Search

Since its discovery in the early 1950s, the sandwich‐type structure of ferrocene has sparked significant research into its applications across various disciplines, including asymmetric synthesis, medicinal chemistry, and materials science. Planar chiral ferrocenes play a crucial role in asymmetric catalysis by serving as essential scaffolds for chiral ligands and catalysts. Classical methods for synthesizing planar chiral ferrocenes often encounter limitations such as low atom economy and lengthy synthesis steps. In contrast, catalytic desymmetrization synthesis strategies offer a promising alternative due to their ability to enhance step and atom efficiency. This review highlights recent advancements in this field, particularly focusing on transition‐metal‐catalyzed C−H functionalization and catalytic enantioselective desymmetrization reactions. [ABSTRACT FROM AUTHOR]

A biradical formed by coordination of the organogold derivative of a nitronyl nitroxide radical with 1,1′-bis(diphenylphosphino)ferrocene was obtained. According to X-ray diffraction data, the Au—Au distance in the biradical structure is short (3.372 Å). The O atoms of paramagnetic groups form short intramolecular contacts with H atoms of cyclopentadienyl anions (2.360 and 2.581 Å) and with methyl H atoms (2.280 and 2.525 Å), as well as intermolecular contacts with H atoms of methyl groups (2.462 and 2.610 Å). Using cyclic voltammetry, it was established that the oxidation of the biradical occurs reversibly in three stages at potentials equal to −34, 232, and 845 mV vs. Ag/AgCl. Density functional calculations and the QTAIM and NBO analyses revealed that there is a weak noncovalent bond between gold atoms in the biradical complex due to partial transfer of an electron from the 5d orbital of one AuI ion to the 6s orbital of the other AuI ion. A weak intramolecular antiferromagnetic exchange interaction (J/kB ≈ −20 K) in the crystal structure was predicted. [ABSTRACT FROM AUTHOR]

Herein, a new semi‐organic aqueous flow battery based on a hydroxylated tetracationic viologen, 1,1′‐bis(3‐((2‐hydroxyethyl)dimethylammonio)propyl)‐[4,4′‐bipyridine]‐1,1′‐diium tetrachloride ([(DMAE‐Pr)2‐Vi]Cl4), and the ferrocene derivative, (ferrocenylmethyl)trimethylammonium chloride (FcNCl), is demonstrated. Efficiency, accessible capacity, and capacity retention of the battery are investigated at two concentrations of the active redox species: 0.1 and 0.5 mol dm−3 in 1 mol dm−3 KCl near‐neutral electrolytes. The implementation of the ferrocene‐derivative posolyte decreases the capacity fade rate by a factor of ≈4 with respect to previous work using 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPOL) as posolyte. Capacity loss is driven by crossover of the positive redox couple into the negolyte, in particular at high concentrations, indicating the need for more selective membranes and less permeable ferrocene derivatives. Discussions are supported by conductivity measurements, cell resistance, and postmortem analysis of the electrolytes using cyclic voltammetry and nuclear magnetic resonance (NMR) spectroscopy. The characterization of [(DMAE‐Pr)2‐Vi]Cl4 is expanded as a high‐energy negolyte and future scaleup requirements for aqueous organic flow batteries are informed. [ABSTRACT FROM AUTHOR]

Herein, a new semi‐organic aqueous flow battery based on a hydroxylated tetracationic viologen, 1,1′‐bis(3‐((2‐hydroxyethyl)dimethylammonio)propyl)‐[4,4′‐bipyridine]‐1,1′‐diium tetrachloride ([(DMAE‐Pr)2‐Vi]Cl4), and the ferrocene derivative, (ferrocenylmethyl)trimethylammonium chloride (FcNCl), is demonstrated. Efficiency, accessible capacity, and capacity retention of the battery are investigated at two concentrations of the active redox species: 0.1 and 0.5 mol dm−3 in 1 mol dm−3 KCl near‐neutral electrolytes. The implementation of the ferrocene‐derivative posolyte decreases the capacity fade rate by a factor of ≈4 with respect to previous work using 4‐hydroxy‐2,2,6,6‐tetramethylpiperidin‐1‐oxyl (TEMPOL) as posolyte. Capacity loss is driven by crossover of the positive redox couple into the negolyte, in particular at high concentrations, indicating the need for more selective membranes and less permeable ferrocene derivatives. Discussions are supported by conductivity measurements, cell resistance, and postmortem analysis of the electrolytes using cyclic voltammetry and nuclear magnetic resonance (NMR) spectroscopy. The characterization of [(DMAE‐Pr)2‐Vi]Cl4 is expanded as a high‐energy negolyte and future scaleup requirements for aqueous organic flow batteries are informed.

A direct protocol for Rh‐catalyzed C−H amidation of ferrocenes in a ball mill using dioxazolones as the amide source under solvent‐free conditions was developed. The corresponding ortho‐aminated products were formed in 3 hours and the yields were up to 99% in the absence of base. This method could be a typically sustainable and environmental‐friendly alternative method to traditional methodologies, with the advantages of wide substrate range, good functional group tolerance and gram‐scale synthesis. [ABSTRACT FROM AUTHOR]

Diol scaffolds have been utilized as highly effective catalysts and ligands in a wide range of catalytic asymmetric transformations. For scaffolds to be successful as broadly used motifs, they should be prepared cheaply through facile routes and be easily handled. Herein, the synthesis of a family of planar chiral diols based on a modular and robust three‐step route is described, which yields catalytically active diols in >99 % de and >99 % ee, with up to seven different chiral elements. These diols have been characterized by X‐ray crystallographic analysis, which provides clear evidence for the likely transition state when applied in the asymmetric hetero‐Diels‐Alder reaction. Without altering the stereochemistry of the catalyst backbone, it is possible to access both enantiomers of the product by varying the substitution of the catalyst at the α‐position. [ABSTRACT FROM AUTHOR]

