Two ruthenium complexes of the type [RuCl(dmso)(L)2]Cl {L = 4,4’-dimethyl-2,2’-bipyridine (dmbpy); 4,4’-dinonyl-2,2’-bipyridine (dnbpy)} have been synthesized and characterized by elemental analysis, 1H NMR, FTIR, electronic spectra, and molar conductivity. The IR spectral studies revealed that the DMSO molecule is S-bound ( νSO= 1100 cm-1; 1079 cm-1). For complexes, MLCT bands were observed around 390 nm and 440 nm. The measurements of conductivity revealed the presence of 1:1 electrolyte. Interactions of ruthenium complexes with human serum albumin were examined by fluorescence spectroscopy. The results revealed a combined quenching mechanism of HSA fluorescence by [RuCl(dmso)(dmbpy)2]Cl, with binding constant of 5.82 ± 0.08 x 105 mol-1 L (297 K), 5.29 ± 0.06 x 105 mol-1 L (303 K), and 4.68 ± 0.06 x 105 mol-1 L (313 K), whereas the [RuCl(dmso)(dnbpy)2]Cl caused static quenching predominantly, with binding constant of 9.87 ± 0.05 x 105 mol-1 L (297 K), 3.41 ± 0.04 x 105 mol-1 L (303 K), and 0.89 ± 0.05 x 105 mol-1 L (313 K). The binding process occurred spontaneously and was mainly driven by enthalpy, as evidenced by thermodynamic parameters. Site marker competitive experiment showed that ruthenium complexes bind to the warfarin binding site in subdomain IIA of HSA.

Zirconium-based metal-organic framework, UiO-67, was synthesized and used as support for the immobilization of the [RuCl2(ENAPY)] (ENAPY = N,N'-bis(7-metyl-2-pyridylmethylene)-1,2-diiminoethane)). The immobilized system exhibited violet-blue color. The {UiO-67/[RuCl2(ENAPY)]} was characterized by cyclic voltammetry, X-ray diffraction, UV-Vis, FTIR and X-ray photoelectron spectroscopy. The electrochemistry of the immobilized system is characterized by a reversible pair of waves at +0.40 V (vs NHE), ascribed to the Ru3+/2+ redox process. The electronic spectrum of the immobilized system is characterized by bands at 520 and 380 nm ascribed to a ligand-to-metal charge-transfer transitions {Ru2+(dπ) → ENAPY(pπ*)}. The IR bands of immobilized complex {1630 cm-1 (νasC=C), 1590 cm-1 (νasC=N), 1450 cm-1 (νsC=C), 1340 cm-1 (νsC=C)} are weak in comparison with the neat complex due to their low concentration in MOF cages. X-ray diffractogram of the immobilized system indicated that the crystallinity and morphology of UiO-67 was preserved during inclusion of ruthenium complex. The XPS spectra of UiO-67 and UiO-67/ruthenium complex shows a signal at 462 eV that can be ascribed to Ru 3p3/2 and at 400 eV ascribed to N 1s core level of the ruthenium Schiff base complex immobilized into MOF.

The binding of [RuCl2(L)] (L = N,N-bis(7-methyl-2-pyridylmethylene)-1,3-diiminopropane) to bovine and human serum albumin was investigated by the fluorescence quenching technique. The comparison of the quenching effect of serum albumin fluorescence by ruthenium complex allowed the estimation of subdomain IB in BSA and subdomain IIA in HSA as the binding sites for this complex. The results of fluorescence titration revealed that ruthenium complex quenches the intrinsic fluorescence of BSA through a dynamic quenching mechanism, while HSA has a static quenching mechanism. The thermodynamic parameters indicated that hydrophobic forces played a major role in the binding of ruthenium complex to proteins. The process of binding was a spontaneous process in which Gibbs free energy change was negative.

Um eletrodo de carbono vítreo modificado com hexacianoferrato(II) de CrIII foi utilizado para a determinação de piridoxina (vitamina B6) em três diferentes fármacos, por voltametria cíclica. A influência de vários parâmetros na resposta voltamétrica do eletrodo foi analisada. A faixa linear encontrada foi de 1,33 × 10-6 mol L-1 a 1,32 × 10-5 mol L-1 da vitamina, com r = 0,9990 e desvio padrão relativo de 4,2%. Os limites de detecção e quantificação foram de 3,46 × 10-7 mol L-1 e 1,05 × 10-6 mol L-1, respectivamente. O método proposto para a determinação voltamétrica da vitamina B6 apresentou uma boa exatidão e os resultados experimentais demonstraram que o eletrodo de carbono vítreo modificado com hexacianoferrato(II) de CrIII apresenta um grande potencial para análise de piridoxina em amostras reais. Além disso, apresenta vantagens como uma resposta rápida, um baixo limite de detecção, baixo custo e simplicidade no desenvolvimento e aplicação.

A CrIII hexacyanoferrate(II) (CrHCF)-modified glassy carbon electrode was used to determine pyridoxine (vitamin B6) in three drugs by cyclic voltammetry. The influence of several parameters on the voltammetric electrode response was analyzed. The linear range found was of 1.33 × 10-6 mol L-1 to 1.32 × 10-5 mol L-1 of vitamin, with r = 0.9990 and relative standard deviation of 4.2%. The limits of detection and quantification were 3.46 × 10-7 mol L-1 and 1.05 × 10-6 mol L-1, respectively. The voltammetric proposed method for determination of vitamin B6 presented good accuracy and the experimental results demonstrated that the CrHCF-modified glassy carbon electrode has a large potential for the analysis of pyridoxine in real samples. Furthermore, it has the advantages of a fast response, a low detection limit, low cost, and simple development and application.