BN/BO Doping of <i>peri</i> ‐Acenoacenes: Modulating Excited States in Trapeziumene Congeners

Abstract The rational design of polycyclic aromatic hydrocarbons that combine chemical and physical robustness with finely tuned optoelectronic properties remains a key challenge in materials science. As an initial step toward this goal, we report the synthesis and comprehensive characterization of a new class of boron‐, nitrogen‐, and oxygen‐doped peri ‐acenoacenes, termed (2,5,4)‐trapeziumene congeners. Analysis of these systems provides chemical descriptors that could guide the rational tailoring of their properties through peripheral doping. The target trapeziumene congeners were obtained via a sequence of Suzuki–Miyaura and Buchwald–Hartwig couplings, followed by directed borylation, giving both phenylborane and borinic derivatives with diverse peripheral doping sequences. Single‐crystal X‐ray diffraction revealed planar to slightly twisted backbones, with peripheral heteroatomic motifs that modulate π‐conjugation and intermolecular packing. Photophysical studies showed bright fluorescence ( Φ F up to 0.99), narrow Stokes shifts, and structured phosphorescence at 77 K. Electrochemical analysis demonstrated p‐type behavior and a progressive HOMO–LUMO gap widening upon N→O substitution. Theoretical investigations revealed that N→O substitution asymmetrically affects the excited states, blue‐shifting fluorescence while red‐shifting phosphorescence, through an asymmetric charge stabilization in the S 1 and T 1 excited states. This is accompanied by a progressive widening of the T 1 –T 2 energy gap.