Ferrocenyl Units Research Articles

Electrocatalytic oxidation of dopamine on the surface of ferrocene grafted hydroxyl terminated polybutadiene modified electrode

In this study, 4-(dimethylsilyl)butylferrocene was prepared using 4-chlorobutylferrocene via Grignard reaction in dry THF and the reaction of prepared reagent with chlorodimethylsilane. In continue, obtained ferrocenylsilane derivative was grafted to hydroxyl terminated polybutadiene (HTPB) via hydrosilylation reaction. Ferrocenyl units in polymer backbone gave a couple of reversible peaks of cyclic voltammetry (CV). Additionally, FT-IR, 1H NMR, UV–Vis spectroscopy along with molecular weight and TGA analysis confirmed the polymer modification. The modified polymer was coated onto the surface of glassy carbon electrode (GCE); meanwhile, fresh egg white (FEW) and terephthaldehyde (TFA) were used as cross-linking agents. The successful immobilization of polymer was demonstrated using Electrochemical impedance spectroscopy (EIS). The modified electrode showed an electrocatalytic effect on the oxidation of DA, the Fc/Fc+ couple mediate the oxidation of DA on the surface of GC/Butacene/(TFA + FEW) electrode. The optimum pH = 7 was obtained for this response. The electrode protected 86% of its initial electrocatalytic after 500 cycles and 90% of its initial current after 30 day storage at 4 °C. The results indicated that GC/Butacene/(TFA + FEW) electrode possessed satisfactory linear ranges and detection limits for detection of DA.

Synthesis of ferrocenyl‐containing silicone rubbers via platinum‐catalyzed Si–H self‐cross‐linking

Self‐cross‐linkable ferrocenyl‐containing polymethylhydrosiloxanes were synthesized. Karstedt's catalyst and cis‐[PtCl2(BnCN)2] were examined as cross‐linking catalysts at room temperature for the reaction between Si–H groups of the ferrocenyl‐containing polymethylhydrosiloxanes. Cis‐[PtCl2(BnCN)2] is an effective catalyst that allows cross‐linked ferrocenyl‐containing silicones (silicone rubbers) to be obtained with no visible mechanical defects (bubbles or cracks) compared with Karstedt's catalyst. The ferrocene content of the ferrocenyl‐containing silicone rubbers was found to be approximately 50 wt.% by energy‐dispersive X‐ray analysis. Compared with cross‐linked non‐modified polymethylhydrosiloxanes, the ferrocenyl‐containing silicone rubbers exhibited improved tensile properties (the tensile strength increased from 0.47 to 0.75 MPa) and a 1.5–2.5 times lower cross‐linking degree. The surface resistivity of the ferrocenyl‐containing silicone rubbers (50 wt.% ferrocenyl units) was approximately 7 × 109 Ω/□, which was 10,000 times lower than that of pure polymethylhydrosiloxane. The obtained flexible electroactive ferrocenyl‐containing silicone rubbers can potentially be applied as coatings for electronic and electrostatic‐sensitive devices, interfaces, and sensors.

Excited-state investigations of meso-mono-substituted-(amino-ferrocenyl)porphyrins: Experimental and theoretical approaches

The spectroscopic study and characterization of mono-(amino-ferrocenyl) porphyrins has increased during the last years. These molecules can be synthesized in such a way that their linear and nonlinear optical parameters are modulated, opening the possibility for new applications, such as in photodynamic therapy. In this work, we perform a spectroscopic characterization of a group of five free-base porphyrins, three of them having a C6F4 group attached to an amino-ferrocene moiety through a −NH(CH2)nNH− spacer, in which n = 2, 4 or 6. These three molecules differ by the size of the aliphatic chain. For this study, we employ linear as well as nonlinear optical spectroscopic techniques, such as the Z-Scan and time resolved fluorescence. Decay times, absorption cross-sections and quantum yields were determined, and the results suggest that, for this group of molecules, the differences in the aliphatic chain sizes joining the ferrocenyl unit to the C6F4 group at the para-position aryl ring do not influence significantly the optical parameters. Further, DFT calculations confirm that the UV–vis absorbance and the associated electronic transitions are not affected by the size of the aliphatic chain spacers. Thus, it is possible to state that these molecules can interact with biomolecules through the ferrocene unit while keeping their optical properties unchanged.

