Xiao-Ye Wang

BN Heterosuperbenzenes: Synthesis and Properties

Replacement of C=C unit with its isoelectronic B-N unit in aromatics provides a new class of molecules with appealing properties, which have attracted great attention recently. In this Concept, we focus on BN-substituted polycyclic aromatics with fused structures, and review their synthesis, photophysical, and redox properties, as well as their applications in organic electronics. We also present challenging synthetic targets, large BN- substituted polycyclic aromatics, such as regioregular BN heterosuperbenzenes, which can be viewed as BN-doped nanographenes. Finally, we propose an atomically precise bottom-up synthesis of structurally well-defined BN-doped graphenes.

Azaborine Compounds for Organic Field‐Effect Transistors: Efficient Synthesis, Remarkable Stability, and BN Dipole Interactions

Organic semiconductors have attracted great attention during the past few decades for the development of next-generation electronics. The incorporation of a B N unit, which is isoelectronic to the C=C moiety, into p systems provides a novel approach in the molecular engineering of organic semiconductors. BN substitution can change the electronic properties of p systems, and afford additional intermolecular dipole–dipole interactions. Therefore, BN-incorporated semiconductors provide new opportunities for organic electronics. Although significant progress has been made in azaborine chemistry, the construction of azaborine rings in large p scaffolds remains challenging. Moreover, azaborine compounds are usually susceptible to moisture and oxygen, and their thermal decomposition temperatures are around 200 8C, thus limiting their promising applications as organic materials. As a result, the charge-transport properties of azaborine compounds have rarely been investigated up to now. Only recently, Nakamura and co-workers reported a BN-fused polycyclic aromatic compound which exhibited higher intrinsic hole mobility than its carbon analog by timeresolved microwave conductivity measurements, implying that BN-substituted aromatics might outperform their carbon analogs in organic electronics. Nonetheless, electronic devices based on azaborine compounds have not yet been demonstrated. Herein, we synthesize two novel BN-substituted tetrathienonaphthalene derivatives BN-TTN-C3 and BN-TTN-C6 through an efficient one-pot electrophilic borylation method (Scheme 1). Four thiophene rings are fused onto a BNsubstituted naphthalene core to extend the p conjugated plane for intermolecular p–p stacking and charge-carrier

A straightforward strategy toward large BN-embedded π-systems: Synthesis, structure, and optoelectronic properties of extended BN heterosuperbenzenes

A straightforward strategy has been used to construct large BN-embedded π-systems simply from azaacenes. BN heterosuperbenzene derivatives, the largest BN heteroaromatics to date, have been synthesized in three steps. The molecules exhibit curved π-surfaces, showing two different conformations which are self-organized into a sandwich structure and further packed into a π-stacking column. The assembled microribbons exhibit good charge transport properties and photoconductivity, representing an important step toward the optoelectronic applications of BN-embedded aromatics.

Non-fullerene acceptors containing fluoranthene-fused imides for solution-processed inverted organic solar cells

Six fluoranthene-fused imide derivatives were employed as acceptors in solution processed inverted BHJ solar cells with P3HT as the donor. The PCEs of all devices vary from 2.14% to 2.89%. All acceptors are in their amorphous state with low electron mobility, but achieving high PCEs.

B2N2-Dibenzo[a,e]pentalenes: Effect of the BN Orientation Pattern on Antiaromaticity and Optoelectronic Properties

Two BN units were embedded in dibenzo[a,e]pentalene with different orientation patterns, which significantly modulated its antiaromaticity and optoelectronic properties. Importantly, the vital role of the BN orientation in conjugated molecules with more than one BN unit was demonstrated for the first time. This work indicates a large potential of the BN/CC isosterism for the development of new antiaromatic systems and highlights the importance of precise control of the BN substitution patterns in conjugated materials.

