Testing the Conjugative Properties of Benzodithiophene and Benzotrithiophene in Charge Transfer Multi(ferrocenyl) Systems

The charge transfer properties of the mono-, di-, and tricationic derivatives of bis(ferrocenyl)benzodithiophene and tris- (ferrocenyl)benzotrithiophene were investigated. The cations were generated by chemical oxidation using ferrocenium(BF4) and acetylferrocenium(BF4) as the oxidative agents and monitored in the visible and NIR regions. By changing the supporting electrolyte from [nBu4N][PF6] to [nBu4][B(C6F5)4], we were able to selectively generate the monocationic species of bis- and triferrocenyl complexes. The redox and optical properties of the cationic derivatives were rationalized by an in-depth electrochemical and optical study. The comparison with the results previously obtained for the structurally related bis(ferrocenyl)-s-indacene and tris(ferrocenyl)-trindene allowed for the evaluation of the huge influence of thiolation on the metal 12metal electronic coupling

Charge Transfer Properties of Benzo[b]thiophene Ferrocenyl Complexes

The synthesis of 2-ferrocenylbenzo[b]-thiophene, 3-ferrocenylbenzo[b]thiophene, 1,1-bis(2-indene)-ferrocene, and the two isomers of 1,1'-bis(2-benzo[b]-thiophene)ferrocene was efficiently achieved by using the palladium-catalyzed Negishi C,C cross-coupling reaction of the appropriate bromobenzo[b]thiophene derivative with ferrocenylzinc chloride. The accessibility of differently substituted benzo[b]thiophenes and a comparison with indene analogues allowed an in-depth investigation on how the geometric modifications and the presence of sulfur affect their physical properties. The molecular structure of 3-ferrocenylbenzo[b]-(t)hiophene has been determined by X-ray diffraction. Electrochemistry and UV-vis-NIR spectroscopy, in particular the appearance upon oxidation of a charge transfer absorption in the NIR region, are rationalized through quantum chemistry calculations and in the framework of the Hush theory

Hydrogen-bond-assisted, concentration-dependent molecular dimerization of ferrocenyl hydantoins

The synthesis and characterization of the ferrocenyl methylhydantoin 5-ferrocenyl-5-methylimidazolidine-2,4-dione, efficiently prepared through a Bucherer-Bergs reaction, and its derivatives carrying tert-butoxycarbonyl (Boc) protecting groups, namely 1,3-bis(tert-butoxycarbonyl)-5-ferrocenyl-S-methylirnidazolidine-2,4-dione and 1-(tert-butoxycarbonyl)-5-ferrocenyl-5-methylimidazolidine-2,4-dione, are reported. X-ray diffraction and ESI-mass spectrometry analyses of the ferrocenyl methylhydantoin revealed the presence of C=O center dot center dot center dot H-N intermolecularly hydrogen-bonded dimers. The mono-Boc derivative formed a hydrogen-bonded dimer in solution, as confirmed by H-1 NMR, FT-IR, and cyclic voltammetry experiments at different concentrations in CDCl3 or CHCl3

Endogenous Urotensin II Selectively Modulates Erectile Function through eNOS

Urotensin II (U-II) is a cyclic peptide originally isolated from the neurosecretory system of the teleost fish and subsequently found in other species, including man. U-II was identified as the natural ligand of a G-protein coupled receptor, namely UT receptor. U-II and UT receptor are expressed in a variety of peripheral organs and especially in cardiovascular tissue. Recent evidence indicates the involvement of U-II/UT pathway in penile function in human, but the molecular mechanism is still unclear. On these bases the aim of this study is to investigate the mechanism(s) of U-II-induced relaxation in human corpus cavernosum and its relationship with L-arginine/Nitric oxide (NO) pathway.Human corpus cavernosum tissue was obtained following in male-to-female transsexuals undergoing surgical procedure for sex reassignment. Quantitative RT-PCR clearly demonstrated the U-II expression in human corpus cavernosum. U-II (0.1 nM-10 µM) challenge in human corpus cavernosum induced a significant increase in NO production as revealed by fluorometric analysis. NO generation was coupled to a marked increase in the ratio eNOS phosphorilated/eNOS as determined by western blot analysis. A functional study in human corpus cavernosum strips was performed to asses eNOS involvement in U-II-induced relaxation by using a pharmacological modulation. Pre-treatment with both wortmannin or geldanamycinin (inhibitors of eNOS phosphorylation and heath shock protein 90 recruitment, respectively) significantly reduced U-II-induced relaxation (0.1 nM-10 µM) in human corpus cavernosum strips. Finally, a co-immunoprecipitation study demonstrated that UT receptor and eNOS co-immunoprecipitate following U-II challenge of human corpus cavernosum tissue.U-II is endogenously synthesized and locally released in human corpus cavernosum. U-II elicited penile erection through eNOS activation. Thus, U-II/UT pathway may represent a novel therapeutical target in erectile dysfunction

Key multi(ferrocenyl) complexes in the interplay between electronic coupling and electrostatic interaction

