Synthesis of oligo(thienylenevinylenes) substituted with alkoxy groups

Abstract

Conjugated oligomers based on a combination of thiophene and 3,4-dialkoxythiophene moieties have been synthesized via the Vilsmeier formylation, Wittig-Honer reaction, and McMurry coupling reaction starting from dimethyl 3,4-dihydroxythioLinear p-conjugated molecular or polymeric systems are the focus of extensive current research interest for their opt-electronic properties and their potential applications in the field of opt-electronic devices, such as light-emitting diodes [1], field effect transistors [2,3], and nonlinear optics (NLO) [4,5]. More recently, their potential use as molecular wires in molecular electronics has attracted much attention [6]. Oligo(thiophenes) [7,8], oligo(thienylenevinylenes) [9][10][11][12], oligo(phenylenevinylene) [13][14][15][16] other related oligomers [17] possessing well-defined conjugated lengths and oligomers [17] possessing well-defined conjugated lengths and structures have been prepared in order to contribute to a better understanding of electronic materials. Roncali and his coworkers constructed extended thienylenevinylene oligomers using 3,4-dihexylthiophene as a building block and found that oligo(thienylenevinylenes) are the most efficient extended molecular wires among the known p-conjugated systems [9][10][11][12]. Long alkyl groups such as the hexyl group are required to improve the solubility of the higher oligomers and also serve as electron-donating groups to control the electronic properties of p-conjugated systems. In this article, we report a new type of oligo(thienylenevinylenes) consisted of a mixture of 3,4-dialkoxythiophene and thiophene rings. Since 3,4-dialkoxythiophenes are more electron rich than unsubstituted thiophenes, oligomers linked with such thiophene units are expected to show a narrow highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy gap. Furthermore, S • • • O intramolecular interaction may contribute to reduce the HOMO-LUMO energy gap. Fine tuning of the HOMO and LUMO energies of molecular wires is essential for efficient electron transport over a long distance [18,19]. Alkoxy derivatives have several advantages over the alkyl-substituted ones since alkoxy groups are more effective to raise the HOMO energy level than alkyl groups; the presence of alkoxy groups in place of alkyl substituents decreases the ionization potential of polymers and oligomers. Thus, if the oxygen is directly attached to the ring, the band gap (DE) of poly(thio-

Incorporation of Fused Tetrathiafulvalenes (TTFs) into Polythiophene Architectures: Varying the Electroactive Dominance of the TTF Species in Hybrid Systems

“…Photoluminescence and Photoinduced Absorption Spectra of Polymer 4. Thienylenevinylene-based oligomers − and polymers , have been studied in the past few years as promising candidates for low band gap materials. Optical absorption onsets <1.5 eV have been reported for such material systems .…”

Isolation and Crystal Structures of Two Singlet Bis(Triarylamine) Dications with Nonquinoidal Geometries

“…Compound 1 26 and Fe(C 5 H 4 Ac) 2 ·AgBF 4 were synthesized by literature procedures. Compound 2 was synthesized using the Horner reaction of p -(diarylmino)benzyl phosphonate and a thiophene dialdehyde in a fashion similar to a closely related compound described in ref (see Supporting Information for details). Other materials were obtained from commercial sources and used without further purification.…”

Economical and Environmentally Friendly Organic hydrazone Derivatives Characterized by a Heteroaromatic Core as Potential Hole Transporting Materials in Perovskite Solar Cells

“…In the end, the dialdehyde intermediate, as well as the dialdehyde of the 3‐4‐dibutoxythiophene, was submitted with the stoichiometric amount of acid to the final condensation with the proper hydrazine in THF at room temperature to give the corresponding product. Although the synthesis of 3‐4‐dibutoxythiophene‐2,5‐bisaldehyde was reported in literature by Ono et al., [18] we decided to develop a new synthetic protocol to reduce the cost of the final compounds that will be discussed later. In fact, using as starting material for the initial nucleophilic substitution reaction the 3,4‐dihydroxythiophene‐2,5‐dicarboxylic acid diethyl ester, instead of the dimethyl ester, the final cost had a 6‐fold reduction.…”

“…The crude product was immediately subdued to a reduction reaction performed with lithium aluminium hydride to obtain the corresponding alcohol. In the end, the dialdehyde intermediate was obtained after a mild oxidation of the dialcohol derivative performed with manganese (IV) oxide in chloroform, adapted from a literature procedure, [19] instead of the more expensive and complicated oxidation with tetrapropylammonium perruthenate (VII) and N-methylmorpholine N-oxide proposed by Ono et al [18] The final yields of the three-step synthetic protocols were around 55 % for the disubstituted hydrazones and around 40 % for the monosubstituted one. On the contrary, the overall yield achieved for the synthesis of Ph 2 -P-Ph 2 was around 30 % at the end of the four-step protocol, mainly due to the low yield of the initial alkylation reaction.…”