A Layered Two‐Dimensional Hydrogen‐Bonded Organic Framework Based on 2,5,8,11‐Tetrakis(4‐Carboxyphenyl)Perylene Diimide: Structural Nature, Optical and Photophysical Properties

ABSTRACT Perylene diimide (PDI) derivatives exhibit outstanding optical and electronic properties, making them a versatile material for photonic applications. Herein, we report on the synthesis and spectroscopic characterization of a novel PDI‐based hydrogen‐bonded organic framework (HOF, CP‐PDI‐1(DCB) ) and related compounds. The HOF assembles into a layered 2D network with slip‐stacked AB packing mediated by CH···π interactions. The absorption and emission spectra of the studied PDI derivatives in solid state, as well as in polymethyl methacrylate (PMMA) matrices, exhibit monomers, aggregates and excimer contribution. Upon solvent removal, CP‐PDI‐1 shows a red‐shifted emission and an enhanced excimer signal, evidencing that structural reorganization affects its photobehavior. Time‐resolved experiments of CP‐PDI‐1 reveal the coexistence of monomer species (0.32 ns) and H‐type aggregates (0.04 ns) that act as precursors to excimer‐like species (5.60 ns). Additionally, the crystal structure of CP‐PDI‐1 promotes the formation of emissive J‐type aggregates (1.65 ns). While excimer formation occurs slowly in PDI‐boron (220 ps) and CP‐PDI‐ester (130 ps) due to steric hindrance, in unsubstituted PDI and CP‐PDI‐1 it takes place in less than 20 ps (in solid state) and 10 ps in suspension. These findings provide key information for the design of advanced PDI‐based optical materials.