An evaluation of the chalcogen atom effect on the mesomorphic and electronic properties in a new homologous series of chalcogeno esters

Abstract

Uma série de calcogeno ésteres, 1a, 6a e 6b foi obtida em uma rota sintética conveniente. A análise de microscopia óptica de luz polarizada (POM) e calorimetria diferencial de varredura (DSC) mostrou que estes calcogeno ésteres apresentam uma ampla faixa de mesofase nemática. Além disso, espectros de absorção na região do UV-Vis em solução (ca.10 -5 mol L -1 ) também foram obtidos de maneira a se obter a diferença de energia entre os orbitais moleculares HOMO-LUMO, para posterior comparação com os resultados teóricos. Os valores calculados para o gap de HOMO-LUMO estão de acordo com os valores experimentais obtidos, onde a eletronegatividade do heteroátomo (O, S e Se) deve ser o principal fator para a localização do máximo de absorção. Um estudo teórico foi realizado utilizando cálculos de DFT/B3LYP com método híbrido de Becke aplicando uma correlação funcional de Lee-Yang-Parr (B3LYP) com a base DGDZVP a fim de avaliar algumas propriedades físico-químicas relacionadas com o mesomorfismo e as propriedades eletrônicas espectrais. Através da síntese destes compostos, a influência do átomo de calcogênio nas propriedades fotofísicas e mesomórficas pôde ser avaliada de uma forma mais precisa.A series of chalcogeno esters 1a, 6a and 6b have been synthesized in a straightforward manner. Polarized-light optical microscopy (POM) and differential scanning calorimetry (DSC) showed that these chalcogeno esters displayed a wide nematic range of mesophase. In addition, UV-Vis in solution (ca.10 -5 mol L -1 ) was applied in order to obtain the HOMO-LUMO gap for further comparison with the theoretical results. The calculated values to the HOMO-LUMO gap are in excellent agreement with the experimental results, where the electronegativity of the heteroatom (O, S and Se) seems to play a fundamental role in the absorption maxima location. A theoretical study was performed using a DFT/B3LYP calculations with Becke's three-parameter hybrid method applying the Lee-Yang-Parr functional correlation (B3LYP) with DGDZVP basis set in order to evaluate some physical chemistry data related with mesomorphic and spectral eletronic properties. By synthesizing these compounds we were able to get a more precise description about the influence of the chalcogen atom on the mesomorphic and photophysical properties. Rampon et al. 2101 Vol. 21, No. 11, 2010 The biological and medicinal properties of selenium and organoselenium compounds are increasingly appreciated, mainly due to their antioxidant, antitumor, antimicrobial and antiviral properties. 4 Besides, the synthesis of peptides containing selenocysteine is rapidly gaining interest with the discovery of an increasing number of proteins containing this aminoacid. Keywords 5Chalcogeno esters (thiol, selenol and tellurol esters) are useful synthetic intermediates that have been employed, for example, as acylating reagents, building blocks for heterocyclic compounds, precursors of acyl radicals and anions, as well asymmetric aldol reactions. However, rare are the examples where these compounds a...

Evaluation of Se-phenyl-thiazolidine-4-carboselenoate protective activity against oxidative and behavioral stress in the maniac model induced by ouabain in male rats

“…1) was synthesized according to a previously published method [18]. Analysis of the 1 H NMR and 13 C NMR spectra were in full agreement with its assigned structure.…”

Atom Efficient Preparation of Zinc Selenates for the Synthesis of Selenol Esters under “On Water” Conditions

“…Aromatic selenol esters, such as I , are stable liquid crystals with a large nematic mesophase range [2,3,4]. In contrast to their sulfur analogues, selenol esters only recently have attracted the attention to their pharmacological potential; the thiazolidine-4-carboselenoate II is a potent antioxidant [5], while the polyfunctionalized selenol esters III and IV presented high cytotoxic and antiproliferative activities against MCF-7 human cancer cells [6,7] (Figure 1).…”

“…As a consequence of the increasing demand for selenol esters, the number of methods to prepare this class of compounds has been increased along the years [1,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43] Among the strategies to prepare selenol esters there are the reactions of nucleophilic selenium reagents with an acyl group source, such as N -acyl benzotriazoles [17,18] activated carboxylic acids (using DCC [3] or PBu 3 [4,5,19,20]), enol esters [21], anhydrides [22,23,24], esters [25], carbon monoxide [26,27], aldehydes [28,29] or acyl chlorides [2,7,30,31,32,33,34,35,36,37,38,39,40,41,42,43]. Other approaches to selenol esters involve the alkylation of selenocarboxylate anions with alkyl h...…”

Synthesis of Functionalized Organoselenium Materials: Selenides and Diselenides Containing Cholesterol

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