Synthesis, optical and electrochemical properties of a series of push-pull dyes based on the 4,4-bis(4-methoxy phenyl)butadienyl donor

Abstract

A series of twelve dyes based on the 4,4-bis(4-methoxyphenyl)butadienyl donor and differing by the electron acceptors have been designed and synthesized. The different dyes were characterized by UV-visible absorption spectroscopy as well as cyclic voltammetry. By fine tuning the electron-accepting ability of the fourteen selected acceptors, dyes absorbing between 400 and 650 nm could be obtained with this π-extended donor. To get a deeper insight into the optical properties, solvatochromism was investigated in 23 different solvents and remarkable linear correlations could be obtained using the Taft and Catalan solvatochromism scales. A comparison with four dyes used as reference compounds and differing from the series of twelve dyes by the structure of the electron-donating groups was also established so that the electron releasing ability of the 4,4-bis(4-methoxyphenyl)butadienyl donor could be compared with the reference ones. To prepare these four references compounds, only two electron acceptors previously used for the design of the twelve dyes have been employed. Interestingly, variation of the absorption maxima of the twelve dyes was determined as being more influenced by the polarizability of the solvent rather than by its polarity. To support the experimental results, theoretical calculations were carried out.

One-Pot Synthesis of Push–Pull Butadienes from 1,3-Diethyl-2-thiobarbituric Acid and Propargylic Alcohols

“…In this way, a simple decantation and consecutive washing with water, methanol and diethyl ether delivered 3a,b in pure form. The recorded IR, NMR ( 1 H and 13 C{ 1 H}) and HRMS spectra were in full agreement with the characterization data reported by Dumur and co-workers (full details are given in the Materials and Methods section and copies of the spectra included in the Supplementary Materials) [10,11]. The synthetic utility of this MW-assisted InCl3-catalyzed process was further demonstrated with the preparation of the novel butadiene 5-(3,3-bi([1,1'-biphenyl]-4yl)allylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione 3c starting from stoichiometric amounts of 1,3-diethyl-2-thiobarbituric acid 1 and 1,1-di([1,1'-biphenyl]-4yl)prop-2-yn-1-ol 4c (Scheme 5).…”

“…In this way, a simple decantation and consecutive washing with water, methanol and diethyl ether delivered 3a,b in pure form. The recorded IR, NMR ( 1 H and 13 C{ 1 H}) and HRMS spectra were in full agreement with the characterization data reported by Dumur and co-workers (full details are given in the Materials and Methods section and copies of the spectra included in the Supplementary Materials) [10,11].…”

“…In this context, the pseudoaromatic 2-thioxodihydropyrimidine-4,6(1H,5H)-dione ring of thiobarbituric acid and its N-alkylated derivatives has been extensively employed as an electronwithdrawing moiety in push-pull chromophores [6][7][8][9]. Representative examples are dyes 3a,b, recently described by Dumur and co-workers, featuring p-methoxyphenyl and pdimethylaminophenyl donor groups connected to the barbituric acid skeleton through a 1,3-butadiene chain spacer (Scheme 1), which showed a marked solvatochromic behavior in solution [10,11]. As shown in Scheme 1, compounds 3a,b were obtained by Knoevenagel condensation of commercially available 1,3-diethyl-2-thiobarbituric acid 1 with the corresponding α,β-unsaturated aldehyde 2a,b in refluxing ethanol under basic conditions.…”

“…As shown in Scheme 1, compounds 3a,b were obtained by Knoevenagel condensation of commercially available 1,3-diethyl-2-thiobarbituric acid 1 with the corresponding α,β-unsaturated aldehyde 2a,b in refluxing ethanol under basic conditions. For the preparation of enals 2a,b, Dumur and co-workers followed a classical synthetic behavior in solution [10,11]. As shown in Scheme 1, compounds 3a,b were obtained by Knoevenagel condensation of commercially available 1,3-diethyl-2-thiobarbituric acid 1 with the corresponding α,β-unsaturated aldehyde 2a,b in refluxing ethanol under basic conditions.…”

“…behavior in solution [10,11]. As shown in Scheme 1, compounds 3a,b were obtained by Knoevenagel condensation of commercially available 1,3-diethyl-2-thiobarbituric acid 1 with the corresponding α,β-unsaturated aldehyde 2a,b in refluxing ethanol under basic conditions.…”