An approach allowing remote editing of stacked aromatic assemblies for heteroannular C−H functionalization would represent a transformative chemical toolbox that may make the diversification of complex molecules in a straightforward manner. However, such a C−H activation is usually less kinetically and thermodynamically favorable than homoannular ortho C−H activation and remains a fundamental challenge. Herein we disclose an engineer's approach, using a transient ligand as an interim bridge between two aryl rings (analogues to mountaintops) to anchor the metal center on the remote heteroannular C−H bond. As a proof‐of‐concept, we present the palladium‐catalyzed heteroannular C−H olefination of stacked aromatic assemblies with olefins and allylation with vinyl acetates using L‐tert‐leucine acid as a transient ligand. Mechanistic investigations suggest an unusual olefin coordination‐promoted interannular palladium migration process determinative for reversal of the site‐selectivity. [ABSTRACT FROM AUTHOR]

Thioamide‐chelation‐assisted direct Rh(III)‐catalyzed C−H vinylation and Ir(III)‐catalyzed C−H arylation of ferrocenes with vinyl‐ or aryl‐trimethoxysilane under mild and base‐free conditions is described. With thioamide as directing group, various monovinyl and monoaryl substituted thioamideferrocenes were obtained by transition metal‐catalyzed direct C−H functionalization of ferrocenes in 50%‐84% yields with broad substrate range. Mechanistic experiments indicate that C−H bond activation may be the rate‐determining step of the reaction. [ABSTRACT FROM AUTHOR]

The results of cyclic, differential pulse and square wave voltammetric studies of four ferrocene derivatives, i.e., 4-ferrocenyl-3-methyl aniline (FMA), 3-Chloro-4-ferrocenyl aniline (CFA), 4-ferrocenyl aniline (FA) and ferrocenyl benzoic acid (FBA) on carbon electrode, revealed that the redox behavior of these compounds is sensitive to pH, concentration, scan number and scan rate. One electron, diffusion controlled, with a quasi-reversible redox signal displaying ferrocene/ferrocenium couple was observed for each of the studied ferrocenyl derivatives. Quasi-reversibility of this signal is evidenced by ∆Ep, Ia/Ic current ratio and ksh values. Another one electron and one proton irreversible oxidation signal was noticed in the voltammograms of these compounds except FBA. This signal corresponds to the electro-oxidation of the amine group and its irreversibility, as supported by ∆Ep, Ia/Ic current ratio and ksh values, is due to the influence of the electron donating nature of the amine group. A number of electrochemical parameters such as D, ksh, LOD and LOQ were evaluated for the targeted ferrocene derivatives. The obtained parameters are expected to provide insights into the redox mechanism for understanding their biochemical actions. The electrochemistry presented in this work is done using a unique environmentally benign and cost-effective droplet electrochemical approach. [ABSTRACT FROM AUTHOR]

Enantiopure propargylic amines are highly valuable synthetic building blocks. Much effort has been devoted to develop methods for their preparation. The arguably most important strategy is the 1,2‐addition of alkynes to imines. Despite remarkable progress, the known methods using Zn and Cu catalysts suffer from the need for high catalyst loadings, typically ranging from 2–60 mol % for neutral aldimine substrates. Here we report a planar chiral Pd complex acting as very efficient catalyst for direct asymmetric alkyne additions to imines, requiring very low catalyst loadings. Turnover numbers of up to 8700 were accomplished. Our investigation suggests that a Pd‐acetylide complex is generated as a catalytically relevant intermediate by the aid of an acac ligand acting as internal catalytic base. It is shown that the catalyst is quite stable under the reaction conditions and that product inhibition is not an issue. A total of 39 examples is shown which all yielded almost enantiopure products. [ABSTRACT FROM AUTHOR]

Multiple synthetic pathways were explored for the preparation of ethynylarene‐containing ferrocenylene macrocyles. Accordingly, the synthesis of novel bis‐ and tris‐ferrocenylene macrocycles, containing a diethynylpyridine bridging group was achieved, and evidence is also provided for a number of linear‐analogues formed as by‐products. The electrochemical properties of the macrocycles were examined, and it was shown that the number of observable redox processes does not necessarily correlate with the number of redox active centres. Additionally, examination of the comproportionation constants of the tris‐ferrocenylene macrocycle demonstrated that the monocationic and dicationic species could be assigned to class II and I/II borderline of the Robin‐Day classification, respectively. The synthesis of these molecules presents an opportunity towards the development of conjugated ferrocenylene macrocycles for electronic applications. [ABSTRACT FROM AUTHOR]

Reductive aminations of ferrocenecarboxaldehyde, ansa‐ferrocenecarboxaldehyde, and 1,1′‐ferrocene‐dicarboxaldehyde with allylamine, N‐allylmethylamine, or N‐allylaniline were investigated. In the case of the dialdehyde only one formyl group effectively reacted with N‐allylmethylamine or N‐allylaniline, thus providing a simple route to aminomethyl aldehydes and aminomethyl alcohol. 2‐Aza‐ansa[3] ferrocene was also obtained by reacting the dialdehyde with one equivalent of allylamine and subsequent deprotection of the nitrogen atom. The isolated N‐allyl ferrocene derivatives were completely characterized by spectroscopic techniques, whereas crystal structures of four representative compounds were determined using single‐crystal X‐ray diffraction. MTT assays showed that these simple N‐allyl ferrocene derivatives display anticancer activity (MCF‐7, A‐549 and PC‐3 cell lines) in the micromolar range. [ABSTRACT FROM AUTHOR]

