Concise Synthesis of BN-Dibenzo[f,k]tetraphenes with Different BN Substitution Positions and Direct Comparison with Their Carbonaceous Analogue

BN-Acene Ladder with Enhanced Charge Transport for Organic Field-Effect Transistors

The in-depth research on the charge transport properties of BN-embedded polycyclic aromatic hydrocarbons (BN-PAHs) still lags far behind studies of their emitting properties. Herein, we report the successfully synthesis of novel ladder-type BN-PAHs (BCNL1 and BCNL2) featuring a highly ordered BC3N2 acene unit, achieved via a nitrogen-directed tandem C-H borylation. Single-crystal X-ray diffraction analysis unambiguously revealed their unique and compact herringbone packing structures. Micro-sized single-crystalline organic field-effect transistors (OFETs) demonstrated that an enhanced charge transport capability, with BCNL2 achieving a hole mobility of up to 0.62 cm2 V-1 s-1-three orders of magnitude higher than that of BCNL1 (μh max=6 × 10-4 cm2 V-1 s-1), ranking among the highest values for BN-PAHs-based OFETs. Detailed calculations attribute this significant enhancement in the hole mobility to the marked reduction in reorganization energy (λ) of BCNL2, resulting from the five-membered pyrrole ring annulation and molecular skeleton elongation. This work provides insight into molecular design principles for potential BN-PAHs in optoelectronic applications.

Heterocoronenes Containing Pyridine and 1,2-Azaborine Units

Several coronenes containing pyridine and azaborine units have been readily prepared and structurally confirmed by X-ray crystallographic analysis. The codoping results in interesting findings and properties such as the first observation of BN-H---NPy hydrogen bonds in crystals of BN-PAHs, short π-π stacking distances, lowered HOMO-LUMO levels, narrow band gap, and unique dual response to fluoride ion and proton in solution.

Assessing the Role of BN-Embedding Position in B2N2-Perylenes

Incorporating heteroatoms can effectively modulate the molecular optoelectronic properties. However, the fundamental understanding of BN doping effects in BN-embedded polycyclic aromatic hydrocarbons (PAHs) is underexplored, lacking rational guidelines to modulate the electronic structures through BN units for advanced materials. Herein, a concise synthesis of novel B2N2-perylenes with BN doped at the bay area is achieved to systematically explore the doping effect of BN position on the photophysical properties of PAHs. The shift of BN position in B2N2-perylenes alters the π electron conjugation, aromaticity and molecular rigidness significantly, achieving substantially higher electron transition abilities than those with BN doped in the nodal plane. It is further clarified that BN position dominates the photophysical properties over BN orientation. The revealed guideline here may apply generally to novel BN-PAHs, and aid the advancement of BN-PAHs with highly-emissive performance.