Synthesis and structural studies of 1,1'-bis-amino-functionalized ferrocenes, ferrocene salts, and ferrocenium salts

Having isolated and characterized a series of sodium cyclopentadienide salts, we have synthesized a number of 1,1'-bis-amino-functionalized ferrocenes, 1,1'-bis-amino-functionalized ferrocene salts, and 1,1'-bis-amino-functionalized ferrocenium salts. Among these are the first crystallographically characterized examples of cyclopentadienyl units containing (piperidin-N-ylethyl)- and (pyrid-2-ylmethyl)cyclopentadienyl side chains. In the cases of some of the ferrocenes, ferrocene salts, and ferrocenium salts, there are some interesting structural features in the solid state. These include C-H...N and C-H...pi cloud interactions as well as N-H...O and N-H...F hydrogen bonds.     

Determination of the activity of superoxide dismutase using a glassy carbon electrode modified with ferrocene imidazolium salts and hydroxy-functionalized graphene

Microchimica Acta - A glassy carbon electrode was modified with a composite consisting of ferrocene imidazolium salts and hydroxy-functionalized graphene in a Nafion matrix. The electrode is shown...     

Alkynylation of ferrocene by terminal alkynes. Part I. A simple one-step synthesis of ferrocenylacetylenes

Ferrocene reacts with terminal alkynes in the presence of copper and iron salts to give 1-ferrocenyl-2-R-alkynes (R - substituent). This direct cross-coupling of ferrocenyl and alkynyl moieties allows for the preparation of ferrocenyl substituted alkynes in one step directly from ferrocene and a terminal alkyne avoiding prior preparation of other derivatives of ferrocene. This new synthetic reaction does not require special conditions, is promoted by the action of common iron and copper salts, and tolerates the presence of functional groups in the alkyne.     

On the medicinal chemistry of ferrocene

Organometallic chemistry and biochemistry have been merged in the last two decades into a new field: bioorganometallic chemistry. This new research area was devoted to the synthesis of new organometallic compounds and their biological and medical effects against some types of diseases, such as cancer and malaria. For several years, the use of ferrocene in bioorganometallic chemistry has been growing rapidly, and several promising applications have been developed since ferrocene is a stable, nontoxic compound and has good redox properties. This review will focus on ferrocenyl compounds which have been biologically evaluated against certain diseases. This area has attracted many researchers due to the promising results of some ferrocene compounds in the medicinal applications. Copyright © 2007 John Wiley & Sons, Ltd.     

2-Silver(dimethylaminomethyl)ferrocene

Conclusions 2-Silver(dimethylaminomethyl)ferrocene was synthesized by reacting 2-lithium(dimethylaminomethyl)ferrocene with AgI and some of its properties were studied.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 2354–2355, October, 1977.     

Antineoplastic activity of polyaspartamide–ferrocene conjugates

The ferrocene/ferricenium redox system plays a significant role in biological oxidation, reduction and free-radical reactions. Of particular interest are the findings of earlier investigations which showed certain water-soluble ferricenium salts to possess appreciable antiproliferative activity against various murine tumor lines and a xenografted human colorectal adenocarcinoma. Solubility in water, a prerequisite for efficacious transport and dissipation in central circulation, was then proposed as a principal requirement for the ferrocene complex system to exert antineoplastic activity irrespective of the oxidation state in which it is administered. In order to shed more light on this question, we decided to investigate the antiproliferative properties of polymer–ferrocene conjugates containing the metal complex in the non-oxidized (ferrocene) form while fulfilling the critical requirement of water solubility. To this end, five selected, water-soluble conjugates, synthesized by reversible coupling of 4-ferrocenylbutanoic acid to variously structured polyaspartamides featuring pendant primary amino groups as coupling sites, were tested in vitro against cultured HeLa cells at concentrations up to 50 µg Fe ml⁻¹. Optimal antiproliferative activities, with IC₅₀ in the range of 2–7 µg Fe ml⁻¹, were determined for three compounds possessing tertiary-amine functions susceptible to protonation at physiological pH. Lower activities (IC₅₀ = 45–60 µg Fe ml⁻¹) were demonstrated for two poly(ethylene oxide)-containing conjugates. However, no reasonable structure–performance relationships can be derived at this stage from the small number of compounds tested. Copyright © 1998 John Wiley & Sons, Ltd.     

Electron density distribution in ferrocene analogues of stilbene. Interaction of substituents and molecular groups in ferrocene derivatives

Two techniques, ¹³C NMR and cyclic voltammetry, are utilized to determine the change of electron density distribution caused by substituents in ferrocene analogues of stilbene. The interactions of substituents and some molecular groups in four series of ferrocene derivatives is discussed and the transmission coefficients of these groups are presented.     

