Selectivity of hexaphenylbenzene-based hydrocarbon stationary phase with propeller-like conformation for aromatic and aliphatic isomers.

Herein we report a propeller-like hexaphenylbenzene-based hydrocarbon material (denoted as BT) as the stationary phase for capillary gas chromatography (GC). The statically-coated BT capillary column showed a high column efficiency of 4340 plates m-1 and weak polarity. Owing to its unique conformation, π-electron toroidal delocalization and intrinsic microporosity, the BT stationary phase exhibited interesting selectivity for aromatic compounds over alkanes. Compared with the graphene (G) column, the BT column showed much prolonged retention and high selectivity for aromatic isomers, especially methylnaphthalenes, dimethylnaphthalenes and phenanthrene/anthracene, mainly because of its propeller-like conformation with rich intercalation effects. Moreover, it exhibited good column repeatability (intra-day, inter-day) and reproducibility (between-column) with RSD values on the retention times less than 0.08% for intra-day, 0.32% for inter-day and 3.8% for between-column, respectively. Also, it showed good potential for determination of minor isomer impurities in real samples. To the best of our knowledge, this work presents the first example of employing an neat aromatic hydrocarbon material as the GC stationary phase with high selectivity for analytes of a wide ranging polarity.

Series of Multifluorine Substituted Oligomers for Organic Solar Cells with Efficiency over 9% and Fill Factor of 0.77 by Combination Thermal and Solvent Vapor Annealing.

We report the synthesis of a family of multifluorine substituted oligomers and the corresponding polymer that have the same backbones but different conjugation lengths and amounts of fluorine atoms on the backbone. The physical properties and photovoltaic performances of these materials were systematically investigated using optical absorption, charge mobility, atomic force microscopy, transmission electron microscopy, grazing incidence X-ray diffraction, resonant soft X-ray scattering methods, and photovoltaic devices. The power conversion efficiencies (PCEs) based on oligomers were much higher than that in the polymer. Moreover, the devices based on BIT6F and BIT10F, which have an axisymmetric electron-deficient difluorobenzothiadiazole as the central unit, gave slightly higher PCEs than those with centrosymmetric electron-rich indacenodithiophene (IDT) as the central unit (BIT4F or BIT8F). Using proper solvent vapor annealing (SVA), particularly using thermal annealing (TA) followed by SVA, the device performance could be significantly improved. Notably, the best PCE of 9.1% with a very high FF of 0.76 was achieved using the medium-sized oligomer BIT6F with the optimized film morphology. This efficiency is the highest value reported for organic solar cells from small-molecules without rhodanine terminal group. More excitingly, devices from the shortest oligomer BIT4F showed an impressively high FF of 0.77 (the highest FF value reported for solution-processed small-molecule organic solar cells). These results indicate that photovoltaic performances of oligomers can be modulated through successive change in chain-length and fluorine atoms, alternating spatial symmetric core, and combined post-treatments.

Rational design of asymmetric red fluorescent probes for live cell imaging with high AIE effects and large two-photon absorption cross sections using tunable terminal groups.

In this work, we report the synthesis of a family of donor-acceptor (D-A) π-conjugated aggregation-induced red emission materials (TPABT, DTPABT, TPEBT and DTPEBT) with the same core 2,2-(2,2-diphenylethene-1,1-diyl)dithiophene (DPDT) and different amounts and different strengths of electron-donating terminal moieties. Interestingly, TPABT and TPEBT, which have asymmetric structures, give obviously higher solid fluorescence quantum efficiencies in comparison with those of the corresponding symmetric structures, DTPABT and DTPEBT, respectively. In particular, the thin film of TPEBT exhibited the highest fluorescence quantum efficiency of ca. 38% with the highest αAIE. Moreover, TPEBT and DTPEBT with TPE groups showed two-photon absorption cross-sections of (δ) 1.75 × 103 GM and 1.94 × 103 GM at 780 nm, respectively, which are obviously higher than the other two red fluorescent materials with triphenylamine groups. Then, the one-photon and two-photon fluorescence imaging of MCF-7 breast cancer cells and Hela cells, and cytotoxicity experiments, were carried out with these red fluorescent materials. Intense intracellular red fluorescence was observed for all the molecules using one-photon excitation and for TPABT using two-photon excitation in the cell cytoplasm. Finally, TPEBT is biocompatible and functions well in mouse brain blood vascular visualization. It is indicated that these materials can be used as a specific stain fluorescent probe for live cell imaging.