Planar chiral ferrocenes are well‐known compounds that have attracted interest for application in synthesis, catalysis, material science, and medicinal chemistry for several decades. In spite of the fact that asymmetric synthesis procedures for obtaining enantiomerically enriched ferrocenes are available, sometimes, the accessible enantiomeric excess of the chiral products is unsatisfactory. In such cases and for resolution of racemic planar chiral ferrocenes, enantioselective high‐performance liquid chromatography (HPLC) on polysaccharide‐based chiral stationary phases (CSPs) has been used in quite a few literature articles. However, although moderate/high enantioselectivities have been obtained for planar chiral ferrocenes bearing polar substituents, the enantioseparation of derivatives containing halogens, or exclusively alkyl groups, remains rather challenging. In this study, the enantioseparation of ten planar chiral 1,2‐ and 1,3‐disubstituted ferrocenes was explored by using five polysaccharide‐based CSPs under multimodal elution conditions. Baseline enantioseparations were achieved for nine analytes with separation factors (α) ranging from 1.20 to 2.92. The presence of π‐extended systems in the analyte structure was shown to impact affinity of the most retained enantiomer toward amylose‐based selectors, observing retention times higher than 80 min with methanol‐containing mobile phases (MPs). Electrostatic potential (V) analysis and molecular dynamics (MD) simulations were used in order to study interaction modes at the molecular level. [ABSTRACT FROM AUTHOR]

Ferrocene‐1,1′‐dithiol reacts with PCl3 and P(NMe2)3 to give [3]ferrocenophanes with SPS‐ansa‐bridges comprising potentially reactive P−Cl and P−N bonds at the central bridge atom. The products were characterized by NMR data and single‐crystal XRD studies. The P‐chloro‐derivative exists both in the solid state and in solution as a mixture of two energetically nearly degenerate conformers with different stereochemical disposition of the ansa‐bridge. Activation parameters for the dynamic equilibration between both isomers in solution were determined by dynamic NMR spectroscopy. Computational studies suggest that the isomerization proceeds via a torsional motion of the bridging SPS‐unit rather than via configuration inversion at the phosphorus atom. [ABSTRACT FROM AUTHOR]

In this work, the synthesis and characterization of a compact, ferrocene tetramer and a linear viologen polymer is reported. The latter material is a new, 4,4′‐bipyridine containing, organo‐soluble polymer. As aimed for solubility in nonpolar solvents, a 2‐ethylhexyl‐moiety to promote organosolubility and 4‐vinylbenzyl serving as a polymerizable group are introduced to a 4,4′‐bipyridine. The halide anions of the monomer cation are exchanged to bis(trifluoromethansulfon)imide, which further enhances organosolubility. The monomer is subsequently copolymerized with styrene by free radical polymerization. In addition, a four‐ferrocene‐containing compact structure, based on pentaerythritol, is synthesized via the straightforward radical thiol‐ene reaction. The polymer solutions are thoroughly characterized hydrodynamically. Subsequently, propylene carbonate‐based solutions of both materials are prepared to allow an assessment for future energy storage applications. This is done by testing battery characteristics in a custom‐made flow‐cell with a simple dialysis membrane for physical separation of the active materials. The capability of energy storage is verified by leaving the charged materials in solution in an open circuit for 24 h. Here, more than 99% of the stored charges can be recovered. Cycling the battery for 100 times reveals the remarkable stability of the materials of only 0.2% capacity loss per day in the battery setup. [ABSTRACT FROM AUTHOR]

The results of cyclic, differential pulse and square wave voltammetric studies of four ferrocene derivatives, i.e., 4-ferrocenyl-3-methyl aniline (FMA), 3-Chloro-4-ferrocenyl aniline (CFA), 4-ferrocenyl aniline (FA) and ferrocenyl benzoic acid (FBA) on carbon electrode, revealed that the redox behavior of these compounds is sensitive to pH, concentration, scan number and scan rate. One electron, diffusion controlled, with a quasi-reversible redox signal displaying ferrocene/ferrocenium couple was observed for each of the studied ferrocenyl derivatives. Quasi-reversibility of this signal is evidenced by ∆Ep, Ia/Ic current ratio and ksh values. Another one electron and one proton irreversible oxidation signal was noticed in the voltammograms of these compounds except FBA. This signal corresponds to the electro-oxidation of the amine group and its irreversibility, as supported by ∆Ep, Ia/Ic current ratio and ksh values, is due to the influence of the electron donating nature of the amine group. A number of electrochemical parameters such as D, ksh, LOD and LOQ were evaluated for the targeted ferrocene derivatives. The obtained parameters are expected to provide insights into the redox mechanism for understanding their biochemical actions. The electrochemistry presented in this work is done using a unique environmentally benign and cost-effective droplet electrochemical approach.

1,2,3-triazoles, the corresponding triazolium salts, and the resulting mesoionic carbenes (MICs) of the 1,2,3-triazol-5- ylidene type are at the forefront of contemporary research. In this contribution, we present a comprehensive study involving eight triazoles, seventeen triazolium salts, two silver(i)- and four gold(i)-MIC complexes. The substituents on the N1-atom of the heterocycles are either ferrocenyl or phenyl and those on the C4-atom bear various alkyl groups. All the compounds were thoroughly characterized by a combination of multinuclear NMR spectroscopy, ESI-MS and in many cases through single crystal X-ray diffraction studies. In the electrochemical analysis, all ferrocenyl-containing compounds display a ferrocenyl-based oxidation step. Additionally, in both the triazolium salts, and the respective metal complexes, a ligand centered reduction step is observed. All the complexes were tested for their antibacterial properties against the Gram-negative bacterial strains Salmonella typhimurium (S. typhimurium) and Escherichia coli (E. coli). Many of the tested compounds display good antibacterial activity against the rather resistant Salmonella strain. To inhibit the growth of E. coli, higher concentrations of the compounds tested were required. A preliminary structure-activity relationship of this set of compounds is also reported. [ABSTRACT FROM AUTHOR]

Two rare-earth (La and Lu) naphthalene complexes supported by a ferrocene diamide ligand activate P4 under ambient conditions to form M 3P7 species exclusively. The resulting complexes feature a Zintl-type polyphosphide P73- unit stabilized by three lanthanide fragments. The reported metal complexes were characterized by X-ray crystallography, multinuclear NMR spectroscopy, and elemental analysis. © 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

tert‐Butyl‐substituted diphospha[2]ferrocenophane has been used as a stereochemically confined diphosphane to explore the addition of O, S, Se and Te. Although the diphosphanylchalcogane has been obtained for tellurium, all other chalcogens give diphosphane monochalcogenides. The latter transform via chalcogen‐transfer rearrangement to the corresponding diphosphanylchalcoganes upon heating. The kinetics of this rearrangement has been followed with NMR spectroscopy supported by DFT calculations. Intermediates during rearrangement point to a disproportionation/synproportionation mechanism for the S and Se derivatives. Cyclic voltammetry together with DFT studies indicate ferrocene‐centred oxidation for most of the compounds presented. [ABSTRACT FROM AUTHOR]