Carboxylate anions binding and sensing by a novel tetraazamacrocycle containing ferrocene as receptor

A tetraazamacrocycle containing ferrocene moieties has been synthesized and characterized. The tetraprotonated form of this compound was evaluated as a receptor (R) for anion recognition of several substrates (S), Cl(-), PF(6)(-), HSO(4)(-), H(2)PO(4)(-) and carboxylates, such as p-nitrobenzoate (p-nbz(-)), phthalate (ph(2-)), isophthalate (iph(2-)) and dipicolinate (dipic(2-)). (1)H NMR titrations in CD(3)OD indicated that this receptor is not suitable for recognizing HSO(4)(-) and H(2)PO(4)(-), but weakly binds p-nbz(-), and strongly interacts with ph(2-), dipic(2-), and iph(2-) anions forming 1 : 2 assembled species. The largest beta(2) binding constant was determined for ph(2-), followed by dipic(2-) and finally iph(2-). The effect of the anionic substrates on the electron-transfer process of the ferrocene units of R was evaluated using cyclic voltammetry (CV) and square wave voltammetry (SWV) in methanol solution and 0.1 mol dm(-3)(CH(3))(4)NCl as the supporting electrolyte. Titrations of the receptor were undertaken by addition of anion solutions in their tetrabutylammonium or tetramethylammonium forms. The protonated ligand exhibits a reversible voltammogram, which shifts cathodically in the presence of the substrates. The data revealed kinetic constraints in the formation of the receptor/substrate entity for dipic(2-), ph(2-) and iph(2-) anions, but not for p-nbz(-). In spite of the slow kinetics of assembled species formation with the ph(2-) substrate, this anion provides the largest redox-response when the supramolecular entity is formed, followed by dipic(2-), iph(2-) and finally p-nbz(-) anions. This trend is in agreement with the (1)H NMR results and the values of the binding constants. Single crystal X-ray structures of the receptor with PF(6)(-), ph(2-), iph(2-) and p-nbz(-) were carried out and showed that supermolecules with a RS(2) stoichiometry are formed with the first three anions, but RS(4) with p-nbz(-). In all cases the binding occurs outside the macrocyclic cavity via N-H...O=C hydrogen bonds for carboxylate anions and N-H...F hydrogen bonds for the PF(6)(-) anion, which is in agreement with the solution results. The macrocyclic framework adopts different conformations in order to interact with each substrate having Fe...Fe intramolecular distances ranging from 10.125(14) to 12.783(15)A.     

Vapor pressure measurements of ferrocene,mono- and 1,1′-di-acetyl ferrocene

By using different techniques the vapor pressure of ferrocene, mono-acetyl ferrocene and 1,1′-di-acetyl ferrocene was measured. The following pressure—temperature equations were derived ferrocene log P(kPa)= 9.78 ± 0.14 ? (3805 ± 46)/T mono-acetyl ferrocene log P(kPa) = 14.83 ± 0.14 ? (5916 ± 48)/T 1,1′-di-acetyl ferrocene log P(kPa) = 8.82 ± 0.11 ? (4289 ± 44)/T By second- and third-law treatment of the vapor data the ΔH⁰_sub,298 = 74.0 ± 2.0 kJ mole^?1 for the sublimation process of ferrocene was calculated and compared with the literature data. For the sublimation enthalpy of mono- and 1,1′-di-acetyl ferrocene the values ΔH⁰_sub,298 = 115.6 ± 2.5 kJ mole^?1 and ΔH⁰_sub,298 = 91.9 ± 2.5 kJ mole^?1 were derived by second-law treatment. Thermal functions of these compounds were also estimated.     

Synthesis of ferrocene paracyclophanes

Paracyclophanes containing one or two ferrocene units can be efficiently synthesized directly from 1,1′-di(hydroxymethyl)ferrocene and aromatic dithiols. In the reaction with di(4,4′-dimercaptomethylphenyl)methane the mononuclear paracyclophane was formed, while with the dithiophenols di(4,4′-dimercaptophenyl)methane and di(4,4′-dimercaptophenyl)ether, cyclophanes bearing two ferrocene units were obtained. For comparison three open-chain analogues were also prepared.     

Chiral ferrocene cyanohydrin derivatives—access to novel intermolecularly linked and intramolecularly bridged ferrocene derivatives

By reduction of the cyano group in (R)-(cyanohydroxymethyl)ferrocene and (R,R)-1,1′-bis(cyanohydroxymethyl)ferrocene, amines were obtained giving access to several new diamine and diamide bridged chiral ferrocene derivatives. As a representative for an intramolecularly bridged ferrocene compound bearing two chiral centres (R,R)-8 was obtained with excellent optical purity.     

Application of ferrocenylimidazolium salts as catalysts for the transfer hydrogenation of ketones

Ferrocenylimidazolium salts with methylene and phenyl groups bridging the ferrocenyl and alkylimidazolium moieties were synthesized and characterized by spectroscopic and analytical methods. Crystal structures of two new compounds are also reported. Cyclic voltammetry was used to analyze the influence of the two bridging groups or spacers on electrochemical properties of the salts relative to the shifts in the formal electrode or peak potentials (E⁰ or E_1/2) of the ferrocene/ferrocenium redox couple. Results from this study showed that all the salts exhibited higher electrode potentials relative to ferrocene, which is due to the electron‐withdrawing effect of the imidazolium ion on the ferrocenyl moiety. Application of the salts as catalysts in transfer hydrogenation of ketones resulted in high conversion of saturated ketones to corresponding alcohols and turnover numbers as high as 1880. The catalysts were chemoselective towards reduction of the C═C bonds of conjugated 3‐penten‐2‐one and 4‐hexen‐3‐one to yield saturated ketones, while unconjugated 5‐hexen‐2‐one was hydrogenated to an unsaturated alcohol. Copyright © 2012 John Wiley & Sons, Ltd.     