Hexaphenylbenzene-Based, π-Conjugated Snowflake-Shaped Luminophores: Tunable Aggregation-Induced Emission Effect and Piezofluorochromism.

In this work, two rigid, multiple tetraphenylethene (TPE)-substituted, π-conjugated, snowflake-shaped luminophores BT and BPT were facilely synthesized by using a 6-fold Suzuki coupling reaction. These molecules are constructed based on the nonplanar structure of propeller-shaped hexaphenylbenzene (HPB) or benzene as core groups and TPE as end groups. As a result, they reserve the intrinsic aggregation-induced emission (AIE) property of the TPE moiety. Meanwhile, both fluorescence quantum yield and piezochromic behavior in the solid state can be tuned or switched by inserting the phenyl bridges through changing the twisting conformation. The more extended structure BPT showed a much stronger AIE effect and higher ΦF,f in the solid state in comparison with that of BT. Furthermore, an excellent optical waveguide application of these molecules was achieved. However, the revisable piezofluorochromic behavior has only appeared when BT was ground using a pestle and treated with solvent.

Aggregation-induced emission and efficient solid-state fluorescence from tetraphenylethene-based N,C-chelate four-coordinate organoborons.

In it together: Thermally stable N,C-chelate four-coordinate organoborons were attained by grafting intramolecular B⋅ ⋅ ⋅N coordination into tetraphenylethene-pyridine and -quinoline adducts. They exhibit aggregation-induced emission characteristics (see figure), and high fluorescence quantum yields approaching unity in solid films.

From tetraphenylethene to tetranaphthylethene: structural evolution in AIE luminogen continues.

Replacement of phenyl ring(s) in tetraphenylethene by naphthalene ring(s) generates a series of new luminogens with aggregation-induced emission (AIE) characteristics, demonstrating that bulky naphthalene rings can serve as a rotor to construct AIE luminogens.

Efficient electroluminescence from excimers of 1,3,6,8-tetrakis(3,5-dimethylphenyl)pyrene.

Excimers are generally considered as detrimental to OLEDs. For pyrene-based chromophores, however, this is not always true. In this contribution, two new methylated tetraphenylpyrenes, 1,3,6,8-tetra-o-tolylpyrene (TTPy) and 1,3,6,8-tetrakis(3,5-dimethylphenyl)pyrene (TDMPPy), were synthesized through Suzuki coupling reactions. TDMPPy absorbs and emits light at longer wavelengths than TTPy due to its more planar conformation and thus better conjugation. TDMPPy is prone to excimer formation, thus leading to a strong bathochromic shift (84 nm) in the photoluminescence spectrum of its film. TDMPPy exhibits efficient electroluminescence originating from pyrene excimers, affording a maximum luminance of 26,670 cd m(-2) and a current efficiency as high as 10.8 cd A(-1) in a non-doped OLED (ITO/PEDOT:PSS (50 nm)/NPB (30 nm)/TDMPPy (30 nm)/TPBI (40 nm)/Ca:Ag).

Aggregation-enhanced emission and efficient electroluminescence of tetraphenylethene-cored luminogens.

A new design of luminescent materials by decorating a tetraphenylethene core with four aromatic chromophores is proposed. The generated luminogens exhibit aggregation-enhanced emission and excellent solid-state fluorescence efficiency (93-99%). Efficient non-doped OLEDs based on them afford remarkable efficiencies up to 11 cd A(-1).

A fully substituted 3-silolene functions as promising building block for hyperbranched poly(silylenevinylene).

A 3-silolene derivative, 2,2,5,5-tetrakis(dimethylsilyl)-1,1-dimethyl-3,4-diphenyl-3-silolene (TDMSHS), is first synthesized and characterized by X-ray diffraction crystallography and spectroscopic methods. Hydrosilylation polymerization of TDMSHS with 1,1-dimethyl-2,5-bis(4-ethynylphenyl)-3,4-diphenylsilole in the presence of Karstedt's catalyst generates a stereoregular silole-containing hyperbranched poly(silylenevinylene) (hb-SPSV) with a high molecular weight (M(w) = 146,000, M(w)/M(n) = 1.5) in high yield (≈95%). hb-SPSV exhibits excellent thermal stability and strong fluorescence, and the emission of its aggregates in aqueous mixture can be quenched efficiently by picric acid with large quenching constants K(SV) up to 414400 M(-1).