Molecular recognition: Evidence of the redox role of ferrocenyl-imine derivatives in the presence of copper (II) ions

The design and development of new selective and sensitive chemosensors for metal ions is an area of intense research activity due to their important roles in medicine, living systems, and the environment. In this work, novel ferrocenyl derivatives functionalized with a crown ether linked via an olefin-imine spacer have been designed as versatile molecular recognizers for a series of metal ions (Na+, Ca+2, Cu2+, and Cd2+). By using UV-vis titrations, these systems showed a high affinity for Cu2+ among other metal ions, nevertheless, with unexpected optical behavior. With Spectroelectrochemical studies and electrochemical titrations we revealed that redox reactions between the ferrocenyl and the imine moieties of the spacer and the copper ions took place. These experimental results prove a redox reaction mechanism between both ferrocenyl and imine moieties in the presence of Cu2+. Therefore, this work puts a notice about the redox reaction that takes place between copper (II) and ferrocenyl-imine derivatives, and this information should be considered when designing metal ion chemosensors based on ferrocenyl and imine units, because this redox interaction would become a possible competition reaction.

Mapping Conformational Changes in a Self-Assembled Two-Dimensional Molecular Network by Statistical Analysis of Conductance Images

A self-assembled two-dimensional (2D) film of tetra-phenyl-porphyrin-4-ferrocene molecules on Au(111) is studied by STM for the presence of intra- and intermolecular correlations in the configurations of the four-pendant ferrocenyl moieties. A statistical analysis of STS images exploits the Pearson’s linear correlation coefficient derived from changes in the molecular electron density across lateral positions in the molecular network as a measure of the intra- and intermolecular coupling and/or conjugation between adjacent equivalent molecular components. Density functional theory (DFT) calculation shows that these electron density changes can be assigned to conformational changes of the ferrocenyl units of the molecules. The methodology presented here can be extended to measure correlations in other 2D systems.

Synthesis, Spectroscopy, and Redox Studies of Ferrocene-Functionalized Coinage Metal Alkyne Complexes.

Ethynylferrocene (FcC≡CH) was utilized as a redox-active metalloligand for the synthesis of polynuclear coinage metal complexes. The reaction of [FcC≡CLi] with tri- tert-butylphosphine metal chlorides [tBu3P-MCl] (M = Au, Ag, Cu) yielded different heteronuclear ferrocene-funtionalized alkyne complexes featuring metallophilic interactions. Furthermore, the redox properties of the ferrocenyl-functionalized tetracopper complex were investigated by cyclic voltammetry and UV-vis-near-IR spectroelectrochemistry. They indicate the compounds' redox-rich nature and a weak electronic coupling between the redox-active ferrocenyl units over a large distance.

Homo- and heterobimetallic azines derived from ferrocene and cyrhetrene: Synthesis, structural characterization and electrochemical studies

A new series of asymmetrical heterobimetallic azines [(η5-C5H5)Fe{(η5-C5H4)C(R) = NNC(R1)-(η5-C5H4)Re(CO)3}] (1–3) and symmetrical homobimetallic cyrhetrenyl azines [{(η5-C5H4)C(R) = N}Re(CO)3]2 (4, 5) have been synthesized and were spectroscopically characterized by FT-IR, NMR, EI-MS and cyclic voltammetry. The molecular structures of 1 and 4 were determined using single-crystal X-ray diffraction technique. Based on the oxidation potential of the ferrocenyl units and the high degree of planarity of the [(C5H4)C(H) = NNC(H)-(C5H4)] system in complex 1, we inferred electronic communication between the electron-withdrawing cyrhetrenyl groups through the π-conjugated azine bridge. The compounds display an (E,E)-configuration about the >CN- bond, an s-trans conformation for the NN bond and an anti-conformation for the two organometallic fragments.

Ferrocenyl‐Functionalized η5‐Thiophene Cr(CO)3 Half‐Sandwich Compounds

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.