The concept of "flexible steric bulk" is discussed at 2‐phenylvinyl‐1‐phosphinoferrocenes. The introduction of freely rotatable 1'‐silyl groups increases the catalytic productivity within the synthesis of tri‐ortho‐substituted biaryls by Suzuki–Miyaura C,C cross‐coupling reactions, giving higher yields with 1/4 of catalyst concentration than for the non‐silylated derivatives. Electronic modification of the P and the vinyl donor functionalities was investigated by introducing substituents in the para positions of both groups. Therein, electron‐withdrawing phosphines increased the yield from 78 to 91 % for a given biaryl, by changing from a diphenylphosphino to the P(p‐CN‐C6H4)2 unit. Opposite results, obtained from electron‐donating and sterically demanding phosphines, were in accordance with the 1J(31P,77Se) values. However, the electron density of the ferrocenyl backbone, expressed by the redox potential of the first ferrocenyl‐related redox process, cannot be correlated with the donor‐properties at the P atom. Changing from a PPh2‐substituted ferrocene to a (RA)‐1,1'‐binaphthyl‐containing phosphonite, a complex interaction between the axial‐ and the planar‐chiral motifs occurs, resulting a change of the absolute biaryl configuration. [ABSTRACT FROM AUTHOR]

As redox‐active based supercapacitors are known as highly desirable next‐generation supercapacitor electrodes, the targeted design of two ferrocene‐functionalized (Fc(COOH)2) clusters based on coinage metals, [(PPh3)2AgO2CFcCO2Ag(PPh3)2]2⋅7 CH3OH (SC1: super capacitor) and [(PPh3)3CuO2CFcCO2Cu(PPh3)3]⋅3 CH3OH (SC2), is reported. Both structures are fully characterized by various techniques. The structures are utilized as energy storage electrode materials, giving 130 F g−1 and 210 F g−1 specific capacitance at 1.5 A g−1 in Na2SO4 electrolyte, respectively. The obtained results show that the presence of CuI instead of AgI improves the supercapacitive performance of the cluster. Further, to improve the conductivity, the PSC2 ([(PPh3)2CuO2CFcCO2]∞), a polymeric structure of SC2, was synthesized and used as an energy storage electrode. PSC2 displays high conductivity and gives 455 F g−1 capacitance at 3 A g−1. The PSC2 as a supercapacitor electrode presents a high power density (2416 W kg−1), high energy density (161 Wh kg−1), and long cycle life over 4000 cycles (93 %). These results could lead to the amplification of high‐performance supercapacitors in new areas to develop real applications and stimulate the use of the targeted design of coordination polymers without hybridization or compositions with additive materials. [ABSTRACT FROM AUTHOR]

Twofold C−H annulation of readily available formamides and alkynes without built‐in chelating groups was achieved. Ni−Al bimetallic catalysis enabled by a bulky BINOL‐derived chiral secondary phosphine oxide (SPO) ligand proved to be critical for high reactivity and high selectivity. This reaction uses readily available formamides as starting materials and provides a concise synthetic pathway to a broad range of chiral ferrocenes in 40–98 % yield and 93–99 % ee. [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]

Two isomeric phenyl‐bridged ferrocenyl and ruthenium alkynyl complexes 1 and 2 are synthesized and characterized through NMR, elemental analysis, and X‐ray single‐crystal diffraction. The electronic properties of the complexes are investigated via electrochemical studies, UV/Vis‐NIR and IR spectroelectrochemistry, and theoretical calculations. Cyclic voltammetry and square‐wave voltammetry technologies show two successive redox behaviors from Ru(II) and ferrocenyl centers in 1 and 2, respectively. These behaviors are supported by the dominant spin–spin density distribution in RuCp*(dppe) terminals. The large potential difference (ΔE1/2) and comproportionation constants (Kc) observed in complex 1 suggest that 1+ has better chemical stability than 2+. Strong electronic communication from 1+ are detected through the observed NIR absorption band in 1+ and large Δν(C≡C) value of 1→1+. The broad NIR absorption in 1+ is reproduced and assigned to ferrocenyl to the Ru(III) center charge transfer transition with major contributions from the β‐HOSO→β‐LUSO transition. [ABSTRACT FROM AUTHOR]

The vibronic properties of two dimeric iron (II) high-spin complexes [5CpFeX]2 (5Cp = Pentaisopropyl-cyclopentadienyl, X = OH-(1), Br-(2)) have been studied using nuclear inelastic scattering (NIS). In order to assign the experimentally observed bands to the particular modes, theoretical calculations using density functional theory (DFT) have been performed based on the structural data obtained by X-ray crystallography. The calculated partial density of vibrational states (pDOS) reproduces the experimental data. Thus, we were able to assign almost each of the experimentally observed NIS bands to their corresponding molecular vibrational modes. [ABSTRACT FROM AUTHOR]

Three sets of 7‐deazaadenine and cytosine nucleosides and nucleoside triphosphates bearing either unsubstituted ferrocene, octamethylferrocene and ferrocenecarboxamide linked through an alkyne tether to position 7 or 5, respectively, were designed and synthesized. The modified dNFcXTPs were good substrates for KOD XL DNA polymerase in primer extension and were used for enzymatic synthesis of redox‐labelled DNA probes. Square‐wave voltammetry showed that the octamethylferrocene oxidation potential was shifted to lower values, whilst the ferrocenecarboxamide was shifted to higher potentials, as compared to ferrocene. Tailed PEX products containing different ratios of Fc‐labelled A (dAFc) and FcPa‐labelled C (dCFcPa) were synthesized and hybridized with capture oligonucleotides immobilized on gold electrodes to study the electrochemistry of the redox‐labelled DNA. Clearly distinguishable, fully orthogonal and ratiometric peaks were observed for the dAFc and dCFcPa bases in DNA, demonstrating their potential for use in redox coding of nucleobases and for the direct electrochemical measurement of the relative ratio of nucleobases in an unknown sequence of DNA. [ABSTRACT FROM AUTHOR]

