Synthesis and Properties of Monodisperse Oligofluorene-Functionalized Truxenes:  Highly Fluorescent Star-Shaped Architectures

Abstract

This paper describes the strategy toward novel monodisperse, well-defined, star-shaped oligofluorenes with a central truxene core and from monofluorene to quaterfluorene arms. Introduction of solubilizing n-hexyl groups at both fluorene and truxene moieties results in highly soluble, intrinsically two-dimensional nanosized macromolecules T1-T4. The radius for the largest oligomer of ca. 3.9 nm represents one of the largest known star-shaped conjugated systems. Cyclic voltammetry experiments reveal reversible or quasi-reversible oxidation and reduction processes (Eox = +0.74 to 0.80 V, Ered = -2.66 to 2.80 eV vs Fc/Fc+), demonstrating excellent electrochemical stability toward both p- and n-doping, while the band gaps of the oligomers are quite high (EgCV = 3.20-3.40 eV). Close band gaps of 3.05-3.29 eV have been estimated from the electron absorption spectra. These star-shaped macromolecules demonstrate good thermal stability (up to 400-420 degrees C) and improved glass transition temperatures with an increase in length of the oligofluorene arms (from Tg = 63 degrees C for T1 to 116 degrees C for T4) and show very efficient blue photoluminescence (lambdaPL = 398-422 nm) in both solution (PhiPL = 70-86%) and solid state (PhiPL = 43-60%). Spectroelectrochemical experiments reveal that compounds T1-T4 are stable electrochromic systems which change their color reversibly from colorless in the neutral state (approximately 340-400 nm) to colored (from red to purple color; approximately 500-600 nm) in the oxidized state.

Preparation of poly(fluorene)s using trans‐bis(dicyclohexylamine)palladium diacetate as a catalyst: Scope and limitations

“…Although the signal at 7.55-7.45 ppm is an expected one and can be easily assigned to the two protons in the ortho position to a bromo end group (cf. Scheme 1, R 1 or R 2 ¼ Br), 49 the signals at 7.40-7.30 and 6.88-6.80 ppm are unexpected. The first unanticipated signal can be assigned to three protons of a hydrogen-terminated PF6 (cf.…”

“…The first unanticipated signal can be assigned to three protons of a hydrogen-terminated PF6 (cf. Scheme 1, R 1 or R 2 ¼ H), 49 and the second can be assigned to two protons of PF6 featuring a hydroxy end group (cf. Scheme 1, R 1 or R 2 ¼ OH).…”

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

“…Figure 1 shows the MALDI-TOF MS spectrum of G0-4-2, in which the sharp molecular ion peak at m/z = 6246 Da (calcd: m/z = 6250 Da) and another signal corresponding to dehexylated fragment [MÀC 6 H 13 ] + (calcd: m/z = 6165 Da, found: m/z = 6161 Da) was clearly observed, which was similar to those of other truxene derivates. [22] All these results clearly indicated the molecular identity and purity of G0-4-2. The thermal properties of our dendrimers were analyzed by thermal gravimetric analysis (TGA).…”

“…[26] This result shows that the highly fluorescent truxene moieties in the dendritic structure effectively influence the optical properties of the OTV segments. [22] The improved fluorescence quantum yields are beneficial to photoinduced electron transfer efficiency in organic solar cells, in which the donor material was mixed with fullerene derivatives. [27] Thus, our design strategy might provide a general strategy to improve the performance of organic solar cells based on OTVs and other nonluminescent molecules.…”

Location, Location, Location ‐ Strategic Positioning of 2,1,3‐Benzothiadiazole Units within Trigonal Quaterfluorene‐Truxene Star‐Shaped Structures

“…We found that a modifi ed Suzuki protocol using Ba(OH) 2 as a base gave almost quantitative yields for T1Si-T4Si . To increase the yield of the oligofl uorene-truxene core compounds T1Si-T4Si in both Suzuki and Negishi coupling protocols, it was essential to increase the equivalents of the precursor arms (boronic acid or organozinc compound) relative to the core compound 2 or T2Br to a ratio of 5: 1 (instead of the 3.45: 1 ratio that was used in our original publication [ 6 ] ).…”