Cationic tri(ferrocenecarbonitrile)silver(I)

AbstractThe synthesis of the tri-coordinated ferrocenecarbonitrile silver(I) complex [Ag(N≡CFc)3]OTf (3) is reported. Its electrochemical behavior shows that the three ferrocenyl units are oxidized in a very close potential range. In addition, the molecular structure of3in the solid state is discussed, showing that silver(I) is exclusively coordinated by three ferrocenecarbonitrile molecules.

Acido-triggered switching of the second-order nonlinear optical properties of a ferrocenyl-containing indolino-oxazolidine derivative

The synthesis and the characterization of the linear and second-order nonlinear optical properties are reported for a new derivative of the indolino-oxazolidine family, which exploits the strong donor capacity of the ferrocenyl unit. Hyper-Rayleigh scattering experiments show that the pH-triggered switching between the closed and protonated open form of this compound enhances the first hyperpolarizability by roughly a factor 5, as a result of the increase of the push-pull π-electron conjugation within the molecule, between the donor ferrocenyl unit and the acceptor indoleninium moiety. Although derivatives exhibiting larger β responses in their nonlinear optical active form and larger βPOF/βCF contrasts were previously reported within this class of materials, the figure of merit of this ferrocenyl-based compound is high enough for device application. Quantum chemical calculations of the linear and nonlinear optical properties are at least in qualitative agreement with the experimental trends. Calculations also show that β of the protonated open form originates from two low-lying excited states, of which the contributions partly cancel each other due to the opposite directions of the photo-excited charge transfer.

Development of a Novel Ferrocenyl Histone Deacetylase Inhibitor for Triple-Negative Breast Cancer Therapy

Owing to the lack of target-directed therapies, triple-negative breast cancer (TNBC) is difficult to effectively treat. In this article, a novel organometallic histone deacetylase (HDAC) inhibitor, Fc-SelSA, based on the selenocyanide (SelSA) zinc-binding motif, was synthesized using a ferrocenyl group as the cap to confer activity against TNBC. The synthesized Fc-SelSA was evaluated for bioactivity in vitro and in vivo. An enzymatic assay showed that Fc-SelSA was a potent HDAC inhibitor with a half-maximum inhibitory concentration (IC50) of 14.8 nM. Molecular docking studies of Fc-SelSA with HDAC suggested that the ferrocenyl unit overlaps with the phenyl group of suberoylanilide hydroxamic acid (SAHA) and the amido group of Fc-SelSA can form hydrogen bonds with the D98 and G151 residues of HDAC, but SAHA and SelSA do not show similar interactions. Moreover, Fc-SelSA reactivated the estrogen receptor alpha (ERα) expression, sensitized TNBC cells to the antagonist tamoxifen, and exerted more potent antitu...

4,5-Diferrocenyl-1,2-dithiol-3-one

The title compound, [Fe2(C5H5)2(C13H8OS2)], crystallizes with two molecules in the asymmetric unit. Each molecule comprises a pair of ferrocenyl units bridged by a dithiol-3-one moiety. The dihedral angles between the dithiol-3-one ring and the substituted cyclopentadienyl rings are in the range 32.4 (3)–39.3 (3)°. One of the dithiol-3-one rings was refined as being disordered over two sets of sites while the same kind of disorder in the other molecule was negligible. The molecular packing is dominated by C—H...O hydrogen bonds and C—H...π interactions.

New thiazolidine‐2,4‐dione derivatives combined with organometallic ferrocene: Synthesis, structure and antiparasitic activity

Favourable physicochemical properties of an organometallic ferrocene and antiplasmodial potency of compounds containing the thiazolidine‐2,4‐dione framework (TZD‐4) prompted us to explore compounds containing both the thiazolidine‐2,4‐dione core and the ferrocenyl unit with the primary aim of identifying compounds with promising antiprotozoal activities. Thus, a new series of rationally designed ferrocene‐based thiazolidine‐2,4‐dione derivatives, containing a selection of secondary cyclic amines, was synthesised and fully characterised using standard spectroscopic techniques. The resulting compounds were screened for their antiplasmodial and antitrypanosomal activities against both the chloroquine‐resistant (Dd2) strain of Plasmodium falciparum and the Nagana Trypanosoma brucei brucei 427. The general trend that emerged indicated that the target compounds were more selective towards T. b. brucei compared to the P. falciparum parasite. Moreover, the analogues bearing methylpiperazine (8a) and piperidine (8b) rings were more active against T. b. brucei compared to hit compound TZD‐4. Except compound 8b, which appeared promising, none of the synthesised compounds showed better activity than TZD‐4 against the P. falciparum parasite. All the synthesised compounds were non‐toxic and often showed >90% viability of the HeLa cell line screened.

