Synthesis and Properties of B4N4‐Heteropentalenes Fused with Polycyclic Hydrocarbons

Abstract

AbstractHybrid molecules of π‐conjugated carbon rings and BN‐heterocyclic rings (h‐CBNs) fused with each other have been a rare class of compounds due to the limited availability of their synthetic methods. Here we report the synthesis of new h‐CBNs featuring a B4N4‐heteropentalene core and polycyclic aromatic hydrocarbon wings. Using 1,2‐azaborinine derivatives as a building block, we developed a rational synthetic protocol that allows the formation of a B4N4 ring in a stepwise manner, resulting in the fully fused ABA‐type triblock molecules. Thus, three derivatives of 1 bearing naphthalene (1Naph), anthracene (1Anth), or phenanthrene (1Phen) wings fused with the B4N4 core were synthesized and characterized. Among them, 1Phen, which displays the highest triplet‐state energy, was found to serve a host material for phosphorescent OLED devices, for which a maximum external quantum efficiency of 13.7 % was recorded. These findings may promote the synthesis of various types of h‐CBNs aiming at new properties arising from the synergy of two different π‐electronic systems.