title: Electrochemical and spectroscopic behavior of iron(III) porphyrazines in Langmuir-Schafer films.
abstract: Thin films of a newly synthesized iron(III) porphyrazine, LFeOESPz ( L = ClEtO, OESPz = ethylsulfanylporphyrazine), have been deposited by the Langmuir-Schafer (LS) technique (horizontal lifting) on ITO or gold substrates. Before deposition, the floating films have been investigated at the air-water interface by pressure/area per molecule (pi/ A) experiments, Brewster angle microscopy (BAM) and UV-vis reflection spectroscopy (RefSpec). The complex reacts with water subphase (pH 6.2) forming the mu-oxo dimer, which becomes the predominant component of the LS films ( LS-Fe) as indicated by optical, IR, XPS, and electrochemical data. LS-Fe multilayers exhibit, between open circuit potential (OCP) and +0.90 V (vs SCE), two independent peak pairs with formal potentials, E surf (I) and E surf(II) of +0.56 V and +0.78 V, respectively. According to dynamic voltammetric and coulometric experiments the peak pair at +0.56 V is attributed to one-electron process at the iron(III) centers on the monomer, while the peak pair at +0.78 V is associated to a four-electron process involving mu-oxo-dimer oligomers. LS-Fe films prove to be quite stable electrochemically between OCP and +0.90 V. The electrochemical stability decreases, however, when the potential range is extended both anodically and cathodically outside these limits, due to formation of new species. Upon incubation with TCA solutions, LS-Fe films show remarkable changes in the UV-vis spectra, which are consistent with a significant mu-oxo dimer --> monomer conversion. Addition of TCA to the electrochemical cell using a LS-Fe film as working electrode, results in a linear increase of a cathodic current peak near -0.40 V as the TCA concentration varies in the 0.1-2.0 mM range. This behavior is interpreted in terms of TCA inducing a progressive change in the composition of the LS-Fe films in favor of the monomeric iron(III) porphyrazine, which is responsible for the observed increase in the cathodic current near -0.40 V.
authors: Dipartimento di Chimica, Università della Basilicata, Via N. Sauro, 85, Potenza, Italia.
authors: Gaetano
authors: G
authors: Garramone
authors: Daniela
authors: D
authors: Pietrangeli
authors: Giampaolo
authors: G
authors: Ricciardi
authors: Sabrina
authors: S
authors: Conoci
authors: Maria Rachele
authors: MR
authors: Guascito
authors: Cosimino
authors: C
authors: Malitesta
authors: Daniela
authors: D
authors: Cesari
authors: Serena
authors: S
authors: Casilli
authors: Livia
authors: L
authors: Giotta
authors: Gabriele
authors: G
authors: Giancane
authors: Ludovico
authors: L
authors: Valli
mesh_terms: D002412:Cations; D019281:Dimerization; D004563:Electrochemistry; D007501:Iron / Q000737:chemistry*; D009942:Organometallic Compounds / Q000138:chemical synthesis*; D011166:Porphyrins / Q000737:chemistry*; D013057:Spectrum Analysis
chemical_list: D002412:Cations; D009942:Organometallic Compounds; D011166:Porphyrins; D007501:Iron