A Molecular Descriptor for Characterizing the Strength of Through-Space Conjugation for Luminescent Property in Organic Materials

Noncovalent through-space conjugation (TSC), a unique property of π-charge delocalization, has emerged as a powerful strategy for modulating the optoelectronic properties of organic materials. However, the quantitative relationship among the molecular structure, the strength of TSC, and optoelectronic properties has not yet been established. Here, using typical conjugated aromatic compounds as model systems, it is revealed that TSC arises from the interaction of π-orbitals, and a molecular descriptor, composed of geometric parameters, is proposed to characterize the strength of TSC. This descriptor exhibits a strong linear correlation with the orbital splitting energy of symmetric and antisymmetric π-orbitals, achieving a linear fit coefficient (R2) as high as 0.935. More importantly, A shows a strong positive correlation with the spectral red-shift of organic materials, suggesting that TSC can effectively tune the luminescent properties of organic materials. The descriptor is helpful for the rational design and machine-learning-based high-throughput screening of advanced organic luminescent materials.