapy. [ABSTRACT FROM AUTHOR]

An efficient synthesis of ferrocene derivatives via rhodium(III)‐catalyzed direct C−H alkylation with diazo compounds under weakly coordinating group has been presented. This protocol provides an approach towards access to various ferrocene derivatives using carboxamides, giving alkylated ferrocenes in high yields (up to 87%). [ABSTRACT FROM AUTHOR]

Ferrocene is unique among organometallic compounds, and serves notably as a versatile platform towards the production of ligands useful to promote transition metals chemistry. A general limiting aspect of the synthesis of ferrocene derivatives is the efficient access to sophisticated highly functionalized polysubstituted ferrocenes, i.e. bearing four or more substituents replacing hydrogen atoms on the cyclopentadienyl rings. These ferrocene derivatives can bear various functional or/and structuring spectator substituents. Their preparation involves synthetic difficulties resulting from the need of multiple functionalizations coexisting altogether, and satisfying functional group compatibility and high selectivity issues. In the last decades, our group initially designed highly functionalized polyphosphines and hybrid ligands (1,1',3,3'‐tetrafunctionalized Fc) using dialkylated 1,1'‐tert‐butylferrocene as a scaffold, which opened the way to various new classes of hybrid compounds. Some of these original ferrocenes were used as ligands, promoting metal catalysed C–C and C–X bond formation (X = O, S, N, etc.). Thus, highly functionalized ferrocenes, which include notably (P,P,P,P)‐, (P,P,N,N)‐, (P,P,P')‐, (P,P,B)‐, (P,B)‐ and (N,B)‐compounds were developed in which the heteroatoms coexist in a close proximity on a common ferrocene platform with a controlled conformation. The present review details the concepts attached to the synthesis of these highly functionalized ferrocene species, and illustrates their main features and applications related to organometallic chemistry directed towards organic synthesis by metal catalysis. [ABSTRACT FROM AUTHOR]

Schematic representation of constructing CS-Fc@SPCE electrochemical immunosensor for the detection of cTnI. [Display omitted] • A label-free electrochemical immunosensor based on ferrocene derivatives amplified signal for cTnI detection was created. • A novel redox-active hybrid material, CS-Fc, which significantly increases the electron transfer rate. • The immunosensor showed excellent analytical performances in the assay of AMI warning biomarker – cTnI. As a biomarker of acute myocardial infarction (AMI), screening for cardiac troponin I (cTnI) has extremely high clinical sensitivity and specificity, and is extremely important for early intervention and risk assessment of AMI. Therefore, a novel redox-active hybrid material, CS-Fc, was synthesized by the Schiff base reaction of chitosan (CS) and ferrocene-carboxylic acid (Fc(COOH)) to form an amide group bonded together, which was used as a substrate-modified material for screen-printed carbon electrode (SPCE), and then assembled with an antibody (Ab), which was constructed into a label-free electrochemical immunosensor for the highly sensitive and rapid detection of cTnI in this study. The redox activity and biocompatibility of the highly stable and conductive composite CS-Fc significantly increased the effective specific surface area, electron transfer rate, and achieved effective amplification and specific analysis of the response signal. Under the optimized experimental conditions, the immunosensor showed a good linear relationship between its response signal and cTnI concentration in the range of 2.44 × 10−2 ∼ 2.50 × 101 ng mL−1, with a limit of detection (LOD) as low as 3.70 × 10−3 ng mL−1 (3σ, n = 11). Meanwhile, when used for the detection of cTnI in actual serum samples, it showed better reproducibility and stability, and the analytical results were better than those of the ELISA method, which indicated that it has a great potential for the accurate and rapid detection of cTnI in serum samples. In addition, it also provides a reliable means and scientific basis for process screening, early warning and prognostic risk assessment of AMI. [ABSTRACT FROM AUTHOR]

• New ferrocene carboranes with allyl substituents were prepared. • The formation of propenyl group due to the migration of allyl double bond was found. • Cyclic voltammetry data for allyl ferrocene m -carboranes were obtained. • New compounds were characterized by IR, NMR spectroscopy and mass spectrometry. A series of novel hybride ferrocene carborane derivatives containing allyl functionalities at the carborane carbon atoms were firstly synthesized in a good yield providing their potential applications in various fields of material science. Synthesized compounds were characterized using various spectroscopic techniques like IR, ESI-MS, 1H and 11B NMR data. Some compounds were investigated by cyclic voltammetry. The total charge density around each atom was calculated for 1-allyl-9-ferrocenylmethyl- m -carborane. Particular attention has been focused on the analysis of 1H NMR spectra of diallyl-substituted ferrocene carboranes which made it possible to discover the migration of the double bond in allyl substituent and the formation along with diallyl derivative of the corresponding allylpropenyl isomer compounds. [Display omitted] [ABSTRACT FROM AUTHOR]

New ferrocene derivatives as N-(3-piperidin-1-ylpropyl)ferrocenamide (Fc-3ppa) and N-(pyridine-3-ylmethyl)ferrocenamide (Fc-3pica) and structural investigations were carried out with 1H, 13C, DEPT 45 or 135, HETCOR, COSY NMR and FT-IR spectroscopic techniques. Characterization of Fc-3ppa (FeC19H26N2O) and Fc-3pica (FeC17H16N2O) was also supported by density functional theory (DFT) used by B3LYP functional and 6-31G(d) or 6-311++G(d,p) basis sets. From the combination of all the results, it can be clearly seen that syntheses of Fc-3ppa and Fc-3pica have been successfully achieved. Theoretical values are successfully compared against experimental data and B3LYP method is able to provide satisfactory results for predicting NMR properties and vibrational frequencies of the synthesized ferrocene based systems.

