Papers by Keyword: Chromophores

Abstract: Two group chromophores with strong methoxy electron donor and CF₃ electron acceptor were synthesized and reported. To investigate the effects of conjugative bond and its length between electron donor and acceptor on optical properties, thiophene ring was incorporated into the conjugated units of group B compared to group A. The results showed that the incorporation of thiophene rings could significantly enhance molecular first hyperpolarizability and permit a high thermal stability. It has been found that molecular first hyperpolarizability increased continually by the increase of bond length of group A. However, further increase of conjugated bond length between electron donor and acceptor in group B reduced the molecular hyperpolarizability. This study indicates that both the nature of the conjugative bridge and its bond length between electron donor and acceptor have inner correlation to optimize the molecular hyperpolarizability for electro-optical applications.

Abstract: A series of optical polymeres were prepared by a Mitsunobu reaction from the corresponding N,N-dihydroxyethyl D-π-A chromophores and bisphenol A, which is new main-chain copolymeres with good solubility in ordinary organic solvents. The linear and nonlinear optical (NLO) properties were investigated by UV spectra and NLO measurements. The results indicate that the films of copolymeres exhibit a higher macroscopic second nonlinear optical coefficient, thermal stability and good optical transparency.

Abstract: Polydiacetylenes are a type of highly conjugated polymers, and highly polar species are obtained when these polymers contain donor-acceptor azobenzene entities. In this paper the synthesis, characterization and evaluation of the dielectric constant of two polydiacetylenes containing azobenzenes as pendant groups are discussed. The Azobenzene chromophores are covalently bonded to the main chain, and their polarity is defined by an electro-donor (amine) and an electro-acceptor group (nitro or chlorine) bonded to the ends of a conjugated azobenzene structure. Both polymers were processed into plates of 1cm diameter x 0.674 mm thickness using a thermo mechanic technique. Their dielectric constants were evaluated respect to the temperature in a range of frequency of 110 MHz-1.32 GHz, from room temperature to close to their respective T_g. The dielectric constant for the polymer containing the nitro group was higher than it for polymer containing the chloride atom at all temperatures. It is discussed in terms of the ability to nitro and chloride to attract electronic density.

Abstract: New push-pull thiobarbituric (oligo)thiophene derivatives 1 were synthesized, in good to excellent yields (60-98%), through Knoevenagel condensation of the corresponding formyl-(oligo)thiophenes 2 with 1,3-diethylthiobarbituric acid in dichloromethane, under basic conditions. Evaluation of the thermal and solvatochromic properties of these compounds was carried out and their NLO response was estimated. The values obtained suggest that these (oligo)thiophenes have good potential to be used as novel NLO materials.

Abstract: Thienyl- and bithienyl-1,3-benzothiazoles 1 and 2 were synthesised by reacting various formyl thienyl and bithienyl derivatives with o-aminobenzenethiol in moderate to excellent yields. Evaluation of the solvatochromic and fluorescence properties of these compounds was carried out. Due to their strong fluorescence and also the strong push-pull character, benzothiazole derivatives 1 and 2 can be used as potential NLO materials or as fluorescent markers.

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.