Abstract
[{RuCl3(dppb)}2(µ-4,4'-bipy)] was prepared from the reaction of the 4,4'-bipyridine and mer-[RuCl3(dppb)].H2O, in good yield. The characteristics of the binuclear complex studied with FT-IR, UV-Vis, EPR and elemental analysis were similar to those of the [RuCl3(dppb)L] (L= N-heterocycle). [{RuCl3(dppb)}2(µ-4,4'-bipy)] is soluble in weakly polar organic solvents, facilitating its use in the production of Langmuir and Langmuir-Blodgett (LB) films production. While the cast films and the complex in solution were red, the LB films were green-bluish, probably due to oxidation of the bisphosphine. The nanostructured nature of the LB films was manifested in electrochemical measurements, as these films exhibited higher peak currents than cast or dip-coated films. For all films, the electrochemical response was dominated by the RuIII RuIII/RuII RuII process, which differed from that of the binuclear compound. For the latter, an irreversible process appeared due to formation of new species. The electroactivity of LB films from [{RuCl3(dppb)}2(µ-4,4'-bipy)] also pointed to their possible use in electrochemical devices.
Highlights
The molecular organization was extracted from the information provided by surface pressure-molecular area (π-A) isotherms, atomic force microscopy (AFM), UV-vis absorption, FT-IR, reflection-absorption infrared spectroscopy (RAIRS), Raman scattering, and fluorescence.[4,27,28]
We present a detailed study of the binuclear complex, [{RuCl3(dppb)}2(μ-4,4’-bipy)] (4,4’-bipy= 4,4’-bipyridine), used in the fabrication of Langmuir and LB films whose properties will be compared to those of a mononuclear derivative
The IR spectra of the powdered complex were recorded from CsI pellets in the 4000-200 cm-1 region and the IR spectra of the LB films were recorded from films with 61 monolayers deposited onto Si wafers
Summary
Cyclic voltammetry (CV) experiments of the complex in solution were obtained in a BAS-100B/W Bioanalytical Systems Instrument. These experiments were carried out at room temperature in CH2Cl2 containing 0.10 mol L-1 Bu4N+ClO4– (TBAP) (Fluka Purum) as support electrolyte using a one-compartment cell where the working and auxiliary electrodes were stationary Pt foils, and the reference electrode was Ag/AgCl, 0.10 mol L-1 TBAP in CH Cl , a medium in which ferrocene is oxidized at 0.43 V (Fc+/Fc). The electrochemical measurements of LB films were carried out in a Microquimica MQPG-01 potentiostat, using a 10 mL electrochemical cell with the conventional three-electrode system: a Pt wire as a counter electrode, an Ag/AgCl in KCl electrode as the reference and the LB (sat.). Redox potentials (E1⁄2) were determined from the average of the anodic and cathodic peak potentials (Epa and Epc)
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