Eight ferrocene derivatives linked by either an ether, amine, or phenylacetylene moiety to a terminal ethynyl group were covalently deposited on glassy carbon electrodes by anodic electrochemical methods. The lithio activation method, in which the terminal hydrogen of the ethynyl group is replaced by a lithium atom before anodic oxidation, was successfully employed in all cases. Direct oxidation of the inactivated ethynyl group also resulted in surface deposition. Surface coverages between 1×10−10 mol cm−2 and 14×10−10 mol cm−2 were achieved. Cyclic voltammetry scans of the modified electrodes in pure electrolytes differed depending on the size of the supporting electrolyte anion, as little as half the current being measured for a [B(C6F5)4]− vs. [PF6]− solution, suggesting differences in ion transport near the electrode surface. An ether‐linked ethynylferrocenium ion (5+) was isolated after electrolytic and chemical oxidation of 5 and characterized by X‐Ray crystallography as its [SbCl6]− salt. [ABSTRACT FROM AUTHOR]

Although ferrocene derivatives have attracted considerable attention as possible anticancer agents, the medicinal potential of diiron complexes has remained largely unexplored. Herein, we describe the straightforward multigram‐scale synthesis and the antiproliferative activity of a series of diiron cyclopentadienyl complexes containing bridging vinyliminium ligands. IC50 values in the low‐to‐mid micromolar range were determined against cisplatin sensitive and resistant human ovarian carcinoma (A2780 and A2780cisR) cell lines. Notable selectivity towards the cancerous cells lines compared to the non‐tumoral human embryonic kidney (HEK‐293) cell line was observed for selected compounds. The activity seems to be multimodal, involving reactive oxygen species (ROS) generation and, in some cases, a fragmentation process to afford monoiron derivatives. The large structural variability, amphiphilic character and good stability in aqueous media of the diiron vinyliminium complexes provide favorable properties compared to other widely studied classes of iron‐based anticancer candidates. [ABSTRACT FROM AUTHOR]

Ferrocene derivatives are considered as representative outer‐sphere redox couples that do not specifically interact with the electrode surface. It, however, is highly challenging to unambiguously prove their outer‐sphere character experimentally. Herein, we employ quantitative cyclic voltammetry to assess whether ferrocene carboxylates and sulfonates mediate only outer‐sphere electron transfer (ET) at highly oriented pyrolytic graphite (HOPG). We find voltammetrically that only reduced forms of ferroceneacetate, ferrocenecarboxylate, and ferrocenesulfonate are specifically adsorbed on the HOPG surface to mediate outer‐sphere ET without inner‐sphere ET, which requires the adsorption of both reduced and oxidized forms of a redox couple. By contrast, no voltammetric feature of adsorption is observed for 1,1′‐ferrocenedicarboxylate and 1,1′‐ferrocenedisulfonate to prevent us from identifying the unique mechanism among outer‐sphere ET, inner‐sphere ET, and both owing to the Laviron‐Amatore paradox. [ABSTRACT FROM AUTHOR]

This work addresses the effects of supramolecular complexation by cucurbit[7]uril (CB[7]) on the cell potential of aqueous batteries based on ferrocene and 4,4′‐bipyridinum (viologen) electroactive materials. It was previously known that the oxidation potential of cationic ferrocene derivatives is shifted to more positive values by the formation of highly stable 1 : 1 binary complexes with CB[7]. Here, we found that the formation of 1 : 2 ternary complexes between suitably designed viologens and CB[7] leads to a pronounced shift to more negative values in the first one‐electron reduction potential of the viologen. Combining these two effects, we predict that the corresponding aqueous redox flow battery (RFB) ‐containing cationic ferrocene in the catholyte and viologen in the anolyte‐ will exhibit a potential of 1.04 V in the absence of CB[7] and 1.30 V in the presence of suitable concentrations of CB[7]. This substantial potential increase might be improved in future research, as the supramolecular complexation effect seems to be rather general. [ABSTRACT FROM AUTHOR]

His‐tagged molecular species, a ferrocene derivative and Protein A, were immobilized on electrode surfaces (Au and graphite) through formation of a chelated complex in the presence of Cu2+ cations used as bridging units. The complex was cleaved and the attached molecules were released from the electrode surface by applying reductive potential to the electrodes resulting in Cu2+ reduction, thus decomposing the chelate complex. The molecule release process was followed by cyclic voltammetry in case of the ferrocene derivative. His‐tagged Protein A was additionally labeled with a fluorescent tag and its release was followed by fluorescence measurements in the solution and by impedance spectroscopy at the electrode. The studied release of the His‐tagged redox species and biomolecules was considered as a new generic approach to the signal‐controlled molecule release applicable in various biotechnological and biomedical applications. [ABSTRACT FROM AUTHOR]

• Ferrocene derivatives are active agents against sundry of infectious diseases. • Important conjugates are listed with the corresponding IC 50 values. • Approved drugs and ferrocene derivatives are compared regarding their mode of action. • Ferrocene leads to ROS generation and subsequent lipid, protein and DNA oxidation. • The anti-malarial drug ferroquine is currently in clinical trials. Infectious diseases like malaria, tuberculosis or HIV are among the leading causes of death worldwide according to WHO estimations. Nevertheless, the fight against infectious diseases is aggravated through growing development of resistance towards current drugs and due to their severe adverse effects. The introduction of the lipophilic organometallic moiety ferrocene, a compound with a sandwich-like structure, in an existing bioactive molecule is a promising tool for the development of new more efficient drugs with innovative mechanisms of action. Thus, this review summarizes recent developments in the field of ferrocene conjugation to bioactive molecules like natural products, synthetically derived drugs, peptides as well as heterobimetallic complexes. Hereby, we will provide the reader with a summary of the most potent ferrocene derivatives reported for a plethora of infectious diseases by tabulating and critically assessing the corresponding IC 50 values and the minimal inhibitory concentrations (MIC). Owing to the diverse field of infectious diseases the reported ferrocene derivatives were classified according to their targets into four main groups: antiparasitic (with antimalarial agents as biggest group), antibacterial, antifungal and antiviral agents. [ABSTRACT FROM AUTHOR]

