Yubin Fu

Ladder-Type BN-Embedded Heteroacenes with Blue Emission

Using a concise synthetic strategy, a series of novel ladder-type BN-embedded heteroacenes were successfully synthesized. Their molecular skeletons render the versatile modification which is desirable for achieving unique physical properties. Organic light-emitting diode devices based on BN-embedded heteroacenes were subsequently fabricated, demonstrating their promising application as blue emitters.

Synthesis of NBN-Type Zigzag-Edged Polycyclic Aromatic Hydrocarbons: 1,9-Diaza-9a-boraphenalene as a Structural Motif

A novel class of dibenzo-fused 1,9-diaza-9a-boraphenalenes featuring zigzag edges with a nitrogen-boron-nitrogen bonding pattern named NBN-dibenzophenalenes (NBN-DBPs) has been synthesized. Alternating nitrogen and boron atoms impart high chemical stability to these zigzag-edged polycyclic aromatic hydrocarbons (PAHs), and this motif even allows for postsynthetic modifications, as demonstrated here through electrophilic bromination and subsequent palladium-catalyzed cross-coupling reactions. Upon oxidation, as a typical example, NBN-DBP 5a was nearly quantitatively converted to σ-dimer 5a-2 through an open-shell intermediate, as indicated by UV-vis-NIR absorption spectroscopy and electron paramagnetic resonance spectroscopy corroborated by spectroscopic calculations, as well as 2D NMR spectra analyses. In situ spectroelectrochemistry was used to confirm the formation process of the dimer radical cation 5a-2(•+). Finally, the developed new synthetic strategy could also be applied to obtain π-extended NBN-dibenzoheptazethrene (NBN-DBHZ), representing an efficient pathway toward NBN-doped zigzag-edged graphene nanoribbons.

A Stable Saddle-Shaped Polycyclic Hydrocarbon with an Open-Shell Singlet Ground State

Diindeno-fused bischrysene, a new diindeno-based polycyclic hydrocarbon (PH), was synthesized and characterized. It was elucidated in detailed experimental and theoretical studies that this cyclopenta-fused PH possesses an open-shell singlet biradical structure in the ground state and exhibits high stability under ambient conditions (t1/2 =39 days). The crystal structure unambiguously shows a novel saddle-shaped π-conjugated carbon skeleton due to the steric hindrance of the central cove-edged bischrysene unit. UV/Vis spectral measurements revealed that the title molecule has a very narrow optical energy gap of 0.92 eV, which is consistent with the electrochemical analysis and further supported by density functional theory (DFT) calculations.

Efficient approach to electron-deficient 1,2,7,8-tetraazaperylene derivatives.

Using an efficient synthetic strategy, a novel class of 1,2-diazine-embedded perylenes, namely 1,2,7,8-tetraazaperylene derivatives, have been successfully synthesized. These molecules were fully characterized by X-ray diffraction analysis, optical spectroscopy, and electrochemistry. The low-lying lowest unoccupied molecular orbital (LUMO) level of these molecules suggests their potential as good electronic acceptors.

Synthesis and Properties of C2h-Symmetric BN-Heteroacenes Tailored through Aromatic Central Cores

The 2-fold successive electrophilic borylation on one aromatic central core led to a series of C(2h)-symmetric BN-heteroacenes in excellent yields. For the first time, we introduced trimethylsilyl (TMS) as either leaving group or oriented group for efficiently improving the preparation of BN-embedded polycyclic aromatic hydrocarbons (PAHs). The physical properties of the as-synthesized BN-heteroacenes in either solid state or solution can be finely tuned through the position isomerization or the fused ring numbers of the aromatic central core.

Angular BN-Heteroacenes with syn-Structure-Induced Promising Properties as Host Materials of Blue Organic Light-Emitting Diodes

A series of novel angular BN-heteroacenes were successfully synthesized. Associated with the intrinsic syn-structures, they exhibit unique molecular alignments in a solid state and promising electronic properties, and are thus suitable as efficient nondoped emitters for the fabrication of blue organic light-emitting diodes with improved performance.

Cationic Nitrogen-Doped Helical Nanographenes

Herein, we report the design and synthesis of a series of novel cationic nitrogen-doped nanographenes (CNDNs) with nonplanar geometry and axial chirality. Single-crystal X-ray analysis reveals helical and cove-edged structures. Compared to their all-carbon analogues, the frontier orbitals of the CNDNs are energetically lower lying, with a reduced optical energy gap and greater electron-accepting behavior. Cyclic voltammetry shows all the derivatives to undergo quasireversible reductions. In situ spectroelectrochemical studies prove that, depending on the number of nitrogen dopants, either neutral radicals (one nitrogen dopant) or radical cations (two nitrogen dopants) are formed upon reduction. The concept of cationic nitrogen doping and introducing helicity into nanographenes paves the way for the design and synthesis of expanded nanographenes or even graphene nanoribbons with cationic nitrogen dopants.

Triple Boron-Cored Chromophores Bearing Discotic 5,11,17-Triazatrinaphthylene-Based Ligands

A series of novel chromophores fused with multiple boron cores have been successfully synthesized by the complexation of three difluoroboryl or diphenylboryl at the periphery of 5,11,17-triazatrinaphthylene derivative ligands. Their sterically congested molecular scaffolds with expanded π-conjugated discotic backbones render them with unique electronic properties including large Stokes shifts, tunable electrochemical behaviors, and low-lying LUMO energy levels up to -3.18 eV.

Toward Full Zigzag-Edged Nanographenes: peri-Tetracene and Its Corresponding Circumanthracene

Zigzag-edged nanographene with two rows of fused linear acenes, called as n- peri-acene (n-PA), is considered as a potential building unit in the arena of organic electronics. n-PAs with four ( peri-tetracene, 4-PA), five ( peri-pentacene, 5-PA) or more benzene rings in a row have been predicted to show open-shell character, which would be attractive for the development of unprecedented molecular spintronics. However, solution-based synthesis of open-shell n-PA has thus far not been successful because of the poor chemical stability. Herein we demonstrated the synthesis and characterization of the hitherto unknown 4-PA by a rational strategy in which steric protection of the zigzag edges playing a pivotal role. The obtained 4-PA possesses a singlet biradical character ( y0 = 72%) and exhibits remarkable persistent stability with a half-life time ( t1/2) of ∼3 h under ambient conditions. UV-vis-NIR and electrochemical measurements reveal a narrow optical/electrochemical energy gap (1.11 eV) for 4-PA. Moreover, the bay regions of 4-PA enable the efficient 2-fold Diels-Alder reaction, yielding a novel full zigzag-edged circumanthracene.