Investigation of the Photophysical and Electrochemical Properties of Alkoxy-Substituted Arylene−Ethynylene/Arylene−Vinylene Hybrid Polymers

Abstract

High-molecular-weight, soluble and thermostable alkoxy-substituted arylene−ethynylene/arylene−vinylene conjugated polymers, 13 and 14, have been successfully synthesized through the Horner−Wadsworth−Emmons olefination of luminophoric dialdehydes 7 and 9 and bisphosphonate 12 in very good yields. They were characterized through 1H NMR, 13C NMR, IR, and elemental analysis. The investigation of their photophysical and electrochemical properties has been carried out. Although almost identical absorption and emission spectra were obtained in dilute chloroform solution for all polymers 13, the full width at half-maximum (fwhm) value of the emission curves depends on the length of the attached side chains. The presence of anthracenylene units in 14 leads to a red shift of its absorption and emission spectra relative to 13. Strong self-reabsorption after excitation in solution was observed for this polymer. The solid-state photophysical properties of 13 and 14 (photoconductivity, absorption and emission spectra, fluorescence quantum yield, Stokes shift, and fwhm) greatly depend on the nature (linear or branched), length, and location of the grafted alkoxy side groups. Photoconductivity is easily detected in polymers having octadecyloxy chains (13aa, 13ab, 14). Long linear (octadecyl, i.e., 13aa) or short branched (2-ethylhexyl, i.e., 13 cc) side chains at position R2 (phenylene−vinylene segment) are necessary to obtain sharp and well-resolved emission spectra accompanied by high fluorescence quantum yields. The quasi-donor (phenylene−vinylene segment)−acceptor (arylene−ethynylene segment) nature of these polymers could explain the great discrepancy between the electrochemical band gap energy, E g ec ≈ 1.60 eV, as obtained from the onset values of the redox potentials in cyclic voltammetry and in differential pulse polarography measurements, and the optical band gap energy, E g opt ≈ 2.30 eV, from the absorption spectra.

From Byproducts to Efficient Fluorophores: A Route to the Synthesis of Fluorubines

“…We estimated the optical band gap (E opt g ) of this molecule by two methods, namely the socalled 10 % method (E opt g, 10% ; of the absorption maxima at the lower-energy site), which was introduced by Hçrhold and the commonly used tangential through the turning point method (E opt g, T ). [11] Both methods delivered nearly similar results, but we would like to mention that the 10 % method is still easier in its handling. However, as listed in Table 1 we found an optical band gap of approximated 2.19 eV for 3 a.…”

Poly(anthrylenebutadiynylene)s: Precursor‐Based Synthesis and Band‐Gap Tuning

“…[4] Significant advances include the preparation of poly(9,10-anthrylene)s, [5] poly(9,10-anthrylenevinylene)s, [6] and poly(9,10-anthryleneethynylene)s. [7] Despite their interesting properties, these materials display moderate band gaps (greater than 2.0 eV), which are a consequence of the sterically hindered nature of the 9-and 10-positions of the anthryl group. Müllen and coworkers have demonstrated that poly(9,10-anthrylene)s and oligo(9,10-anthrylenevinylene)s adopt twisted conformations, and this same group has shown that a substantial lowering of the band gap is effected by enforcing a coplanar conformation in ladder poly(p-phenylene-alt-9,10-anthrylene)s. [8] We became interested in the possibility that poly(anthrylenebutadiynylene)s (PABs) could exhibit substantial delocalization owing to the ability of the butadiyne functional group to allow a coplanar arrangement of adjacent repeat units or arising from the rotationally symmetric nature of its electronic structure.…”

Synthesis of Random Copolymers of 2,6-Di(thiophen-2-Yl)aniline and 2,2'-(Thiophen-2,5-Diyl)dianiline With Aniline and Its Evaluation in Organic Solar Cells

“…The obtained wavelength divides the constant 1242 (Eg = hc/l), giving an estimate bandgap value in eV [13][14]28]. According to the data shown in Fig.…”