Optoelectronic and charge transfer properties of three ferrocene derivatives 4-(4-methoxybenzyl)-1-(1-ferrocenylethyl)thio-semicarbazone (1), 4-(2-fluorobenzyl)-1-(1-ferrocenylethyl)thiosemicarbazone (2) and 4-(3,4-dimethylphenyl)-1-(1-ferrocenylethyl)thiosemicarbazone (3) were probed by first-principles study. Density functional theory (DFT) was carried out to elucidate the structural and electronic properties. The B3LYP/6-31G**(LANL2DZ) level was adopted to shed light on the structural parameters and frontier molecular orbitals. The computed geometrical parameters are rationale to the X-ray crystallographic data. The intra-molecular charge transfer from ligand to metal was perceived in ferrocene derivatives. The absorption and emission spectra were computed employing time domain TD-B3LYP/6-31G** (LANL2DZ) level. The hole and electron transfer integrals were estimated to figure out the charge transfer nature in particular ferrocene derivatives. The larger electron transfer integral values are anticipating that these studied Compounds 1–3 might be better electron transfer materials. Moreover, the effect of electron activating groups (–CH3 and –OCH3) and electron deactivating group (-F) was studied on the transfer integrals, structural and electro-optical properties. [ABSTRACT FROM AUTHOR]

Synthesis and characterization of 4-ferrocenylphthalazin-1(2Н)-one and 4-cymantrenylphthalazin-1(2H)-one are studied. All ferrocene derivatives undergoes a reversible one-electron oxidation, localized presumably at the ferrocene unit. Solvothermal conditions of organometallic phthalazin-1(2H)-ones have been optimized. o- Ferrocenylcarbonylbenzoic acid (η5-C 5 H 5)Fe(η5-C 5 H 4 C(O)C 6 H 4 COOH) (I) and o- cymantrenylcarbonylbenzoic acid (II) were obtained from ferrocene or (η5-C 5 H 5)Mn(CO) 3 , respectively, by the Friedel–Crafts reaction with phthalic anhydride. Methyl o -ferrocenylcarbonylbenzoate (η5-C 5 H 5)Fe(η5-C 5 H 4 C(O)C 6 H 4 COOMe (III) and methyl o -cymantrenylcarbonylbenzoate (CO) 3 Mn(η5-C 5 H 4 C(O)C 6 H 4 COOMe) (IV) were synthesized from I and II, respectively using dimethyl carbonate (DMC) in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) to promote the methylation reaction. 4-Ferrocenylphthalazin-1(2H)-one (V) and 4-cymantrenylphthalazin-1(2H)-one (VI) were obtained by the interaction of hydrazine hydrate with I and II, respectively, by the prolonged reflux or convenient solvothermal synthesis. Cyclic voltammetry measurements showed that compounds III and V undergo reversible one-electron oxidation, localized presumably at the ferrocene unit. For III the irreversible one-electron oxidation is apparently associated with the oxidation of the benzoate fragment. All new compounds were characterized by spectroscopic methods and the molecular structures of II and III were determined by X-ray diffraction analysis. [ABSTRACT FROM AUTHOR]

An efficient procedure able to deliver grams of racemic and enantioenriched 2-iodo- N , N -diisopropylferrocenecarboxamide without chromatographic purification was developed. To introduce the halogen, two procedures, one using the n BuLi-TMEDA chelate and one using a lithium amide in the presence of ZnCl2 as in situ trap were developed. Further functionalization by Suzuki–Miyaura and Ullman-type cross-couplings was investigated to access a variety of ferrocene derivatives. [ABSTRACT FROM AUTHOR]

• Basic switching mechanisms of resistive memory devices are introduced. • Much progress has been made in resistive memory switching using metal complexes. • The control of resistive switching properties by ligand design is discussed. Transition-metal complexes (TMCs) have recently attracted considerable scientific interest for resistive memory switching. The interplay between metal ions and ligand endows TMCs with rich and tunable electrochemical and photophysical properties, making them beneficial for the formation of electrical bi- or multistates in resistive memory devices. This review summarizes the applications of TMCs in resistive memory switching. Following the simple introduction of the basic concept and switching mechanism of resistive memory devices, the recent progress on the applications of ferrocene derivatives, polyazine metal complexes and metallopolymers, alkynyl metal complexes, and porphyrin or phthalocyanine metal complexes are discussed, with an emphasis on the modulation or control of switching properties by ligand design. [ABSTRACT FROM AUTHOR]

A new ferrocene based receptor 1,2-bis(ferrocenylmethylthio)-maleonitrile (FcMNT) was synthesized and characterized by elemental analysis, FTIR, NMR and X-ray single crystal diffraction. The ligand showed a high selection for Hg2+ in DMF or DMF/H 2 O mixed solution. Upon addition of Hg2+ in DMF, the receptor showed an obvious color change and significant UV–vis spectroscopic response. Electrochemical titrations revealed that the receptor sensed Hg2+ in high selectivity with an anodic shift of 307 mV. The 13CNMR titrations confirmed that the Hg2+ interacted with the S atoms of FcMNT when the amount of Hg2+ was under 1.0 equiv.; the Hg2+ interacted with C C and C N groups when the amount of Hg2+ was above 1.0 equiv. A new ferrocene based receptor 1,2-bis(ferrocenylmethylthio)-maleonitrile (FcMNT) was synthesized and characterized. The ligand shows high a sensitivity and selectivity towards mercury ions in DMF and DMF/H 2 O solution. Unlabelled Image • A new maleonitrile dithiolate modulated bis-ferrocene ligand was synthesized and characterized. • The ligand showed a high sensitivity and selectivity to Hg2+. • The sensing mechanism between FcMNT and Hg2+ was confirmed through 13CNMR titrations. [ABSTRACT FROM AUTHOR]

Abstract Four ferrocene-based D-π-A dyes with effective intramolecular charge transfer (ICT) properties are designed and synthesized. These dyes can be used as new photoredox catalysts in free radical photopolymerization under soft blue and green LED irradiations. Different π-conjugation bridge molecules contained in the molecular structures have been shown to affect the photoreactivities of the synthesized dyes in the photoinitiating systems. The UV–Vis absorption, electrochemical, and third-order nonlinear optical properties are investigated. Experimental results are completed with theoretical calculations to gain further insight into the ICT of the dyes with different π-conjugation bridge molecules. A good correlation of the π-conjugation bridge molecule changes of the dyes with the experimental results is established. Graphical abstract Ferrocene based D-π-A dyes as novel photoredox catalysts in photopolymeization under soft visible LED irradiations. Image 1 Highlights • Four ferrocene-indanone organometallic dyes are designed and synthesized. • The dyes exhibit effective ICT characters and show good nonlinear absorption properties. • A good correlation of experimental and theoretical results is established. • The dyes can be used as photoredox catalysts in photopolymerization under LED irradiations. [ABSTRACT FROM AUTHOR]