Here, we present an evaluation of two new monosubstituted ferrocene (Fc) derivatives, 3-(1H-pyrrol-1-yl)propanamidoferrocene and 1-hydroxy-2-[2-(thiophen-3-yl)-ethylamino]ethylferrocene, as glutamate oxidase mediators, together with their preparation and characterisation. Taking into consideration the influence of the electronic effects of substituents on the redox potentials of the Fc species, two candidates with pyrrole or thiophene moieties were proposed for investigation. Film studies involved potential sweeping in the presence of pyrrole or 3,4-ethylenedioxythiophene monomers resulting in stable electroactive films with % signal loss upon cycling ranging from 1 to 7.82% and surface coverage (Γ) 0.47–1.15 × 10−9 mol/cm2 for films formed under optimal conditions. Construction of a glutamate oxidase modified electrode resulted in second-generation biosensing with the aid of both cyclic voltammetry and hydrodynamic amperometry, resulting in glutamate sensitivity of 0.86–1.28 μA/mM and Km (app) values over the range 3.67–5.01 mM. A follow-up enzyme assay for liver biomarker γ-glutamyl transpeptidase realised unmediated and mediated measurement establishing reaction and incubation time investigations and a realising response over γ-glutamyl transpeptidase with a sensitivity of 5 nA/UL−1.

The new asymmetric click CuAAC reaction is used for the first time to induce asymmetry in planar chiral compounds. There are only three classes of stereogenicity (atom‐centred, axial and planar), and these results are therefore of fundamental importance as well as practical significance, providing access to chiral ferrocenes at near enantiopurity. Here, we report asymmetric induction (AI) and kinetic resolution (KR) studies on a novel library of prochiral 1,2,3‐trisubstituted bis‐alkynylferrocenes, obtained by diiodination, derivatisation (including reduction and etherification), double Sonogashira coupling and finally transesterification, azidation or silylation. Desymmetrisation using chiral ligands to modify the CuAAC reaction proceeds in up to 60 % yield and >99.5 % ee, yielding planar chiral ferrocenes. The absolute configuration of two of the preferred products was proved by chemical correlation and related to the entire series by circular dichroism spectroscopy (CD). [ABSTRACT FROM AUTHOR]

The present study refers to the chemical doping of ferrocene materials from the reaction with 2,6-Dihydroxyanthraquinone and 2,6-Diaminoanthraquinone. Thin films of the doped molecular materials were prepared by vacuum evaporation and the morphology and structure of films were studied using SEM, EDS and IR spectroscopy. Theoretical calculations were carried out by means Gaussian16 software and all the involved species were geometrically optimized. The IR spectrum, the HOMO-LUMO energy and the bandgaps from these calculations were achieved. The theoretical and experimental IR spectra were compared in order to verify the presence of the main functional groups of the molecular materials. The theoretical bandgap of each film was also compared with that obtained by UV–vis spectroscopy, showing similar results in the range of 2–2.9 eV. These bandgap values place the synthesized materials within the so-called organic semiconductors. Additionally from the calculations of HOMO-LUMO and bandgap results, it has been suggested that the synthesized materials can be used as a semiconductor p-type. The films were evaluated in their p -type semiconductor behavior by means of unipolar devices. In the material synthesized from ferrocene and 2,6-Dihydroxyanthraquinone a virtually ohmic I-V ratio was obtained, while the compound constituted by 2,6-Diaminoanthraquinone behaved as an insulator. In order to improve the p -type behavior of the synthesized semiconductors, unipolar devices were given a hole-injecting layer between the anode and the synthesized materials: glass/ITO/CuPc/synthesized material/Ag. Its I-V electrical behavior was evaluated by the effect of influencing electromagnetic radiation in the range of the electromagnetic spectrum between the IR and the UV passing through the visible spectrum. The results for both devices have shown that the one manufactured from ferrocene and 2,6-Dihydroxyanthraquinone exhibited a behavior similar to that of a Schottky diode, while the one prepared from ferrocene and 2,6-Diaminoanthraquinone behaves like a resistor. Image 103 • Molecular materials were synthesized from ferrocene and anthraquinone derivatives. • Theoretical calculations were carried out and all the species were optimized. • Theoretical and experimental bandgap of each Fc-based material was compared. • The synthesized molecular materials could be used as a semiconductor p-type. • Unipolar devices of each Fc-based material synthesized were manufactured. [ABSTRACT FROM AUTHOR]

Abstract Functional block copolymers (BCPs) featuring metal moieties are a unique class of materials because of their switching capabilities and pronounced microphase separation behaviour. Within this work, ABC and CBABC tri- and pentablock terpolymers consisting of polystyrene (PS), poly(1,1′-dimethylsilaferrocenophane) (PFS) and a third block segment C either consisting of poly(methyl methacrylate) (PMMA) or poly(2-vinylpyridine) (P2VP) were synthesized via sequential living anionic polymerization. Well-defined polymers having molar masses up to 90 kg mol−1 and low dispersity index values, Đ , below 1.10 were obtained. The multi-functional BCPs were characterized with respect to their constitution and composition by size-exclusion chromatography (SEC) measurements and NMR spectroscopy. Focus of this work was to study the microphase separation of the metal-containing tri- and pentablock terpolymers by (scanning) transmission electron microscopy (TEM) and small-angle X-ray scattering (SAXS) measurements. Highly ordered structures at the nanoscale were observed comprising lamellar or cylindrical morphologies with more complex core-shell cylindrical morphologies for the organometallic block segment. This structure formation was more pronounced in case of P2VP-containing ABC terblock copolymers. Finally, synthetic approaches for the preparation of CBABC pentablock terpolymers were presented and the obtained bulk morphologies of these polymers were investigated by TEM and SAXS measurements. Graphical abstract Image 1 Highlights • Synthetic approach for ABC and CBABC metallopolymers. • Self-assembly and tailored block copolymer morphologies. • Structure elucidation by transmission electron microscopy and small-angle X-ray scattering. • Preparation and morphological studies by SEM and EDX. • Well-defined block copolymers by sequential anionic polymerization. [ABSTRACT FROM AUTHOR]