Synthesis, spectroscopic/electrochemical characterization and DNA interaction study of novel ferrocenyl‐substituted porphyrins

We report the synthesis and characterization of two new meso‐ferrocenylporphyrins, with the ferrocenyl unit attached at the para position of a C6F4 group by a CN bond with NH(CH2)2NH (2a) and NH(CH2)4NH (2b) spacers. Compounds 2a and 2b were characterized through elemental analyses, electrospray ionization high‐resolution mass spectrometry, 1H NMR, UV–visible and fluorescence spectroscopies, electrochemistry and spectroelectrochemistry. The free base porphyrin 2 was included for comparison purposes. The binding ability of 2 and the porphyrin derivatives 2a and 2b with calf thymus DNA was determined using UV–visible and fluorescence spectroscopies. The results suggest that the interaction of these systems most probably occurs through π‐stacking by non‐classical modes involving the partial insertion of the C6F5 ring between adjacent base pairs on DNA and possible hydrogen interaction with the aliphatic NH(CH2)nNH (n = 2 or 4) groups with calf thymus DNA. Moreover, we also demonstrate that porphyrins generate singlet oxygen species and show good photostability after irradiation.

Electronic Interactions between Ferrocenyl Units Facilitated by the Cobalt Bis(dicarbollide) Anion Linker: An Experimental and DFT Study

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.

Novel Pyrazoline‐based Organometallic Compounds Containing Ferrocenyl and Quinoline units: Synthesis, Characterization and Microbial susceptibilities

Some novel pyrazoline‐based organometallic compounds were synthesized as new leads in antimicrobial chemotherapy. The structures of compounds were elucidated by different spectroscopic techniques and elemental analyses. All compounds were investigated for in vitro antimicrobial studies against fifteen ATTC bacterial and fungal strains. The microbial susceptibility of these compounds revealed that all the tested compounds gave good minimum inhibitory concentration (MIC) values against the tested organisms that are either similar or even better than the reference drugs amoxicillin and fluconazole, which gave MIC values 8‐64 μg/ml against bacterial and 64 μg/ml against fungal strains, respectively. Among all compounds, compound (4d)1‐(5‐(4‐chlorophenyl)‐3‐ferrocenyl‐4,5‐dihydropyrazol‐1‐yl)‐2‐quinolin‐8‐yloxy) ethanone, emerged out the most promising antimicrobial organometallic derivative with MIC values against all the strains ranging from 8‐32 μg/ml. Other compounds gave a range of MIC values between 16‐64 μg/ml against S. bovis, 16‐32 μg/ml against E. coli, and C. tropicalis except compound (4d) which gave MIC 8 μg/ml against S. bovis and E. coli, whereas 32 μg/ml against C. tropicalis. Collectively, these compounds gave a lower MIC value between 32‐64 μg/ml against both of the biofilm forming strains namely, P. aeruginosa and S. mutans. The results of microbial susceptibility concluded that these novel organometallic compounds are new leads in antimicrobial chemotherapy and can be very useful for further optimization work on microbial chemotherapy.

Anodic electrochemistry of mono- and dinuclear aminophenylferrocene and diphenylaminoferrocene complexes.