DFT calculations were used to capture the properties of redox-switchable metal complexes relevant to the ring-opening polymerisation of cyclic esters by varying the metals, donors, linkers, and substituents in both accessible ferrocene oxidation states. A map of this chemical space highlights that modifying the ligand architecture and the metal has a larger impact on structural changes than changing the oxidation state of the ferrocene backbone. [ABSTRACT FROM AUTHOR]

Abstract Two new complexes, [Zn 2 Cl 4 (Fcdpa) 2 ·CH 2 Cl 2 ] n (1) and [CdI 2 (Fcdpa)] n (2) (Fcdpa = N , N -di(4-pyridyl)animomethylferrocene) have been successfully synthesized. The ligand Fcdpa and their metal complexes are characterized by elemental analysis, IR, 1HNMR, PXRD and electrochemistry. Single crystal X-ray diffraction analysis reveals that the metal ions are bridged by Fcdpa ligands to generate one dimensional chain in both complexes 1 and 2. Electrochemical investigation reveals that the redox peaks of Fcdpa , 1 and 2 are similar. Graphical abstract A new ferrocene-based ligand, and its Zn(II) and Cd(II) complexes were synthesized and characterized. The monosubstituted dipyridine ferrocene derivative is a useful building block for constructing 1D complexes. Their structures and electrochemical properties have been studied in detail. Unlabelled Image Highlights • A new monosubstituted dipyridine ferrocene ligand and its Zn(II) 1 and Cd(II) 2 complexes have been synthesized. • The structure of the ligand and the complexes are determined by X-ray study. • The metal ions in the two complexes are connected by the ligand to generate 1D chain, respectively. • Electrochemical properties of the ligand and the two complexes are investigated. [ABSTRACT FROM AUTHOR]

Abstract To establish highly soluble single redox couple for non-aqueous flow batteries, N -(α-ferrocenyl)ethylphthalimide (α-FcEtPI) is derived from a promising single redox couple, N -ferrocenylphthalimide (FcPI), by inserting an α-methyl group between the ferrocenyl and phthalimide moieties. The resulting material (α-FcEtPI) shows the maximum solubility of 0.81 M in 1.0 M tetrabutylammonium tetrafluoroborate (TBABF 4) in 1,3-dioxolane at 25 °C. This notable increase in solubility (versus 0.3 M for FcPI) is attributed to the disruptive effect of the α-methyl group on molecular packing in a solid state. α-FcEtPI exhibits two stable redox reactions at E 1/2 = 0.01 V and −1.97 V (vs. Fc/Fc+), thus functioning as a single redox couple with working voltage (E wk) of 1.98 V. Considering the solubility and working voltage, the theoretical energy density of α-FcEtPI is calculated as 21.06 W h L−1 (versus 7.8 W h L−1 for FcPI). The cell data of 0.6 M α-FcEtPI in 1 M TBABF 4 in 1,3-dioxolane electrolytes, indicates remarkably high Coulombic efficiency (97.8%) and excellent cycle retention. Highlights • N -(α-ferrocenyl)ethylphthalimide (α-FcEtPI): single redox couple with α-methyl link. • α-methyl link lowers packing density to increase solubility up to 0.81 M • α-FcEtPI exhibits two redox reactions at E 1/2 = 0.01 V and −1.97 V (vs. Fc/Fc+). • Theoretical energy density of non-aqueous flow cell calculated as 21.06 Wh L−1. • Cell data shows stable cycleability even in highly concentrated α-FcEtPI (0.6 M). [ABSTRACT FROM AUTHOR]

In this contribution we report the synthesis of the novel unsymmetrical ferrocene‐based pincer‐type proligand η5‐CpFeη5‐C5H2‐1‐Br‐2‐PPh2‐5‐CH2NMe2 (1). Its reactivity is demonstrated by isolation of related organotin derivatives η5‐CpFeη5‐C5H2‐1‐SnR3‐2‐PPh2‐5‐CH2NMe2 (3, R = Ph; 4, R = Me). The reactions of compounds 3 and 4 with H2O2 and elemental sulfur gave the corresponding ferrocenylphosphane oxide (5) and the sulfides (6, 7), respectively. Most remarkably, an unprecedented reaction of the organotin derivative 3 with elemental iodine was observed, providing the ammonium salt [η5‐CpFeη5‐C5H2‐1‐SnPh2I‐2‐P(O)Ph2‐5‐CH2NHMe2]I (8). The compounds are characterized by elemental analyses, 1H, 13C, 31P, 119Sn NMR spectroscopy, electrospray ionization mass spectrometry, and single‐crystal X‐ray diffraction analyses (3–8). Also reported are the solid‐state structures of the hydrolysis products [η5‐CpFeη5‐C5H2‐1‐SnPh2(OH)‐2‐P(O)Ph2‐5‐CH2NHMe2]·0.5H2O (9a) and [η5‐CpFeη5‐C5H2‐1‐SnPh(OH)‐2‐P(O)Ph2‐5‐CH2NMe2]2[I3]2 (9b) that were isolated by serendipity. No pincer‐type behaviour is observed for the ferrocene derivative 5 and related compounds as only one out of the two donor sites coordinates the tin atom. The high basicity of the aminomethyl nitrogen atom promotes easy hydrolysis of the organotin halide derivatives giving ammonium salts such as 8 and 9a. N···H···O hydrogen bridge outperforms intramolecular N→Sn interaction. [ABSTRACT FROM AUTHOR]