Abstract A series of ferrocenes which contain dinitrogen-fused pyrazolidinone ring were synthesized from acryloylferrocene (4) and N , N ′‑cyclic azomethine imines (3). Novel 5‑aryl‑6‑ferrocenoyltetrahydropyrazolo[1,2‑ a ]pyrazol‑1(5 H)-ones were obtained as mixtures of two diastereoisomers (trans and cis) which were separated and isolated as pure substances. Ortho -substituted N , N ′‑cyclic azomethine imines 5-oxo-2-(2,4,6-trimethylbenzylidene)pyrazolidin-2-ium-1-ide (3e) and 2-(2-methoxybenzylidene)-5-oxopyrazolidin-2-ium-1-ide (3f) reacted stereoselectively affording only trans -6-ferrocenoyl-5-mesityltetrahydropyrazolo[1,2- a ]pyrazol-1(5 H)-one (5e) and 6-ferrocenoyl-5-(2-methoxyphenyl)tetrahydropyrazolo[1,2- a ]pyrazol-1(5 H)-one (5f). Ferrocenyl derivatives were screened for in vitro antioxidant and antifungal activities and excellent DPPH and ABTS radicals scavenging activity was observed with majority of tested 5‑aryl‑6‑ferrocenoyltetrahydropyrazolo[1,2‑ a ]pyrazol‑1(5 H)-ones. Several tested compounds showed selective scavenging properties neutralizing ABTS•+ radical cations in contrast to inactivity toward DPPH radicals. Trans -5-aryl-6-ferrocenoyltetrahydropyrazolo[1,2- a ]pyrazol-1(5 H)-ones 5b , 5c , 5d , 5j as well as cis - 6 - ferrocenoyl - 5 - (p - tolyl)tetrahydropyrazolo[1,2- a ]pyrazol-1(5 H) - one (6d) displayed fungal growth inhibition at low concentration against C. albicans and/or A. brasiliensis. Molecular docking studies revealed that the cis -6-ferrocenoyl-5-(4-nitrophenyl)tetrahydropyrazolo[1,2- a ]pyrazol-1(5 H)-one (6l) and cis -6-ferrocenoyl-5-(naphthalen-2-yl)tetrahydropyrazolo[1,2- a ]pyrazol-1(5 H)-one (6n) have potential to become lead molecules in drug discovery process. Graphical abstract A series of new ferrocenes (5‑aryl‑6‑ferrocenoyltetrahydropyrazolo[1,2‑ a ]pyrazol‑1(5 H)-ones) is characterized in a terms of examination of their biological activities. Synthesized compounds exhibited excellent antioxidant properties, and in some cases antibacterial and antifungal activity. Unlabelled Image Highlights • A series of new ferrocenes is synthesized using easy performable procedure. • The isolated pure ferrocenes showed pronounced antioxidant activity. • The tested compounds exhibited different and selective antimicrobial activity. [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.

Bis(ferrocenyl)‐appended dioxido molybdenum(VI) complexes perform oxygen‐atom transfer (OAT) reactions similar to sulfite oxidases. Positively charged ferrocenium ions accelerate the nucleophilic attack of the substrate. The fate of the intermediate species formed after the OAT depends on the initial redox states of the iron centers. In the all‐iron(II) state of the ferrocenyl moieties, a simple OAT from the FeIIFeIIMoVIO2 unit to a PMe3 substrate occurs yielding FeIIFeIIMoIVO and OPMe3 without participation of the iron(II) centers. In the all‐iron(III) state, the ferrocenium intermediates are susceptible to decomposition initiated by the nucleophilic substrate. However, in the mixed FeII/FeIII state, OAT to PMe3 is rapidly followed by an intramolecular electron transfer (IET) within the initially formed FeIIFeIIIMoIVO(OPMe3) species to give the FeIIFeIIMoVO(OPMe3) electromer. The absence of ferrocenium species, the presence of molybdenum(V) and the coordinated OPMe3 in the quite persistent FeIIFeIIMoVO(OPMe3) electromer is demonstrated by EPR spectroscopy in combination with Density Functional Theory calculations. The IET‐coupled OAT reaction stabilizes this molybdenum(V) intermediate compared to the conventional molybdenum(IV) OAT reaction intermediate. This stabilization enables its characterization by spectroscopic means before the OPMe3 product dissociates. This study presents a concept for redox‐controlled stabilization of a catalytically relevant intermediate. [ABSTRACT FROM AUTHOR]

Abstract: Construction of biocompatible nanoparticles is a significant topic of research at the chemistry/biology interface. Presently, more and more researchers have focused on supramolecular amphiphiles constructed by macrocycle‐induced aggregation, a feasible and universal strategy in the fabrication of functional nanomaterials. In this work, we report a pH‐responsive nanoparticle through a noncovalent complexation between per‐6‐thiolated β‐cyclodextrin sodium salt (SACD) and amphiphilic ferrocene derivative (FC12+Br−) in water. The formation and composition of the obtained supramolecular nanoparticles were comprehensively characterized by UV/Vis absorption, dynamic laser scattering, and microscopic observations. Furthermore, the drug loading and release studies demonstrated that the supramolecular binary nanoparticles could efficiently encapsulate doxorubicin hydrochloride (DOX) in their nanoparticulate cores, and the entrapped DOX could be rapidly released in a low pH environment. The present study suggests that the obtained binary supramolecular amphiphiles with good stability, tunable assembling/disassembling behaviors, and controlled drug loading/release properties have great potential in the construction of on‐demand drug‐delivery systems. [ABSTRACT FROM AUTHOR]