Probing C-H...X hydrogen bonds in amide-functionalized imidazolium salts under high pressure

We have probed under high pressure the C-H hydrogen bonds formed by N,N(')-disubstituted imidazolium ions having PF(6) (-) and Br(-) counterions. High-pressure infrared spectral profiles, x-ray crystallographic analysis, and ab initio calculations allow us to make a vibrational assignment of these compounds. The appearance of a signal for the free-NH unit (or weakly bonded N-H...F unit) in the infrared spectrum of the PF(6) (-) salt indicates that conventional N-H...O and N-H...N hydrogen bonds do not fully dominate the packing. It is likely that the charge-enhanced C(2)-H...F interactions, combined with other weak hydrogen bonds, disturb the formation of N-H hydrogen bonds in the PF(6) (-) salt. This finding is consistent with the pressure-dependent results, which reveal that the C(2)-H...F interaction is enhanced upon increasing the pressure. In contrast to the PF(6) (-) salt, the imidazolium C-H bonds of the Br(-) salt have low sensitivity to high pressure. This finding suggests that the hydrogen bonding patterns are determined by the relative hydrogen bond acceptor strengths of the Br(-) and PF(6) (-) ions.     

Free-radical polymerization of vinyl ferrocene

The results of quantitative studies of the rates of free-radical polymerization of vinyl ferrocene indicate that the latter has polymerization characteristics similar to those of styrene. The rates of homopolymerization of these two monomers in benzene at 70°C. were measured with the use of azobisisobutyronitrile as catalyst. The rate constants (k = R_p/[M][I]^1/2) are k_VF = (1.1 ? 1.8) × 10^?4, k_STY = 1.65 × 10^?4. Small amounts of vinyl ferrocene and styrene have similar effects on the rates of polymerizations of methyl methacrylate and ethyl acrylate and on the molecular weights of the resulting polymer. Polystyrene and poly(vinyl ferrocene) with similar molecular weights are isolated from polymerizations carried out under identical conditions. The rates of copolymerization of vinyl ferrocene—methyl methacrylate, vinyl ferrocene—styrene, and styrene—methyl methacrylate were determined by following the disappearance of monomers by means of gas chromatographic analyses. The relative reactivity for vinyl ferrocene is slightly lower than that for styrene.     

Antitumor activities of ferrocene compounds

Data on the antitumor activities of ferrocene compounds and the results concerning the mechanisms of their action published between 1995 and 2010 are discussed. The biomedical aspects of the study of ferrocene derivatives are briefly analyzed.     

Effect of ferrocene on the synthesis of graft copolymers of vinylpolysiloxane and styrene

Russian Journal of General Chemistry - The effect of ferrocene on the synthesis of graft poly(dimethylsiloxanes) by radical copolymerization of a polysiloxane containing terminal trivinylsiloxy...     

Synthesis and un-isotherm kinetic study of some ferrocene acids

The goal of this paper is to study thermal stability of some ferrocenes with acidic functional groups. Some other kinetic characteristics such as critical temperature and the rate constant corresponding to maximal degradation speed have been also evaluated. The type of functional units adjacent to the ferrocenyl unit determines thermal stability of ferrocene compounds. Groups with a powerful withdrawing effect determine a decreasing of the temperatures at which the material starts to lose weight. If a very long alkyl chain is connected to the ferrocene unit, a shielding effect in respect to the other carboxylic groups was observed, with an increase of the thermal stability.     

Lithium redox-responsive ferrocene bis-tertiary amide derivatives

The addition of Li⁺ to ferrocene bis-tertiary amide derivatives in acetonitrile results in a shift of the ferrocene oxidation wave to more positive potentials and the appearance of a new redox couple associated with a Li⁺ complex.     

Thermodynamic properties of ferrocene dicarboxylic acid

The temperature dependence of the heat capacity of crystal ferrocene dicarboxylic acid is studied in a precision adiabatic vacuum calorimeter in the range of 8 to 350 K. Its standard thermodynamic functions are calculated in the range of T → 0 to 350 K. The thermal and physical heat properties of ferrocene dicarboxylic acid are studied on a differential scanning calorimeter in the range of 260 to 573 K. The enthalpy of combustion for the investigated compound is measured in an isoperibol calorimeter. The standard thermodynamic functions of the formation of ferrocene dicarboxylic acid in the crystal state at 298.15 K are calculated.     

On the mechanism of ferrocene oxidation under the conditions of electrospray ionization

Russian Chemical Bulletin - The formation of molecular ions of ferrocene is detected under the «inverse» conditions of electrospray ionization where the pure solvent alone is...