Abstract In this paper, ferrocene derivative polymer nanoparticles (FcP NPs) with uniform size and good photostability was synthesized using 1,1′-ferrocene dicarboxylic acid as precursor and methanol as solvent. FcP NPs-PDA was further obtained by coating of polydopamine (PDA) on FcP NPs in tris-HCl (pH=8.5) buffer solution at room temperature in the presence of dopamine (DA). The structure and morphology of FcP NPs and FcP NPs-PDA were characterized by transmission electron microscope (TEM), ultraviolet-visible spectroscopy (UV–Vis), and infrared radiation (FT-IR). The as-prepared FcP NPs-PDA showed better peroxidase-like activity than FcP NPs, which could catalyze the chromogenic reaction of peroxidase substrate TMB, OPD and ABTS. Based on the high peroxidase-like property of FcP NPs-PDA, a sensitive and convenient means to detect H 2 O 2 has been proposed with TMB as the substrate, which displays wide linear range of 10–600 μM and 600 μM-4 mM with low detection limit of 5 μΜ. Compared with other Fe-containing NPs, such as magnetic materials and noble metal@Fe bimetallic NPs, the preparation approach for FcP NPs-PDA is simple, time and energy saving and environment friendly. This mild and simple synthesis route of FcP NPs-PDA will provide new ideas for the preparation of non-noble metal-based peroxidase-like nanomaterials and widen the applications in the fields of catalytic and analytical chemistry. Graphical abstract fx1 Highlights • Ferrocene derivative polymer NPs functionalized with PDA was developed. • The FcP NPs-PDA showed good peroxidase-like activity. • This study is the first attempt to prepare ferrocene derivatives nanoparticles for colorimetric. • The preparation for FcP NPs-PDA is simple, time and energy saving and environment friendly. • This study can expand the application of ferrocene derivatives in the field beyond electrocatalysis. [ABSTRACT FROM AUTHOR]

Abstract Electron transfer (ET) constitutes a key process for several biological transformations, including solar energy conversion in bacteria and plants. Nowadays, numerous synthetic systems have been proposed to mimic such kind of natural occurring process. In this work, we elucidate the factors that mostly influence the electron transfer process in ferrocene-naphthoquinone dyads. In particular, the connection between the two redox units has been varied, in order to study the ET dependence from: i) the distance between donor-acceptor units and ii) the oxidation potential of the donor species. No interaction among the two moieties has been detected at the ground state, while efficient electron transfer process was observed following excitation of the naphthoquinone through UV-light, as well as upon the aid of a Lewis acid promoter in solution. Moreover, DFT calculations have been performed to support the experimental data. Graphical abstract Image 1 Highlights • Elucidation of electron transfer process in ferrocene-naphthoquinone dyads. • ET dependence from the distance between donor-acceptor units. • ET dependence from the oxidation potential of the donor species. • Lewis acid promoter in solution (Sc3+) helps the ET. [ABSTRACT FROM AUTHOR]

Highlights • A novel core-shell SiO 2 @Fc(COCH 3) 2 nanospheres is designed for electrochromism. • The SiO 2 @Fc(COCH 3) 2 films with adjustable porosity were prepared. • The effect of the porosity on electrochromic properties is investigated. • The porosities of the films are solved numerically by the finite-element method. Abstract Although the properties of electrochromic materials (ECMs) have been enhanced using fabricated porous materials, the effect of materials porosity on such an enhancement remains unclear. Here, we report a novel ECMs with an adjustable pore hierarchy based on quasi-amorphous and ordered arrays of SiO 2 @Fc(COCH 3) 2. ECMs with different pore systems were generated by modifying Fc(COCH 3) 2 concentration and self-assembly temperature. The composition and core-shell structure of the SiO 2 @Fc(COCH 3) 2 nanospheres were confirmed through scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FT-IR) and EDX mapping. The influence of adjustable pore system on the electrochemical behavior was studied. Experimental results showed that the current density of the redox couple peaks of the quasi-amorphous porous SiO 2 @Fc(COCH 3) 2 films are considerably lower than those of the ordered porous films but are higher than those of the dense Fc(COCH 3) 2 films. At 550 nm, the transmittance variation of the quasi-amorphous porous SiO 2 @Fc(COCH 3) 2 film is 19%, whereas that of the ordered porous film is 35%. The coloration and bleaching times of the quasi-amorphous porous SiO 2 @Fc(COCH 3) 2 film are 17.1 s and 4.5 s, respectively, whereas those of the ordered porous film are only 16.5 s and 3.5 s, respectively. Furthermore, the porosities of the films are solved numerically by the finite-element method. For the ordered porous SiO 2 @Fc(COCH 3) 2 film, the porosity is 0.26, while the quasi-amorphous film became larger (0.31–0.41). This work is the first step in combining ferrocene derivative and colloidal crystal porous structures to develop a green, simple and efficient electrochromic process. [ABSTRACT FROM AUTHOR]

Two exemplary contributions of organometallics in medicinal chemistry, ferroquine and ferrocifen, which exhibit excellent anti-plasmodial and anti-cancer activities, respectively, have opened a new field called medicinal organometallic chemistry. This field has been gaining significant interest due to the recent upsurge in ferrocene-linked organic frameworks with promising biological potential. The success of ferrocene is due to the sustained efforts by organic medicinal chemists and its inherent stability in air, heat and light, low toxicity, low cost and reversible redox properties. The replacement of the aryl/heteroaryl core with a ferrocene nucleus in organic molecules imparts a significant change not only in their molecular properties, such as solubility and hydro-/lipophilicity, but also improves the activities of bioactive compounds. Ferrocifen (ferrocene analogue of hydroxytamoxifen) possesses the remarkable feature of being anti-proliferative against both the MCF-7 (hormone dependent) and MDA-MB-231 (hormone independent) breast cancer cell lines. Accordingly, this review article is aimed at updating researchers on the recent developments (2014–18) on the synthesis and evaluation of ferrocene-containing bio-active pharmacophores with emphasis on their structure–activity relationship and mechanism of action. [ABSTRACT FROM AUTHOR]

The purpose of the current research was to construct an intermediate (2-(4-Ferrocenyl-[1,2,3]triazol-1-yl)-1-(naphthalen-2-yl) ethanone (2FTNE)) and a magnetic core-shell manganese ferrite nanoparticle (CMNP) to synthesis a modified carbon paste electrode (CPE). The electrochemical behavior of epinephrine (EP) was assessed by cyclic voltammetry and measured by square wave voltammetry by exposing to uric acid (UA) and folic acid (FA). High electrocatalytic activity for EP oxidation was seen in the 2FTNECMNP-modified CPE (2FTNEMCNPPE) compared to only CPE- and MCNP-modified CPE. The oxidation peak current of EP was linear within the range of 0.05-60 μM and its correlation coefficient was 0.999. The limit of detection was calculated at 0.016 μM for EP based on three times the standard deviation (3Sb) of the blank. According to the results, high selectivity, proper stability and good reproducibility was observed for the 2FTNEMCNPPE that detected EP, UA and FA successfully in an EP ampule, a folic acid tablet and urine samples, introducing 2FTNEMCNPPE with high capacity to develop the electrochemical sensors. [ABSTRACT FROM AUTHOR]