In this review, the properties of the most significant examples of multi(ferrocenyl) cations containing a number of ferrocenyl units from two to six are discussed and the results are compared with the outcomes of some of our recent studies on conjugated ferrocenyl complexes, in order to give an overview of how the nature of the bridging ligand, the distance between the redox-active centres, and the medium affect the electronic and electrostatic properties of the molecule

Charge Transfer Properties of Multi(ferrocenyl)trindenes

Ferrocenyl, diferrocenyl, and triferrocenyl complexes of dihydro-1H-trindene have been prepared by up to 3-fold bromide substitution of the dihydro-2,5,8-tribromo-1H-trindene halocarbon. The charge transfer properties of their mono-, di-, and tricationic derivatives were investigated. The cations of this new family of multi(ferrocenyl)trindene complexes were generated by chemical oxidation using (acetylferrocenium)(BF4) as the oxidative agent and monitored in the visible, IR and near-IR regions. The charge transfer bands in the near-IR spectra are rationalized in the framework of the Marcus\u2013Hush theory. In particular, the triferrocenyl complexes display a redox chemistry that can be switched from a unresolved three-electron oxidation to two consecutive one-electron and two near simultaneously occurring one-electron oxidations by changing the supporting electrolyte from [nBu4N][PF6] to [nBu4][B(C6F5)4]. In addition, the introduction of the third ferrocenyl group increases the strength of the metal\u2013metal interaction with respect to that of the structurally related diferrocenyl system

Mapping Charge Delocalization in a Peptide Chain Triggeredby Oxidation of a Terminal Ferrocene Moiety

Two series of peptides of different length and rigidity, based on the strongly helicogenic \u3b1-aminoisobutyric acid (Aib) residue and containing a terminal ferrocene (Fc) unit, Fc 12CO-(Aib)n 12OMe (An, n = 1 125, OMe, methoxy) and Z 12(Aib)n 12NH 12Fc (Bn, n = 1 125, Z, benzyloxycarbonyl), were prepared and investigated. We utilized the oxidation-state sensitive, spectroscopic tags of peptides, the CO and NH groups, to map charge delocalization triggered by oxidation of the terminal ferrocene

Single Two-Electron Transfers and Successive One-Electron Transfers in Biferrocenyl-Indacene Isomers

Novel biferrocenyl complexes of s- and as-dihydroindacenes have been prepared and the charge transfer properties of their mono- and dicationic derivatives, selectively generated by one-electron and two-electron oxidation, have been investigated. Mixed-valence cations are generated by chemical oxidation using acetylferricinium as an oxidant agent and monitored in the visible, IR, and near-IR regions. The IT bands in the near-IR spectra are rationalized in the framework of Marcus Hush theory. The rigid and planar indacene platform bonded to two terminal redox groups displays a redox chemistry that can be switched from single two-electron transfers to two successive one-electron transfers by changing the supporting electrolyte from nBu(4)NPF(6) to nBu(4)NB(C(6)F(5))(4)

Mapping charge delocalization in a peptide chain triggered by oxidation of a terminal ferrocene moiety

Two series of peptides of different length and rigidity, based on the strongly helicogenic \u3b1-aminoisobutyric acid (Aib) residue and containing a terminal ferrocene (Fc) unit, Fc 12CO-(Aib)n 12OMe (An, n = 1 125, OMe, methoxy) and Z 12(Aib)n 12NH 12Fc (Bn, n = 1 125, Z, benzyloxycarbonyl), were prepared and investigated. We utilized the oxidation-state sensitive, spectroscopic tags of peptides, the CO and NH groups, to map charge delocalization triggered by oxidation of the terminal ferrocene

Charge Transfer Properties in Cyclopenta[l]phenanthrene Ferrocenyl Complexes

The new complexes (2-ferrocenyl)cyclopenta[l]-phenanthrene and (2-ferrocenyl)(eta(5)-cyclopenta[l]phenanthrenyl)FeCp have been prepared and the charge transfer properties of their monocationic derivatives investigated. The cations were generated by chemical oxidation using ferrocenium(BF4) or acetylferrocenium(BF4) as the oxidative agent and monitored in the visible, IR, and near-IR regions. The electrochemistry of the two complexes and, for comparison, of the previously reported (eta(5)-cyclopenta[l]phenanthrenyl)FeCp was analyzed. The charge transfer bands in the near-IR spectral region of the monocations are rationalized in the framework of Marcus-Hush theory. In particular, the monometallic (2-ferrocenyl)cyclopenta[l]phenanthrene displays a single oxidation wave at a potential very close to that of (eta(5)-cyclopenta[l]phenanthrenyl)FeCp and its monocations exhibits a ligand-to-metal charge transfer band in the visnear-IR region. The unsymmetrical diiron species (2-ferrocenyl)(eta(5)-cyclopenta[l]phenanthrenyl)FeCp undergoes two consecutive and well-resolved one-electron oxidations producing, at the first oxidation step, a mixed-valence monocation which displays an intervalence charge transfer band in the vis-near-IR region