Two related three-membered series of nonlinear aminophenylferrocene and diphenylaminoferrocene complexes were prepared and characterized by 1H and 13C NMR spectroscopy. The first series consists of 4-(diphenylamino)phenylferrocene (TPA-Fc, 1a), its dimethoxy-substituted tetraphenylphenylenediamine derivative (M2TPPD-Fc, 1c), and the triphenylamine-bridged bis(ferrocenyl) complex (Fc-TPA-Fc, 1b). The second series involves bis(4-methoxyphenyl)aminoferrocene (M2DPA-Fc, 1d), 4-methoxyphenylaminoferrocene (MPA-Fc) with N-phenyl-appended terminal TPA (1e), and the corresponding bis(MPA-Fc) complex with bridging TPA (1f). The structure of complex 1d was further confirmed by single crystal X-ray diffraction. Combined investigations, based on anodic voltammetry, UV-vis-NIR spectroelectrochemistry and density functional theory (DFT) calculations, were conducted to illustrate the influence of the integration of multiple redox-active components on the sequential oxidation of these complexes. The first anodic steps in 1a-1f are localized preferentially on the ferrocenyl units, followed by oxidation of the TPA or TPPD moieties (absent in 1d). Irreversible oxidation of the ferrocene-appended strong donor DPA/MPA units in 1d-1f terminates the anodic series. The one-electron oxidation of the triphenylamine-bridged diferrocenyl (1b) and bis(phenylaminoferrocenyl) (1f) complexes triggers their facile redox disproportionation to dicationic bis(ferrocenium) products.

CAN catalysis and click chemistry routes in the synthesis of carborane-containing ferrocenes

CAN-catalyzed reactions between α-ferrocenyl ethanol or ferrocenyl methanol and S-, N- and O-carborane nucleophiles are reported. This approach is an efficient and simple procedure for the preparation of carborane derivatives containing ferrocenyl units. Energy and geometry optimizations of some carboranylthio-, carboranylamino- and carboranyloxy-substituted ferrocenes have been calculated using the density functional theory. A series of new ferrocene-containing carborane 1,2,3-triazoles have been synthesized in good yields through a facile copper-mediated 1,3-dipolar cycloaddition reactions of alkynyl ferrocenes with [(o-carboran-1-yl)methyl]azide. Molecular structure of carborane-substituted ferrocenyl triazole was established by single crystal X-ray diffraction study. Representative examples of all ferrocenyl carboranes prepared were characterized by IR, 1H and 11B NMR spectroscopy.

Benzodithiophene and Benzotrithiophene as π Cores for Two‐ and Three‐Blade Propeller‐Shaped Ferrocenyl‐Based Conjugated Systems

The syntheses of linear and star‐shaped bis‐ and tris(ferrocenyl) derivatives of benzo[1,2‐b:4,5‐b′]dithiophene and benzo[1,2‐b:3,4‐b′:5,6‐b′′]trithiophene are achieved through one‐pot CuI/TMEDA‐catalyzed (TMEDA = tetramethylethylenediamine) multiple annulations of bromoethynylbenzenes with sodium sulfide. In addition, the preparation of the parent benzotrithiophene in a good yield with a short reaction time is achieved through the threefold annulation of 1,3,5‐trifluoro‐2,4,6‐tris(trimethylsilyl)ethynylbenzene. The computed structural and electronic features of these ferrocenyl derivatives as well as their UV/Vis spectra and electrochemistry are discussed, and the results provide insights into the effect of the presence of three rather than two ferrocenyl units. To the best of our knowledge, 2,5,8‐tris(ferrocenyl)benzo[1,2‐b;3,4‐b′;5,6‐b′′]trithiophene is the first organometallic complex containing benzotrithiophene.

Near-infrared absorbing metal functionalized diketopyrrolopyrroles

A symmetrical cobalt-dithiolene functionalized diketopyrrolopyrrole (DPP) Co-DPP-Co was designed and synthesized. Its photophysical, thermal, electrochemical and computational studies were compared with symmetrical ferrocenyl Fc-DPP-Fc. The electronic absorption spectrum of Co-DPP-Co exhibited absorption in Vis-NIR region with shoulder band in longer wavelength region. The thermogravimetric analysis shows good thermal stability of Co-DPP-Co. The density functional theory (DFT) investigation exhibited the cis geometry of cobalt-dithiolene ring with respect to DPP in Co-DPP-Co whereas trans geometry was observed for ferrocenyl unit in Fc-DPP-Fc.