Abstract Herein, we present the primary results on two valuable E-Z stereoisomers containing ferrocene scaffold [(E)-5,5-dimethyl-3-oxo-2-(2-phenyl-2-ferrocenyl-vinyl)cyclohex-1-en-1-yl acetate (E-FerCycAc) and its Z-stereoisomer (Z-FerCycAc)]. These compounds were both prepared from 1-phenylvinyl-ferrocene and 5,5-dimethyl-1,3-cyclohexanedione under catalysis of manganese(III) acetate according to the radical addition mechanism. The prominent spectroscopic data of the target stereoisomers were provided by FT-IR, LC-MS, 1H NMR, 13C NMR techniques, and their stereochemical identification was made primarily by NOESY analysis. The corresponding data (absorbance, transmittance and optical and transport energy gap) were collected from UV– vis studies. The optical properties of the glass slides coated with E-FerCycAc and Z-FerCycAc films were examined and consequently, the optical and transport energy band gap values of the E-FerCycAc were found significantly lower than Z-FerCycAc. The physicochemical and spectroscopic findings (HOMO-LUMO energies, bandgap values, UV– vis , FT-IR, 1H, and 13C NMR spectra) were also compared and supported with the acquired DFT calculations. Graphical abstract Image 1 Highlights • Two newly designed E/Z-stereoisomers containing ferrocene subunit were successfully prepared. • The optical properties of the stereoisomers were evaluated via experimental and theoretical UV– vis studies. • The E-isomer has shown better than Z-isomer optical performance and can be considered a suitable candidate for further studies as photovoltaic material. [ABSTRACT FROM AUTHOR]

Voltage‐stimulated redox‐active materials have received significant attention in the field of organic electronics and sensor technology. Such stimuli‐responsive materials trigger the formation of crystalline nanostructures and facilitate the design of efficient smart devices hitherto unknown. Herein, we report that free‐base and metallo‐tetratolylporphyrin‐linked ferrocene derivatives (H2TTP‐Fc and ZnTTP‐Fc) undergo distinct proton/anion binding mechanism in CHCl3 during bulk electrolysis at applied voltage of 1.4 V to give [H4TTP‐Fc]+Cl− and H+[(Cl)ZnTTP‐Fc]− followed by nanospheres and crystalline 2D nanoflakes formation, confirmed by SEM and TEM images, by methanol vapor diffusion (MVD) approach. Moreover, X‐ray diffraction analysis suggest that protonated H2TTP‐Fc aggregates exhibit amorphous nature, whereas H+[(Cl)ZnTTP‐Fc]− depict crystalline nature from layer‐by‐layer arrangement of nanoflakes assisted by π–π stacking and ion‐dipole interactions. Crystalline 2D Nanoflakes: Voltage‐responsive H2TTP‐Fc and ZnTTP‐Fc demonstrate cation (H+)/anion (Cl−) binding affinity towards free "N" atoms and Zn in CHCl3, leading to [H4TTP‐Fc]+Cl− and H+[(Cl)ZnTTP‐Fc]−. Further, bulk electrolysis of [H4TTP‐Fc]+Cl− and H+[(Cl)ZnTTP‐Fc]− at 1.4 V leads to the formation of nanospheres and crystalline 2D nanoflakes by methanol vapor diffusion (MVD) approach. [ABSTRACT FROM AUTHOR]

Abstract Chemical oxidation of ferrocene and related derivatives by dibenzoyl peroxide in acetonitrile solution produces ferrocenium and benzoic acid after acidification. The rate law is first order in oxidant and in reductant. Steric effects and activation parameters are consistent with a rate-controlling outer-sphere single-electron transfer (ET) step, and reorganization energies are obtained using Marcus theory with B3LYP calculations. Energetics, optimized structures, and solvent effects indicate that rate is affected more by anion than cation solvation and that oxidation of decamethylferrocene by 3-chloroperoxybenzoic acid does not occur by ET. Graphical abstract Image 1 Highlights • RFc derivatives react with DBP at rates first order in each reactant. • Steric effects of RFc substituents on k are small even for (Cp*) 2 Fe. • Electron-donating abilities of RFc substituents correlate with increasing k. • Activation parameters, Marcus theory, DFT, and solvent effects are examined. • Outer-sphere single-electron transfer occurs with DBP, but not mCPBA. [ABSTRACT FROM AUTHOR]

Metal-organic frameworks (MOFs) exhibit structural diversity and functional tunability, rendering them a versatile platform for a wide range of applications. Specifically, defects or function groups induced by exotic ligands is an efficient strategy to adjust the catalytic performance. In this study, we explore the impact of incorporating ferrocene derivatives into two Ni-based MOFs and examine their suitability as potential glucose sensors. One strategy involves introducing bidentate 1,1′-ferrocenedicarboxylic acid (1,1′-Fc) into the 3D Ni-1,4-benzenedicarboxylic acid MOF (Fc-Ni-BDC) using a simple single-step hydrothermal method. Another approach involves encapsulating ferrocenemethylamine (Fc-NH 2) inside the cavity of 2D conductive Ni-HHTP MOF (HHTP=2,3,6,7,10,11-hexahydroxytriphenylene) driven by electrostatic attraction to form Fc-Ni-HHTP. On account of the synergy between ferrocene derivatives and MOFs, the hybrid MOFs demonstrated remarkable electrochemical performance, characterized by pronounced electrocatalytic reactivity towards glucose oxidation. It is showed that the doped ferrocene derivatives act as electron donors to the MOF active sites, modifying the electronic structure and facilitating the kinetics of the reactions, then an augmentation in the catalytic efficiency has been achieved. This work demonstrates a simple strategy to improve MOF-based electrochemical sensors by incorporating metallocene ligands. [Display omitted] [ABSTRACT FROM AUTHOR]

