Karen Wohnrath

PHYSICO-CHEMICAL PARAMETER CORRELATIONS IN THE RUCL2(CO)(L)(PPH3)2 COMPLEXES (L = N-HETEROCYCLES)

Abstract Fourteen complexes in the series [RuCl2(CO)(L)(PPh3)2] (where L = N-heterocycles) have been prepared and characterized by IR and NMR spectroscopies, and cyclic voltammetry. A good correlation is found between observed and calculated electrochemical potentials; E 1 2 vs pKa or (Gp, σm for a series of similar ligands. It is now reported that the carbonyl stretching frequency, νCO, and the 13C and 31P NMR signals do not correlate well with any of the physico-chemical parameters used ( E 1 2 , Tafts and Hammetts parameters). This behaviour is probably due to the characteristics of the Ru(II) species, which does not transmit the steric and electron donor/acceptor properties of the ligands to the carbonyl group, or because the measurements are not able to detect the effect induced by the changes in the ligand L. Indeed, good correlations are obtained when the measurements directly involve the metal centre, as is the case in the E 1 2 measurements. Crystals of [RuCl2(CO)(4-pic)(PPh3)] are monoclinic, space group P21/n, a = 12.019(2), b = 13.825(3) and c = 22.253(3) . The structure was solved by the Patterson method and was refined by full-matrix least-squares procedure to R = 0.054 and Rw = 0.055, for 2114 reflections with I > 3σ(I). For L = 2-acetylpyridine and 2-methylimidazole, complexes with formulae [RuCl2(CO)(L)(PPh3)] · L and [RuC12(CO)(L)2 (PPh3)], respectively, were obtained.

Morphological characterization of Langmuir–Blodgett films from polyaniline and a ruthenium complex (Rupy): influence of the relative concentration of Rupy

We report on the use of dynamic scale theory and fractal analyses in a study of the growth stages of Langmuir?Blodgett (LB) films of polyaniline and a neutral biphosphinic ruthenium complex, namely mer-[RuCl3 (dppb)(py)] (dppb = 1,4-bis(diphenylphosphine)buthane, py = pyridine), Rupy. The LB films were deposited onto indium-tin-oxide substrates and characterized with atomic force microscopy. From the granular morphology exhibited by the films one could infer growth processes inside and outside the grains. Growth outside was found to follow the Kardar?Parisi?Zhang model, with fractal dimensions of about?2.7. As one would expect, inside the grains the morphology is close to a Euclidian surface with fractal dimension of about 2.

Simultaneous voltammetric determination of dopamine and ascorbic acid using multivariate calibration methodology performed on a carbon paste electrode modified by a mer-[RuCl3(dppb)(4-pic)] complex

The preparation and electrochemical characterization of a carbon paste electrode (CPE) modified with mer-[Ru0Cl3(dppb)(4-pic)] (dppb=Ph2P(CH2)4PPh2, 4-pic=CH3C5H4N), referred to as Rupic, were investigated. The CPE/Rupic system displayed only one pair of redox peaks, with a midpoint potential at 0.28 V vs. Ag/AgCl, which were ascribed to RuIII/RuII charge transfer. This modified electrode presented the property of electrocatalysing the oxidation of dopamine (DA) and ascorbic acid (AA) at 0.35 V and 0.30 V vs. Ag/AgCl, respectively. Because the oxidation for both AA and DA practically occurred at the same potential, distinguishing between them was difficult with cyclic voltammetry. This limitation was overcome using Partial Least Square Regression (PLSR), which allowed us, with the optimised models, to determine four synthetic samples with prediction errors (RMSEP) of 5.55´10-5 mol L-1 and 7.48´10-6 mol L-1 for DA and AA, respectively.

Electrochemical properties of mixed films of polyaniline and a ruthenium complex

The interactions between polyaniline (PANI) and mer-[RuCl 3 (PP)(py)] (PP= biphosphine, py= pyridine), Rupy, in cast films have been analyzed using cyclic voltammetry and the results are compared with those from Langmuir-Blodgett (LB) films. The mixed films were prepared from solutions containing 10 %, 30 %, 50 % in mol of Rupy. All cast films showed electroactivity, while for LB films an activity was observed only for the mixtures containing 10 % and 30 % of Rupy. The differences between cast and LB films are attributed to strong interactions in the LB films, which are absent in the cast films, probably owing to phase separation between Rupy and PANI aggregates. The order-induced color changes in the LB films are also absent in the cast films.

