Tuning Dipole Orientation of 2,6-Azulene Units in Conjugated Copolymers by C-H Activation Strategy toward High-Performance Organic Semiconductor.

Azulene has aroused widespread interest for constructing optoelectronic materials. However, controlling the dipole orientation of 2,6-azulene units in the conjugated polymer backbone is a significant challenge so far. Herein, by C-H activation strategy, three 2,6-azulene-TPD-based conjugated copolymers with different dipole arrangements were synthesized, where TPD = thieno[3,4-c]pyrrole-4,6-dione. The dipole arrangements of 2,6-azulene units were random for P(AzTPD-1), head-to-head/tail-to-tail for P(AzTPD-2), and head-to-tail for P(AzTPD-3). These polymers exhibited unipolar n-type semiconductor characteristics in organic field effect transistors. Moreover, regioregular polymer P(AzTPD-3) displayed the best device performance with an electron mobility of up to 0.33 cm2 V-1 s-1, which makes P(AzTPD-3) a high-performance n-type polymeric semiconductor. These results demonstrate that incorporation of 2,6-azulene units into the polymeric backbone together with the regulation of the dipole orientation of 2,6-azulene units is an effective strategy for obtaining high-performance organic optoelectronic materials.

2,6-Azulene-based Homopolymers: Design, Synthesis, and Application in Proton Exchange Membrane Fuel Cells.

Azulene-based homopolymers are of great interest from the point view of chemistry and material science. Herein, by means of Friedel-Crafts acylation to introduce solubilizing chains on the 1-position of azulene, we designed and synthesized two examples of 2,6-azulene-based homopolymers RP(Az-AC16) and P(Az-AC16). The arrangement of 2,6-azulene units is irregular for RP(Az-AC16), while P(Az-AC16) has head-to-head/tail-to-tail arranged 2,6-azulene units. Proton-responsive studies demonstrate that RP(Az-AC16) and P(Az-AC16) show reversible proton responsiveness in both solution and thin film. To utilize the dynamically reversible proton-responsive property of these polymers in thin films, RP(Az-AC16) and P(Az-AC16) were incorporated into a Nafion matrix as proton exchange membranes, wherein the Nafion/P(Az-AC16) composite membrane exhibits significant increases in proton conductivity relative to the Nafion membrane at different temperatures of each relative humidity (RH), which further results in a 64% improvement in hydrogen fuel cell output power under 30% RH at 80 °C. Our studies have realized the first solution synthesis of 2,6-azulene-based homopolymers and the first application of azulene-based π-systems in hydrogen fuel cells.

Electron-Deficient Contorted Polycyclic Aromatic Hydrocarbon via One-Pot Annulative π-Extension of Perylene Diimide.

The synthesis of a class of contorted electron-deficient polycyclic aromatic hydrocarbons (PAHs) has been achieved by a one-pot bay annulation of perylene diimide involving a mild Suzuki coupling and subsequent air-mediated, ambient-light-induced photocyclization. X-ray crystallography unambiguously confirmed the contorted PAH structure bearing four imide groups. The photophysical and electronic properties of these contorted PAHs were also analyzed, showing a high fluorescence quantum yield of 86% and moderate electron mobility of 0.017 cm2 V-1 s-1.

Dithieno[3,2-a:3',2'-j][5,6,11,12]chrysene diimides: a versatile electron-deficient building block for polymeric semiconductors.

In this work, dithieno[3,2-a:3',2'-j][5,6,11,12]chrysene diimides (DTCDI), an electron-deficient π-building block, were firstly incorporated into polymer main chains by using the 3,9-positions of chrysene and the α,α'-positions of thiophene units of DTCDI to connect with the 2,2'-bithiophene unit, affording copolymers P1 and P2, respectively. Due to their different connection ways the two polymers feature different optoelectronic properties.

Incorporation of 1,3-Free-2,6-Connected Azulene Units into the Backbone of Conjugated Polymers: Improving Proton Responsiveness and Electrical Conductivity.

Azulene as a potential building block for constructing organic/polymeric conjugated materials has attracted more and more attention due to its unique chemical structure and physicochemical properties. However, up to now, most reported azulene-based conjugated polymers have been dominated by the connection of the five-membered ring of azulene through 1,3-positions. Herein, by incorporating 1,3-free-2,6-connected azulene units into the polymeric backbone, two azulene-based all-carbon conjugated polymers P1 and P2 with different connection ways of 2,6-azulene and 2,7-fluorene units were presented. Protonation of these two polymers with trifluoroacetic acid leads to rapid and reversible color changes in both the solution and thin-film state. Moreover, these 1,3-free-2,6-connected azulene-based conjugated polymers exhibit high electrical conductivity (2.94 and 0.32 S/cm for P1 and P2, respectively) in thin film when doped by trifluoromethanesulfonic acid.

