Star-Shaped Polycyclic Aromatics Based on Oligothiophene-Functionalized Truxene:  Synthesis, Properties, and Facile Emissive Wavelength Tuning

Abstract

A facile approach to soluble star-shaped oligothiophene-functionalized polycyclic aromatics based on truxene is developed in this Communication. The Suzuki coupling reactions afford the thiophene-containing polycyclic aromatics with long branches (about 2.1 nm length from the heart to the periphery) from truxene precursor with excellent yields. The unsubstituted alpha-positions of thiophene rings allow for efficient halogenation and for further functionalization. The investigation of proton NMR spectra indicates that the hexahexyl groups efficiently prevent the self-association through the arene-arene pi-stacking. Chemical shifts belonging to methylene groups move more upfield than do those of methyl groups. These chemical shift values (about 0.5-0.6 ppm) are quite lower than those of normal methyl and methylene groups. We also prepare a dendritic hyperbranched polymer P1 through FeCl3 mediated oxidative polymerizations. The photophysical properties of all compounds possessing good symmetry are investigated by UV-vis and emission measurement.

Solution‐Processed Bulk Heterojunction Photovoltaic Cells from Gradient π‐Conjugated Thienylene Vinylene Dendrimers

“…G0-2-1, Tr(TV) 2 Tr, and Tr(TV) 4 Tr exhibit a peak at about 341 nm owing to the same peripheral moiety, namely, the monothiophene-functionalized truxene chromophore. [15] For G0-4-2, the absorption in the short wavelength range peaked at about 414 nm, which was assigned to the (TV) 2 -functionalized truxene unit. The dendrimers exhibited another absorption peak at 446 nm for G0-2-1, and at 501 nm for G0-4-2.…”

“…Reduction of 1 [15] with NaBH 4 afforded compound 2 in 94 % yield. Previously, we observed that the target bromide obtained by reaction of alcohol 2 with PBr 3 decomposed readily.…”

“…[17] Dendrimer G0-2-1 was obtained in 64 % yield through a threefold WittigHorner reaction between trialdehyde 4 [15] and phosphonate 3. [18] Reduction of (E)-5-(2-(thiophen-2-yl)vinyl)thiophene-2-carbaldehyde with NaBH 4 gave 5 in 97 % yield.…”

“…The introduction of hexyl groups in the terminal thiophene ring greatly improved the solubility of the final product. The Wittig-Horner reaction between 9 [15] and diethyl(5-hexylthiophen-2-yl)methylphosphonate [21] afforded 10 in 83 % yield. Compound 10 was converted into monoaldehyde 11 in 83 % yield by treatment with nBuLi and anhydrous DMF.…”

“…To better understand the photophysical properties of the newly synthesized gradient p-conjugated dendrimers, compounds Tr(TV) 2 Tr [15] and Tr(TV) 4 Tr (Tr = truxene; TV = thienylene vinylene) were prepared as the linear models of dendrimers G0-2-1 and G0-4-2. Tr(TV) 4 Tr was synthesized by Wittig-Homer reaction between (E)-5,5'-(ethene-1,2-diyl)dithiophene-2-carbaldehyde and 3 in 71 % yield.…”