Electrochemical synthesis of the copolymer poly(2-methoxy-5-bromo-p-phenylenevinylene)/(2,5-dicyano-p-phenylenevinylene) (MB-PPV/DCN-PPV): tuning properties

The present work describes an electrochemical method to produce the copolymer poly(2-methoxy-5-bromo-p-phenylenevinylene)/(2,5-dicyano-p-phenylenevinylene) (cop-MB-PPV/DCN-PPV). This copolymer was proposed due to its D-A characteristic produced by the presence of the electron-donating methoxy moiety and the electron-withdrawing dicyano moiety. The copolymer was electrochemically synthetized by cathodic reduction of the convenient starting materials dissolved in a DMF/LiClO4 using a mercury pool acting as working electrode. The copolymer was characterized by infrared (IR), UV-Vis and fluorescence (FL) spectroscopy and cyclic voltammetry (CV). All the results were compared to the MB-PPV homopolymer. The analysis of electrochemical measurements and IR indicated that the cop-MB-PPV/DCN-PPV was obtained through the formation of blocks containing DCN-PPV units linked by blocks containing MB-PPV units. The electronic structure, performed by CV, UV-Vis and FL showed that the conduction band is more stabilized in the copolymer than in homopolymer. Furthermore, the FL spectra indicated that the light emission of the cop-MB-PPV/DCN-PPV in chloroform solution occurs by means of excimer formation.

Montmorillonite Silver Nanoparticles for Applications in Polymeric Materials

This work presents the preparation of silver nanoparticles (AgNPs) with montmorillonite to produce a nanomaterial with bactericidal properties. The modified montmorillonite was characterized through the techniques of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy and X-ray diffraction (XRD). The FTIR and Raman spectrum’s showed specific bands of involving stretching silver. In the XRD analyses was observed the occurrence of the following crystallographic planes (111), (200) e (220) silver related. The nanocomposites of polyethylene with AgNPs did not show loss in mechanical properties, this fact was important and indicate that the nanomaterial can be inserted in this polymer matrix with considerable technological interest.

SÍNTESE E CARACTERIZAÇÃO DE NANOPARTÍCULAS DE PRATA NO POLIELETRÓLITO CLORETO DE 3-N-PROPILPIRIDÍNIO SILSESQUIOXANO PARA APLICAÇÃO EM MATERIAIS TÊXTEIS DOI: 10.5212/Publ.Exatas.v.18i1.0005

No presente trabalho foi realizada a sintese e a caracterizacao das nanoparticulas de prata (AgNps), utilizando-se o polieletrolito cloreto de 3-n-propilpiridinio silsesquioxano (SiPy+Cl-) como nanoreator e a aplicacao dessas nanoparticulas para incorporacao em materiais texteis. As sinteses das AgNps foram realizadas pelo metodo de precipitacao, utilizando-se o AgNO3 como precursor, o polieletrolito (SiPy+Cl-) como estabilizante e o NaBH4 como agente redutor. A sintese foi realizada em quatro proporcoes (1%, 2%, 5% e 10% m/V de prata em relacao ao polieletrolito) e a formacao, estabilidade e tamanho das nanoparticulas foram analisadas por espectroscopia de UV-Vis e Potencial Zeta. Observou-se que na presenca do SiPy+Cl-, a banda plasmonica das AgNps, na regiao de 350- 450 nm, apresentou-se deslocada para maiores comprimentos de onda, o que pode estar associado a interacao do SiPy+Cl- com as AgNps ou a diferenca de tamanho das nanoparticulas estabilizadas em relacao as AgNps livres. As nanoparticulas obtidas nas proporcoes 5% e 10% m/V apresentaram-se mais estaveis, com tamanhos medios de aproximadamente 25 a 45 nm. A partir dos espectros de infravermelho com transformada de Fourier (FTIR), pode-se constatar um decrescimo na intensidade das bandas em 1634 e 1484 cm-1 referente as vibracoes do anel piridinio apos a incorporacao das AgNps, evidenciando interacoes entre eles. O tamanho medio dos cristalitos, calculado pela equacao de Scherer, foi de 42 nm e 48 nm para as amostras com 10% e 5% de prata, respectivamente. A atividade antimicrobiana das AgNps impregnadas em tecidos de algodao foi avaliada e apresentou resultados promissores na inibicao do crescimento bacteriano e fungico.