Incorporation of 2,6-Connected Azulene Units into the Backbone of Conjugated Polymers: Towards High-Performance Organic Optoelectronic Materials.

Azulene is a promising candidate for constructing optoelectronic materials. An effective strategy is presented to obtain high-performance conjugated polymers by incorporating 2,6-connected azulene units into the polymeric backbone, and two conjugated copolymers P(TBAzDI-TPD) and P(TBAzDI-TFB) were designed and synthesized based on this strategy. They are the first two examples for 2,6-connected azulene-based conjugated polymers and exhibit unipolar n-type transistor performance with an electron mobility of up to 0.42 cm2 V-1 s-1 , which is among the highest values for n-type polymeric semiconductors in bottom-gate top-contact organic field-effect transistors. Preliminary all-polymer solar cell devices with P(TBAzDI-TPD) as the electron acceptor and PTB7-Th as the electron donor display a power conversion efficiency of 1.82 %.

Furan Is Superior to Thiophene: A Furan-Cored AIEgen with Remarkable Chromism and OLED Performance.

Furan-cored AIEgen namely tetraphenylethylene-furan (TPE-F) is developed by diyne cyclization and its fluorescent and chemical properties are investigated and compared with its thiophene analogue. Results show that furan is superior to thiophene in terms of fluorescence, chromism, and charge transport. The mechanism of chromism of TPE-F is investigated and its efficient solid-state photoluminescence and good charge-transporting property enable it to serve as light-emitting material for the construction of electroluminescence devices with excellent performance. This work not only demonstrates an efficient strategy for constructing furan-cored AIEgens but also indicates that they are promising as advanced optoelectronic materials.

A Class of Electron-Transporting Vinylogous Tetrathiafulvalenes Constructed by the Dimerization of Core-Expanded Naphthalenediimides.

The combination of the (1,3-dithiol-2-ylidene)malononitrile (DTYM) and/or (1,3-dithiol-2-ylidene)acetonitrile (DTYA) moieties with naphthalenediimide (NDI) core affords two singly linked NDI-based dimers, (DTYM-NDI-DTYA)2 (D1) and (NDI-DTYA)2 (D2), which both contain a dicyano-substituted vinylogous tetrathiafulvalene (TTF) unit. The synthesis, thermal/optical/electrochemical properties of D1 and D2, and their primary applications in n-channel organic thin film transistors are studied. The results demonstrate that these NDI-fused vinylogous TTFs are excellent electron acceptors, and their further applications are promising.

Biazulene diimides: a new building block for organic electronic materials.

Azulene, a 10-π-electron isomer of naphthalene, is a nonbenzenoid bicyclic aromatic hydrocarbon with a beautiful blue color and a large dipole moment. We present here the first class of azulene-based aromatic diimides, 2,2'-biazulene-1,1',3,3'-tetracarboxylic diimides (BAzDIs), which comprise a 2,2'-biazulene moiety and two seven-membered imide groups. DFT calculations, thermal, optical and electrochemical properties of two BAzDI derivatives as well as single crystal analysis and the charge transport behavior were studied. The results demonstrate that BAzDIs have unique photophysical properties and are promising for organic electronic materials.

Shape-controllable and versatile synthesis of copper nanocrystals with amino acids as capping agents.

Thanks to their outstanding properties and a wide range of promising applications, the development of a versatile and convenient preparation method for metallic copper nanocrystals with controllable shape is of primary significance. Different from the literature that utilized a capping agent bearing only one kind of Cu binding functionality, either an amino or a carboxylic unit, for their preparation and shape control, this contribution reports a convenient method to engage both amino and carboxylic binding units at the same time. In this method, natural amino acids have been chosen as capping agents and demonstrated their versatile capabilities for the preparation of both Cu nanoparticles and nanowires. Detailed X-ray photoelectron spectroscopy revealed that the binding mode between amino acids and the Cu surface is highly dependent on their chemical structures. Interestingly, the produced Cu nanocrystals, exhibited an extraordinarily excellent anti-oxidation power. Furthermore, it was found that the multiple functionalities of amino acids not only have a great impact on the properties of their capped nanocrystals, such as solvent dispersibility, but also provide a convenient route for their further modification and functionalization.