A bowl-shaped molecule for organic field-effect transistors: crystal engineering and charge transport switching by oxygen doping

A corannulene-based derivative was facilely developed with a bowl-shaped structure. Highly ordered cofacial convex–concave stacking was realized through tuning the molecular dipoles, which is favorable for charge transport. Organic field-effect transistors were fabricated, providing opportunities for a broad class of corannulene derivatives and buckybowl aromatics for application in future organic electronic devices.

Influence of alkyl chain length on the solid-state properties and transistor performance of BN-substituted tetrathienonaphthalenes

Flexible side chains have not drawn much attention in the development of organic semiconductors compared to the conjugated backbone counterparts. In this work, a series of BN-substituted tetrathienonaphthalenes (BN-TTNs) with methyl to hexyl side chains were synthesized to systematically investigate the influence of alkyl chain length on the solid-state properties and transistor performance. The intrinsic electronic properties of the π-conjugated backbone were not affected by different alkyl chains, but the solid-state properties, such as molecular packing structures, energy levels, thin-film morphologies, and transistor performance, were significantly influenced. Among the six compounds, BN-TTN-C3 exhibited the highest hole mobility of 0.15 cm2 V−1 s−1, whereas BN-TTN-C2 and BN-TTN-C4 did not show any field-effect mobility. This unprecedented difference of device performance was mainly caused by different thin-film morphologies. An odd–even effect of alkyl side chains on the thin-film morphology was observed for the first time, which further greatly influenced the device performance. This pronounced influence of alkyl chain length on the device performance indicates that alkyl chains play a vital role in organic electronics and should be paid more attention in future development of organic semiconductors.

Intramolecular C–F and C–H bond cleavage promoted by butadienyl heavy Grignard reagents

Organomagnesium compounds (Grignard reagents) are among the most useful organometallic reagents and have greatly accelerated the advancement of synthetic chemistry and related sciences. Nevertheless, heavy Grignard reagents based on the metals calcium, strontium or barium are not widely used, mainly due to their rather inert heavy alkaline-earth metals and extremely high reactivity of their corresponding Grignard-type reagents. Here we report the generation and reaction chemistry of butadienyl heavy Grignard reagents whose extremely high reactivity is successfully tamed. Facile synthesis of perfluoro-π-extended pentalene and naphthalene derivatives is realized by the in situ generated heavy Grignard reagents via intramolecular C-F/C-H bond cleavage. These obtained perfluorodibenzopentalene and perfluorodinaphthopentalene derivatives show low-lying LUMO levels, with one being the lowest value so far among all pentalene derivatives. Our results set an exciting example for the meaningful synthetic application of heavy Grignard reagents.

Benzo‐Fused Double [7]Carbohelicene: Synthesis, Structures, and Physicochemical Properties

A benzo-fused double [7]carbohelicene (D7H) was synthesized through a regioselective cyclodehydrogenation of a tetranaphthyl-p-terphenyl-based precursor. The twisted (D7H-1) and anti-folded (D7H-2) conformers of D7H were separated by recrystallization, and their double helicene structures with overlapping terminal benzene rings were unambiguously elucidated by X-ray crystallography. A record-high isomerization barrier (46.0 kcal mol-1 ) in double helicenes was estimated based on density functional theory (DFT) calculation, which resulted in the excellent conformational stability of D7H. The physicochemical properties of D7H-1 and D7H-2 were investigated by UV/Vis absorption spectroscopy and cyclic voltammetry, displaying the variation of electronic structure upon conformational changes. The optical resolution of the racemic D7H-1 was carried out by chiral HPLC, offering enantiopure D7H-1-(P,P) and D7H-1-(M,M), which were further characterized by circular dichroism spectroscopy.

Fusion at the non-K-region of pyrene: an alternative strategy to extend the π-conjugated plane of pyrene.

A large fused pyrene derivative TTTP was facilely developed through fusion at the non-K-region of pyrene, which represents the first example of extending such a π-conjugated plane at its non-K-region. The investigation of its photophysical properties and other characterizations indicated that TTTP exhibited strong aggregation behaviors and self-assembled into highly ordered one-dimensional nanowires due to its large π-conjugated plane.