9-Fluorenone azine 2a and benzophenone azine 2b were synthesized, respectively, by treatment of 9-fluorenone hydrazone 1a or benzophenone hydrazone 1b with FeCl 3 in chloroform. Ferrocenecarboxaldehyde 3 reacts with 1a or 1b , in ethanol, to furnish novel asymmetrical azine products 1-((ferrocenyl)methylene)-2-(9 H -fluoren-9-ylidene)hydrazine 3a or 1-((ferrocenyl)methylene)-2-(diphenylmethylene)hydrazine 3b , respectively. The compounds were characterized by IR, 1 H, 13 C and DEPT-135 NMR spectroscopy, high resolution ESI + -MS or EI, and also by single crystal X-ray diffraction analysis (in the case of 2b and 3b ). The contribution of the azine functional group ( 3a ) in the LUMO orbital was justified by observing a red shift in the MLCT upon its protonation. The antimicrobial activities of 2a , 2b , 3a and 3b were determined against some Gram-positive and Gram-negative bacteria in addition to Candida albicans and Aspergillus niger using paper disc diffusion method. Moderate antibacterial activities were found for 3a and 3b while weak activities were recorded for 2a and 2b compared to Ampicillin, positive control. No antifungal or antitumor activities were found for all the tested compounds, except 3a which showed antitumor activity. Low toxicity was recorded for 3a and 3b using Artemia salina as test organism. Hence, the prepared products 3a and 3b can be used as antimicrobial agents due to their antibacterial activities and low cell toxicity. [ABSTRACT FROM AUTHOR]

Abstract: Lochmann–Schlosser superbases are formed by mixing alkyllithium with potassium alkoxides. These reagents could prove their synthetic usefulness and reliability in many reactions over five decades. However, despite many efforts, the real source of the exceptional reactivity remained a secret. The seemingly manageable system of four components (lithium, potassium atoms, alkyl groups, and alkoxy groups) and their interaction is obscured by poor solubility and fierce reactivity. Recent progress was achieved by using neopentyllithium, leading to alkane‐soluble aggregates with varying lithium/potassium content and a flexible alkyl/alkoxy ratio. Herein, we isolated two new alkane‐soluble alkyl/alkoxy mixed aggregates, [Li4KNp2(OtBu)3] and [K4Np(OtAm)3]. The latter compound is a thermally stable three‐component potassium alkyl/alkoxy base with well‐defined stoichiometry, in contrast to lithium‐containing Lochmann–Schlosser bases with variable metal and alkyl/alkoxy content. In a simple protocol, this potassium‐base gave tetrametalated ferrocene, which was converted into 1,1′,3,3′‐ferrocenetetracarboxylic acid by reaction with CO2. A subsequent conversion into the methyl ester allowed its separation from accompanying di‐ and tri‐substituted ferrocenes. [ABSTRACT FROM AUTHOR]

Abstract: The ferrocene derivative (η5‐Cp)Fe{η5‐C5H3‐1‐(ArNCH)‐2‐(CH2NMe2)} (1; Ar=2,6‐iPr2C6H3)) reacts diastereoselectively with LiR by carbolithiation and subsequent hydrolysis to give (η5‐Cp)Fe{η5‐C5H3‐1‐(ArHNCHR)‐2‐(CH2NMe2)} (3: R=tBu; 4: R=Ph; 5: R=Me) in high yields. For R=tBu, the organolithium derivative (η5‐Cp)Fe{η5‐C5H3‐1‐(ArLiNCHR)‐2‐(CH2NMe2)} (2) was isolated. Compound 2 reacts with GeCl2⋅dioxane and SnCl2 to give the metallylene amide chlorides (η5‐Cp)Fe{η5‐C5H3‐1‐(ArMNCHtBu)‐2‐(CH2NMe2)} 6 (M=GeCl) and 7 (M=SnCl), respectively, which each contain three stereogenic centers. The potential of 7 as a ligand in transition‐metal chemistry is demonstrated by formation of its complex (η5‐Cp)Fe{η5‐C5H3‐1‐(ArMNCHtBu)‐2‐(CH2NMe2)} [9, M= Sn(Cl)W(CO)5]. Treatment of 3 with tert‐butyllithium at room temperature causes an unprecedented carbon–carbon bond cleavage whereas under kinetic control, lithiation at the Cp‐3 position takes place, which leads to the isolation of (η5‐Cp)Fe{η5‐C5H3‐1‐(ArHNCHtBu)‐2‐(CH2NMe2)‐3‐SiMe3} (10). [ABSTRACT FROM AUTHOR]

The electronic interaction between two terminal ferrocenyl units connected by the cobalt bis(dicarbollide) anion linker was investigated. The bis(ferrocenylethynyl)cobalt bis(dicarbollide) anion (3) linking the two ferrocenyl units with the cobalt bis(dicarbollide) anion was synthesized by the reaction of a zinc derivative of ethynylferrocene with the diiodocobalt bis(dicarbollide) anion using Pd0 catalyst in 75 % yield. Complex 3 was unambiguously characterized by NMR and IR spectroscopy, mass spectrometry, and single-crystal X-ray crystallography. The X-ray structure of 3 reveals that the two ferrocenyl units are perpendicular to each other with a total distance of 1.86 nm between the two Fe metal centers. The cyclic voltammogram of 3 shows a single oxidation potential corresponding to the two ferrocenyl units. Time-dependent density functional theory (TD-DFT) studies on complex 3 in tandem with UV/Vis spectroscopic analysis indicate the dominance of the dicarbollide moiety in the LUMOs, and HOMO→LUMO transitions at 435 nm illustrate the charge transfer from the two ferrocenyl units to the cobalt bis(dicarbollide) linker. [ABSTRACT FROM AUTHOR]

We developed four new ferrocene containing alkylated silane self-assembled monolayers (SAMs), and evaluated their electrical properties in a metal/SAM/metal configuration. The ferrocenyl silanes used in this work can be prepared in one to two simple chemical steps from readily available ferrocene carboxaldehyde. We found that the molecular diodes obtained from these molecules can exhibit current rectification ratios as high as 150. The ease of processing coupled with the excellent rectification behavior makes these compounds very attractive for molecular electronics applications. [ABSTRACT FROM AUTHOR]

