Papers by Author: António Maurício C. Fonseca

Abstract: CoPAN complex has been entrapped in the supercages of Y zeolite and the redox properties of this zeolite-encapsulated complex were investigated by cyclic voltammetry with a new method for the preparation of carbon toray-zeolite-modified electrode. Formation of the CoPAN complex was ascertained by surface analysis (SEM, XRD), chemical analysis (CA), spectroscopy methods (FTIR and UV/vis) and cyclic voltammetry in aqueous medium with zeolite-modified electrodes. The cyclic voltammetry studies obtained with a zeolite-modified electrode shows evidence for electroactivity restricted to boundary associated CoPAN complex.

Abstract: The encapsulation of Cu(II) purine derivative complex was carried out by ion exchange of the complex from aqueous solutions into zeolite NaY. The entrapped complex was characterized by spectroscopic methods (FTIR and ICP-AES) and surface analysis (XRD). The various techniques of characterization used show that the Cu(II) complex was effectively encapsulated in the zeolite and this process does not modify the morphology and structure of the NaY zeolite. These materials have potential applications in heterogeneous catalysis in mild reaction conditions.

Abstract: A hydride tungsten complex, [WH2(η2-OOCCH3)(Ph2PCH2CH2PPh2)2][BPh4], was entrapped in the interlayer of a pillared layered clay (PILC) and in NaY zeolite. The adsorption of the complex in the liquid phase was the immobilization process used. The free complex and the new materials were characterized by several techniques: structural analysis by DRX, nitrogen adsorption isotherms and spectroscopic methods (ICP-AES, FTIR and UV/Vis). Analysis of the data indicates that the tungsten(IV) complex is immobilized in the host microporous structures, and exhibit structural properties that are different from those of the free complex. These differences could arise either from distortions caused by steric effects imposed by the structures or from interactions with the host matrix.

Abstract: The synthesis of thienyl- substituted pyrrole azo dyes and their UV-visible, solvatochromic and electrochemical properties are described. In agreement with the solvatochromic data and also with the electrochemical study the new donor-acceptor systems synthesized could have applications in NLO.

Abstract: New tricyanovinyl- derivatives 1 of 1-(alkyl)aryl-2-(2´-thienyl)pyrroles 2 have been synthesized and characterized. Compounds 1 display dramatic reductions in both their optical and electrochemical band gaps in comparison to thienylpyrroles 2. The solvatochomic behavior of tricyanovinyl- derivatives 1 was investigated in a variety of solvents. In agreement with the solvatochromic and the electrochemical studies for push-pull derivatives 1 the new compounds prepared, can find application for manufacturing new materials with notable non-linear optical properties.