André L. Bogado

Electropolymerized supramolecular tetraruthenated porphyrins applied as a voltammetric sensor

Porphyrin 5,10,15,20-Tetra(4-pyridyl)manganese(III), [Mn-TPyP(H2O)2]PF6, and electropolymerized supramolecular porphyrins (ESP), {Mn-TPyP(H2O)2[RuCl3(dppb)]4}PF6 (dppb = 1,4-bis(diphenilphosphine)butane), were synthesized and characterized. A thin solid film of ESP was obtained on a glass carbon electrode surface by a cyclic voltammetry method. The peak current increased with the number of voltammetric cycles, which shows a typical behavior of the species being adsorbed on the surface of the electrode. Cyclic voltammetry was also employed for acetaminophen quantification using an ESP modified electrode. The modified electrode shows a linear relationship between the anodic peak current and the concentration of acetaminophen (in the rage 0.05 to 0.7 mmol L - 1). The performance of the modified electrode was verified by the determination of acetaminophen in a commercial pharmaceutical product and the results were in good agreement with those obtained by a control HPLC method.

Influence of gold nanoparticles applied to catalytic hydrogenation of acetophenone with cationic complexes containing ruthenium

Herein the catalytic activity of cationic ruthenium(II) complexes [Ru]+ is described in the presence of gold nanoparticles (AuNPsn−) in the transfer hydrogenation of acetophenone, to produce phenylethanol. The catalytic activity of the complexes, with a general formula cis-[RuCl(CH3OH)(P–P)(N–N)]+ or cis-[RuCl(CH3OH)(P)2(N–N)]+ {where: P = triphenylphosphine (PPh3); P–P = 1,1-bis(diphenylphosphino)methane (dppm); 1,2-bis(diphenylphosphino)ethane (dppe); 1,3-bis(diphenylphosphino)propane (dppp), 1,4-bis(diphenylphosphino)butane (dppb); N–N = 2,2′-bipyridine; 4,4′-dimethyl-2,2′-bipyridine} was investigated in the presence of AuNPsn−. The interaction between [Ru]+ and AuNPsn− citrate capped is an electrostatic interaction, by a self-assembly processes, to produce a supramolecular species, labeled as [Ru]+/AuNPsn−. This non-covalent interaction has no effect over the chemical and physical chemical parameters of the complexes, which provides a good point of comparison in the presence and absence of AuNPsn−. The AuNPsn− alone have no catalytic activity in the transfer hydrogenation of acetophenone within 24 h of reaction. However, the AuNPsn− have improved the catalytic activity of the complexes that have biphosphines with tensioned or large bite angle, while for the complexes that have biphosphines with a strong chelate effect a decrease in the catalytic activity was observed. The evidence is supported by experimental values of the yields of the hydrogenated product and DFT calculations of the “RuP–P” intermediates. Suitable crystals of cis-[RuCl2(dppe)(bipy)], cis-[RuCl2(dppp)(bipy)] and cis-[RuCl(CH3OH)(dppb)(bipy)](PF6) were obtained and the X-ray structures are presented here.

An electronic device based on gold nanoparticles and tetraruthenated porphyrin as an electrochemical sensor for catechol

The aim of this study was to obtain an electrochemical device between the electrostatic interaction of the electropolymerized porphyrin {CoTPyP[RuCl3(dppb)]4}, where TPyP = 5,10,15, 20-tetrapyridilphorphyrin and dppb = 1,4-bis(diphenylphosphino)butane, and gold nanoparticles (AuNPsn−), to be used as a voltammetric sensor to determine catechol (CC). The modified electrode, labelled as [(CoTPRu4)n8+-BE]/AuNPsn− {where BE = bare electrode = glassy carbon electrode (GCE) or indium tin oxide (ITO)}, was made layer-by-layer. Initially, a cationic polymeric film was generated by electropolymerization of the {CoTPyP[RuCl3(dppb)]4} onto the surface of the bare electrode to produce an intermediary electrode [(CoTPRu4)n8+-BE]. Making the final electronic device also involves coating the electrode [(CoTPRu4)n8+-BE] using a colloidal suspension of AuNPsn− by electrostatic interaction between the species. Therefore, a bilayer labelled as [(CoTPRu4)n8+-BE]/AuNPsn− was produced and used as an electrochemical sensor for CC determination. The electrochemical behaviour of CC was investigated using cyclic voltammetry at [(CoTPRu4)n8+-GCE]/AuNPsn− electrode. Compared to the GCE, the [(CoTPRu4)n8+-GCE]/AuNPsn− showed higher electrocatalytic activity towards the oxidation of CC. Under the optimized conditions, the calibration curves for CC were 21–1357 µmol l−1 with a high sensitivity of 108 µA µmol l−1 cm−2. The detection limit was 1.4 µmol l−1.