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Estudos cinéticos e fotoquímicos de compostos de Ru(II) com ligantes bipiridínicos e bifosfínicos de fórmula geral cis- [RuCl2(P-P)(N-N)] (P-P = bifosfinas e N-N N-heterocíclicos bidentados)
(Universidade Federal de São Carlos, 2010-10-14) Nascimento, Fábio Batista do; Batista, Alzir Azevedo; https://lattes.cnpq.br/6469642481998660; https://lattes.cnpq.br/8022643415351039
In this thesis it were studied substitution reactions in ruthenium complexes of the type cis-[RuCl2(P-P)(N-N)] and cis-[RuCl2(dppb)(N-O)] (P-P = dppm, dppe, dppp and dppb; N-N = bipy, Me-bipy, MeO-bipy, Cl-bipy and fen; N-O = 2-acpy, 2-bzpy and 2- dpk). For all complexes, in a period of 24 hours, there was only the substitution of a chloride (Cl-) coordinated to the metal. The ligands used in substitution reactions and kinetic studies were: py, 4-pic and coordenant solvents (CH3CN and PhCN). Only the Cl- trans positioned to P of diphosphines was labilized giving rise to the entering ligand, confirming the greater trans effect of phosphine ligands in relation to N-N and N-O. The mechanism attributed to substitution reactions was dissociative because the reactions do not show dependence of ligand entry. DFT calculations showed the effective participation of the Cl atom trans to the P atom of the diphosphines in the formation of the HOMO orbital. This fact shows that the reactivity of Cl atoms is different and they can be replaced selectively. Good linearity was observed for the percentage of participation of d orbitals of ruthenium in the formation of HOMO for the dissociation of Cl- complex indicating that the strength of the Ru-Cl- bond is due to the direct interaction of the orbitals of Cl- and the d orbitals of ruthenium. Exploratory studies using irradiation of light at fixed wavelengths were performed to study possible influence of the effect of the exchange rate of Cl- and also on the isomerization reaction trans/cis-[RuCl2(dppb)(bipy)]. An increase in the rate of exchange reaction was observed in the kinetics of substitution. In the isomerization processes were not observed. The substitution reactions of Cl- in the complexes cis- [RuCl2(dppb)(N-N)] (N-N = bipy and phen) by nitrile ligands (e.g. PhCN and CH3CN), lead to the formation of complexes in which trans ligands L were coordinated by the nitrogen atom of the ligands N-N in the final complex. However, studies of 31P{1H} NMR and cyclic voltammetry confirmed that the reactions take place initially with the replacement of L trans to P atom followed by an isomerization process. This is attributed to the strong competition of π between nitrile and phosphine ligands, and its final position is determined by this effect.
Aproveitamento do caroço do açaí como substrato para a produção de enzimas por fermentação em estado sólido
(Universidade Federal de São Carlos, 2010-10-14) Santos, Rodrigo Rafael Mendonça dos; Pessoa, José Dalton Cruz; https://lattes.cnpq.br/4212703554284544; https://lattes.cnpq.br/5649914970078519
The açaí agroindustry is the most important productive chains in northern Brazil. The residues in the marketing of açaí consists mainly of its pits, which are discarded in landfills and waterways without any treatment. A possible application to açaí pits is its use as substrate for solid state fermentation (SSF) for the production of lignocellulolytic enzymes as CMCase and xylanase, which act in the conversion of lignocellulosic materials into fermentable sugars. Currently, the cost of production of these enzymes has emerged as the biggest obstacle to the use of agro-industrial waste and the process of SSF gained prominence in this context due to several advantages over other technologies. The SSF process presents a large number of variables that affect the production of metabolites of interest, highlighting the sources of carbon and nitrogen, inducing growth and mineral salts. This study aimed to evaluate the use of pits of açaí as substrate for enzyme production by SSF evaluating the influence of the composition of culture medium for SSF through application of the methodology of statistical design full factorial 24 for selection of significant variables. The variables studied were the initial medium moisture and the concentrations of meat peptone extract, yeast extract, and CMC. After extraction of the enzyme complex and quantification of CMCase and xylanase activities, the variables of concentration of meat peptone extract and yeast extract were significant for enzyme production. Subsequently, a central composite rotatable design (CCRD) was made to achieve the optimization of the process parameters. The highest activities were obtained by increasing the concentration of meat peptone extract and yeast extract, reaching 8.24 U g-1 and 8.08 U g-1, to CMCase and xylanase, values, respectively. Additional tests were made at concentrations three times higher than those used at the midpoint of the CCRD, which indicated an increase of 1.59 and 1.16 times in the enzymatic activities of CMCase and xylanase, respectively. However, by Tukey test, these increases did not differ statistically in comparison to the tests results obtained using concentrations of reagents encoded at +1.41, giving economic advantage to the tests made with smaller amounts of reagents. The pit of açai has shown promising as a substrate for SSF, but additional studies are performed to define and optimize the process parameters.
Determinação simultânea de íons metálicos utilizando voltametria de redissolução anódica e métodos de calibração multivariada
(Universidade Federal de São Carlos, 2010-10-14) Marreto, Paola Daniele; Faria, Ronaldo Censi; https://lattes.cnpq.br/8659496864305621; https://lattes.cnpq.br/3608366417250207
This work describes the determination of Cu2+, Cd2+, Pb2+, Zn2+ and Co2+ using electroanalytical techniques and analyzing the data with chemometric tools. First, an univariate approach was used to investigate RMSEParately each ion using anodic stripping voltammetry in two different concentration range, mg L-1 and μg L-1. Then, the voltammetric profiles were measured for the mixture to check for interaction among them. In a second step, an orthogonal array with 16 experiments was used a calibration matrix and a second one with 10 samples as validation group. Then the profiles were mean centered and the PLS algorithm with different kind or data transformation were used to calculated both the cross validation and external validation. To improve the results KS and SPXY methods were also used. PLS results were the best method for the cross calibration detection but such procedure leaded only to correct measuring of 3 different ions. Following, the SPA method were used together with KS and SPXY and results shown the correct determination of 4 ions with external validation. A further improvement of the results were obtained when the SPA procedure were used together with MLR method to select the variables (potentials, in the present case). In this case, the prediction capacity increased and also the effect of variables selection and its correlation with the formation of intermetallic compounds were evaluated.