In our work, the fluorescent molecule ((1E)-1-((4-(1,2,2-triphenylvinyl)benzylide-ne)hydrazineylidene)ethyl)ferrocene (FcMe-TPE) with aggregation-induced emission (AIE) property and redox activity was synthesized. The fluorescence intensity of FcMe-TPE assembly could be modulated by changing solvent, adding oxidant or applying voltage. At the same time, the translation mechanism was explored in detail by means of density functional theory (DFT). [Display omitted] • The fluorescence behavior of FcMe-TPE could be modulated by changing solvent, adding oxidant or applying voltage. • A adjustable competitive hydrogen bonding interaction between methyl group, DMF and water was found. • The fluorescence translation mechanism was studied in detail by quantum chemistry calculation. • The assemblies of FcMe-TPE molecule were successfully used to make electrofluorochromic device with small trigger voltage. Stimuli-responsive supramolecular materials have attracted much attention because of their controllable microstructure and luminescence behavior. In this study, the fluorescent molecule ((1E)-1-((4-(1,2,2-triphenylvinyl)benzylidene)hydrazineylide-ne)ethyl)ferrocene (FcMe-TPE) with aggregation-induced emission (AIE) property and redox activity was synthesized. The morphology as well as fluorescence behavior could be modulated by changing solvent, adding oxidant or applying voltage, and the translation mechanism was explored in detail by means of density functional theory (DFT). Based on the presence of competitive hydrogen bonding, FcMe-TPE assemblies showed different aggregate behaviors and properties under different water contents (f w). As f w increased from 20% to 60%, the morphology of assemblies could be transformed from 2D sheet to elliptical crystal structure, then the precipitation gradually disappeared for the further increase of f w. At the same time, the addition of oxidant as well as the application of voltage could also cause changes in the fluorescence intensity of the assemblies. When the voltage increased from 0 V to 3 V, the fluorescence intensity increased and reached the maximum value at 1 V. Based on this property, the electrofluorochromic (EFC) device with low trigger voltage was made. This work provides a feasible strategy for controllable self-assembly and the fabrication of multiple fluorescence switches, which has potential practical application in the field of advanced anti-counterfeiting, intelligent display and information encryption. [ABSTRACT FROM AUTHOR]

• New ferrocene functionalized chiral secondary amines. • Propensity of molecules to form diverse supramolecular assembly through NH...O, CH...O and CH...I hydrogen bonding. • In vitro anti-proliferative study against MCF 7, IMR 32, HepG2 and L132 cell lines. • Dependence of anti-proliferative activity on chirality and redox potentials. • In-silico study to rationalize the results. Chiral α-iodoamides (S)-IA- 1 , (R)-IA- 2 , (S)-IA- 3 and (R)-IA- 4 were synthesized and characterized prior to use in the synthesis of four chiral ferrocenyl secondary amines viz. (S)-2-(ferrocenylmethylamino)- N -(1-phenylethyl)acetamide, (S)-FA- 5 , (R)-2-(ferrocenyl methylamino)- N -(1-phenylethyl)acetamide, (R)-FA- 6 , (S)-2-(ferrocenylmethylamino)- N -(1-(naphthalen-1-yl)ethyl)acetamide, (S)-FA- 7 and (R)-2-(ferrocenylmethylamino)- N -(1-(naphthalen-1-yl)ethyl)acetamide, (R)-FA- 8. The purity and composition of the compounds were ascertained by elemental, 1H, 13C NMR, FTIR, UV–visible emission spectral and X-ray diffraction methods. The formation of diverse supramolecular assemblies sustained by several NH...O, CH...O and CH...I intermolecular hydrogen bonding interactions was confirmed by single crystal X-ray diffraction (SCXRD). The impact of Eh and chirality on the anti-proliferative activity of these compounds has been explored. Notably, R-enantiomers are found to be superior to S-enantiomers in the studied MCF 7, IMR 32, HepG2 and L132 cell lines of human origin. In instance, (R)-FA- 6 has demonstrated superior activity than cisplatin against MCF 7 (IC 50 : 31.38±0.24 μM) and HepG2 (IC 50 : 18.78±0.14 μM). Further research, including electrochemical, DFT calculations and a docking analysis, was performed to rationalize and confirm the results. [Display omitted] [ABSTRACT FROM AUTHOR]

Spectrophotometrical technics based assay were developed for the calculation of binding parameters like binding constant, ratio of binding constants and binding free energy of two potential antioxidants 2-(ferrocenylmethylamino)benzonitrile (2FMAB) and 3-(ferrocenylmethylamino)benzonitrile (3FMAB) with 1,1-diphenyl-2-picrylhydrazyl radicals (DPPH). 3FMBA shows highest binding constant and highest binding free energy (2.28×10-5 M-1) and (30.06 KJmol-1) respectively. Binding free energy of DPPH-3FMAB is three times greater than that of the standard antioxidant ascorbic acid (10.93 KJmol-1).

The fascinating electrochemical properties of the redox-active compound ferrocene have inspired researchers across the globe to develop ferrocene-based electrocatalysts for a wide variety of applications. Advantages including excellent chemical and thermal stability, solubility in organic solvents, a pair of stable redox states, rapid electron transfer, and nontoxic nature improve its utility in various electrochemical applications. The use of ferrocene-based electrocatalysts enables control over the intrinsic properties and electroactive sites at the surface of the electrode to achieve specific electrochemical activities. Ferrocene and its derivatives can function as a potential redox medium that promotes electron transfer rates, thereby enhancing the reaction kinetics and electrochemical responses of the device. The outstanding electrocatalytic activity of ferrocene-based compounds at lower operating potentials enhances the specificity and sensitivity of reactions and also amplifies the response signals. Owing to their versatile redox chemistry and catalytic activities, ferrocene-based electrocatalysts are widely employed in various energy-related systems, molecular machines, and agricultural, biological, medicinal, and sensing applications. This review highlights the importance of ferrocene-based electrocatalysts, with emphasis on their properties, synthesis strategies for obtaining different ferrocene-based compounds, and their electrochemical applications., (© 2023. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