Abstract: A palladium(II)‐catalyzed thioketone‐chelation‐assisted direct C−H arylation of ferrocenes is described. With thioketone as an efficient directing group, various monoaryl‐ and diaryl‐substituted thiocarbonylferrocenes were obtained by palladium‐catalyzed direct C−H functionalization in high yields under mild and base‐free reaction conditions. Furthermore, the arylated thiocarbonylferrocene could undergo diverse transformations. [ABSTRACT FROM AUTHOR]

Controlling helical chirality and creating protein secondary structures in cyclic/acyclic ferrocene-dipeptide bioorganometallic conjugates were achieved by adjusting the conformational flexibility of the dipeptide chains. In systems reported to date, the helical chirality of a conjugate was determined by the absolute configuration of the adjacent amino acid reside. In contrast, it was possible to induce both M- and P-helical chirality, even when the configuration of the adjacent amino acid was the same. It is particularly interesting to note that M-helical chirality was produced in a cyclic ferrocene-dipeptide conjugate composed of the l-Ala- d-Pro-cystamine- d-Pro- l-Ala dipeptide sequence ( 1), in which a type II β-turn-like secondary structure was established. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of four new CrIII- bis(alkynyl) complexes bearing the macrocyclic tetraaza ligand DMC (DMC = 5,12-dimethyl-1,4,8,11-tetraazacyclotetradecane) are reported. Complexes trans-[Cr(DMC)(C2R)2]X (R = Ph ([1]X), Fc ([2]X), X = Cl, ClO4. C2H ([3]X'); X' = ClO4, BPh4) and cis- [Cr(DMC)(C4TMS)2]Cl ([4]Cl) were studied using UV/Vis and FTIR spectroscopy, and their identities were verified with ESI-MS and elemental analysis. The three trans complexes, [1]Cl, [2](ClO4), and [3](BPh4), were structurally characterized using single-crystal X-ray diffraction, which revealed a pseudo-octahedral geometry around the Cr center with the nitrogen atoms occupying the equatorial plane and the alkynyl ligands residing in the apical positions. Spectroscopic analysis of [1]Cl, [3](BPh4) and [4]Cl shows highly structured d-d bands between 320 and 500 nm. All CrIII complexes reported herein are emissive, and detailed studies were performed for [1]Cl, [3](BPh4), and [4]Cl, yielding phosphorescence lifetimes (77 K) of 380, 358, and 160 ìs, respectively, and room temperature quantum yields of 0.01% for complex [1]Cl and 0.15% for complex [4]Cl. Voltammetric studies of complex [2](ClO4) indicate a weak but discernible coupling between two ferrocenyl groups across the C2-Cr-C2 bridge. [ABSTRACT FROM AUTHOR]

The reaction of FcCH2OH with chlorophosphates gave ferrocenyl phosphates FcCH2OP(O)(OR)2 [Fc = Fe(ç5- C5H5)(ç4-C5H4)], which readily separate into phosphate anions and ferrocenyl carbo-cations. The latter species undergoes consecutive reactions, for example, electrophilic aromatic substitutions. When nitriles, instead of alcohols, are treated with FcLi or tBuLi and chlorophosphates, chiral-pool based ferrocenylimino phosphoramidates Fc-CR=N-P(O)(OR*)2 are formed, which are promising candidates for anionic homo phospho-Fries rearrangements. Moreover, the sterically demanding chiral chlorophosphate with R* enabled oxidative couplings of the imines to form a diferrocenylazine. Similarly, the reaction of Fc-Li with 9-anthrylnitrile produced a 10-ferrocenyl-substituted product, contrary to a reaction at the C≡N functionality. A planar-chiral ortho-P(S)PH2-functionalized ferrocenylmethanol also gave carbo-cations under acidic conditions. These species can be sulfurized in a unique way giving thio ethers, whereby the in situ formed 1,2-P(S)PH2,CH2 + ferrocene cation acts as the sulfur and electron source. However, lowering the substrate concentration prevents sulfur migration, resulting in electrophilic substitution reactions with aromatic solvents. Planar-chiral ferrocenylmethyl thio or anisyl derivatives were applied as ligands in Pd-catalyzed Suzuki-Miyaura C,C cross-couplings for the atroposelective synthesis of hindered hinderedbiaryls with up to 26% ee at low catalyst loadings (1 mol-% Pd). [ABSTRACT FROM AUTHOR]

An efficient synthesis of ferrocene-containing indolizine derivatives via a copper-catalyzed one-pot three-component domino amination/alkynylative cyclization is reported. This transformation proceeds through a copper-catalyzed coupling of ferrocenylacetylenes with iminiums followed by 5- endo-dig cyclization leading to ferrocenyl-substituted indolizine derivatives in good yields. [ABSTRACT FROM AUTHOR]

The ferrocenyl analogue of clotrimazole, in which the metallocene fragment replaces one of the phenyl rings in the triphenylmethane system, and a related isomer were prepared through the direct substitution of a methoxygroup in the α-position to ferrocene with imidazole in the key step. The obtained ferrocenyl derivatives were spectroscopically characterized and in a preliminary assay for bioactivity their cell growth inhibitory activity on two different human cancer cell lines was evaluated. In comparison with the parent drug the ferrocene analogues displayed about two-fold increase of cytotoxicity on HT29 colorectal cancer cells, whereas comparable activity was displayed against MCF-7 breast cancer cell line. [ABSTRACT FROM AUTHOR]

The synthesis and sensing properties of a triferrocene-bis(iodotriazole) are described. In general, halogen-bonding (XB) receptor 3 undergoes remarkable cathodic shifts of the two redox peaks in the presence of several oxoanions. These perturbations, which are attributable to noncovalent halogen-bonding interactions, are slightly smaller than those observed for the parent hydrogen-bonding (HB) receptor 4 with the same oxoanions. [ABSTRACT FROM AUTHOR]