A. Maurício C. Fonseca

Push-Pull Tricyanovinyl-Substituted Thienylpyrroles: Synthesis, Solvatochromic and Electrochemical Properties

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.

Quantum Chemical DFT and Spectroscopic UV-Vis-NIR Analysis of a Series of Push-Pull Oligothiophenes End-Capped by Amino/Cyanovinyl Groups

A series of push-pull chromophores built around thiophene-based π-conjugating spacers and bearing various types of amino-donors and cyanovinyl-acceptors have been analyzed by means of UV-Vis-NIR spectroscopic measurements. Density functional theory (DFT) calculations have also been performed to help the assignment of the most relevant electronic features and to derive useful information about the molecular structure of these NLO-phores. The effects of the donor/acceptor substitution in the electronic and molecular properties of the π -conjugated spacer have been addressed. The effectiveness of the intramolecular charge transfer (ICT) has also been tested as a function of the nature of the end groups (i.e., electron-donating or electron-withdrawing capabilities).

Synthesis and evaluation of NLO properties of π-conjugated donor‐acceptor systems bearing pyrrole and thiophene heterocycles

Two series of novel push-pull heterocyclic azo dyes have been synthesized and characterized. The two series of compounds were based on different combinations of π-conjugated bridges (bithiophene and thienylpyrrole) which also act simultaneously as donor groups, together with diazo(benzo)thiazolyl as acceptor moieties. Their thermal stability and electrochemical behavior were characterized, while hyper-Rayleigh scattering (HRS) was employed to evaluate their second-order nonlinear optical properties. The results of these studies have been critically analyzed together with several thienylpyrrole azo dyes reported earlier from our laboratories in which the thienylpyrrole system was used as the donor group functionalized with aryl and (benzo)thiazolyldiazene as acceptor moiety. The measured molecular first hyperpolarizabilities and the observed linear optical and redox behavior showed strong variations in function of the heterocyclic spacers used (bithiophene or thienylpyrrole) and were also sensitive to the acceptor strength of the diazenehetero(aryl) moiety.

Highly efficient and thermally stable NLO organic materials based on pyrrole and thiophene heterocycles

A series of novel donor-acceptor chromophores designed to have good second order nonlinear optical responses has been synthesized and characterized. This series of compounds was designed to explore the consequence of using different electron accepting moieties which were linked through an arylthiophene bridge to a pyrrole heterocycle that plays the role of an auxiliary donor group. These new push-pull chromophores have been extensively characterized using cyclic voltammetry, thermogravimetric analysis and hyper-Rayleigh scattering (HRS) in solution. The measured molecular first hyperpolarizabilities and the observed electrochemical behavior showed that they were very sensitive to the acceptor strength of the acceptor moieties. Moreover, the combination of their good nonlinearity and high thermal stability make them good candidates for potential device applications.