Alkylferrocene‐based burning‐rate catalysts (BRCs) exhibit distinct migration tendency and high volatility and thus result in inferior performance of composite solid propellants during their combustion processes. To deal with these drawbacks, a novel dinuclear nitrogen‐rich ferrocene derivative, 4‐amino‐3,5‐bis(4‐ferrocenyl‐1,2,3‐triazolyl‐1‐methyl)‐1,2,4‐triazole (BFcTAZ) and its twenty seven ionic coordination compounds, [M2(BFcTAZ)2(H2O)4]mXn·xH2O (M = Cr3+, Mn2+, Fe3+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+ and Pb2; X = polycyano anions), were synthesized and characterized by FT‐IR, UV/Vis, and elementary analysis. Crystal structure of BFcTAZ was further confirmed by single‐crystal X‐ray diffraction and a general molecular structure of the new complexes was proposed. Their high thermal stability was verified by TG technique. Cyclic voltammetry studies suggested that the new compounds are diverse redox systems. Their effects on the thermal degradation of some common oxidizers were measured by DSC technique. The results indicated that most of the new complexes exert great effects on the thermal decomposition of AP, RDX, and 1,1‐diamino‐2,2‐dinitroethylene (FOX‐7) and some of them are more active than catocene. The Cu2+ complexes are among the excellent ones. However, only six compounds have appreciable catalytic activity in the thermal degradation of HMX. [ABSTRACT FROM AUTHOR]

Graphical abstract This paper describes the synthesis of a ferrocene based bisphosphine ligand, 1,1′-bis(diphenylethynylphosphino)ferrocene, its reactivity and transition metal complexes of Mo0, W0, RuII, PdII PtII, CuI and AuI. 1,1′-Bis(diphenylethynylphosphino)ferrocene show both chelating as well as bridged bidentate modes of coordination. Abstract The new ferrocene based bisphosphine [Fe{C 5 H 4 P(C CPh) 2 } 2 ] (1) was synthesized in 82% yield by the treatment of bis(dichlorophosphino)ferrocene [Fe(C 5 H 4 PCl 2) 2 ] with four equivalents of lithium phenylacetylide. The reactions of 1 with aq. H 2 O 2 , elemental sulfur or selenium afforded bis(chalcogenide) derivatives, [Fe{C 5 H 4 P(E)(C CPh) 2 } 2 ] (2 E = O, 3 E = S, 4 E = Se). The reaction of 1 with [M(NC 5 H 11) 2 (CO) 4 ] (M = Mo, W), [RuCp(PPh 3) 2 Cl] and [M(COD)Cl 2 ] (M = Pd, Pt) resulted in the formation of the respective chelate complexes, [Fe{C 5 H 4 P(C CPh) 2 } 2 {M(CO) 4 }] (5 M = Mo, 6 M = W), [Fe{C 5 H 4 P(C CPh) 2 } 2 {RuCp(Cl)}] (8) and [Fe{C 5 H 4 P(C CPh) 2 } 2 {MCl 2 }] (9 M = Pd, 10 M = Pt), whereas the reaction of 1 with [Ru(η 6- p -cymene)Cl 2 ] 2 and [AuCl(SMe 2)] yielded the corresponding bimetallic complexes [Fe{C 5 H 4 P(C CPh) 2 } 2 {RuCl 2 (η 6- p -cymene)} 2 ] (7) and [Fe{C 5 H 4 P(C CPh) 2 } 2 {AuCl} 2 ] (15). The reactions between 1 and CuX in equimolar ratios also yielded binuclear complexes, [Fe{C 5 H 4 P(C CPh) 2 } 2 {CuX} 2 ] (11 X = Cl, 12 X = Br, 13 X = I), whereas [Cu(CH 3 CN) 4 ]BF 4 yielded the cationic complex [(Fe{C 5 H 4 P(C CPh) 2 } 2) 2 Cu]BF 4 (14). All the compounds were characterized by spectroscopic methods and the structures of complexes 1 , 5 , 6 , 8 , 10 , 13 and 14 were confirmed by single crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The synthesis of η5‐Cr(CO)3 complexed 2,5‐Fc2‐ (3a), 3,4‐Fc2‐ (3b), 2,3‐Fc2‐ (3c) and 2‐Fc‐3,4,5‐Me3‐thiophenes (3d) [Fc = Fe(η5‐C5H4)(η5‐C5H5)] is described. These half‐sandwich compounds are accessible by the reaction of Cr(CO)3(MeCN)3 with the appropriate substituted thiophenes. The compounds were analyzed by NMR spectroscopy, where a highfield shift for the ring‐carbons and substituted hydrogen atoms of the thiophene core occurred. The 2,5‐ and 3,4‐derivatives could be characterized structurally by single‐crystal X‐ray diffraction analysis, demonstrating that a low bending of the sulfur atom out of the thiophene plane of up to 9.95(17)° and an anti‐arrangement of the ferrocenyl and Cr(CO)3 fragments is characteristic. Electrochemical measurements showed that each ferrocenyl unit could be oxidized separately with higher redox separations for the ferrocenyls of Cr(CO)3 complexes 3b (372 mV) and 3c (334 mV), than for the non complexed species 1b (244 mV) and 1c (283 mV). The potentials of the oxidation processes are shifted anodically by up to 144 mV, indicating an electron‐withdrawing character of the Cr(CO)3 unit. The irreversible Cr/Cr+ oxidations occurred at 545–895 mV. Within the electrochemical studies it could be shown that upon oxidation of the ferrocenyls the Cr(CO)3 half‐sandwich compounds rapidly decompose giving their non complexed thiophenes 1a–d. Solely for the Cr(CO)3‐2,3,4,5‐Me4‐thiophene 3d a reversible redox behavior was observed. The synthesis of ferrocenyl‐substituted thiophenes bearing η5‐Cr(CO)3 fragments is reported for several substitution pattern. Molecular structures in the solid state are discussed and the electrochemical properties were investigated, whereby the Cr(CO)3 fragment is released upon oxidation, resulting in the respective starting thiophenes. [ABSTRACT FROM AUTHOR]