Hydrogen-Bond Topology Governs Clustering-Triggered Emission in Non-Conjugated Small Molecules

We report hydrogen bond-assisted clustering-triggered emission (CTE) mechanism in a systematic 2 × 3 set of six simple, nonconjugated molecules that vary in functional group (diamine, amino alcohol, diol) and chain length (C2 vs C3). Fluorescence intensities follow clear structural trends: diamine > amino alcohol > diol, and C3 > C2, with 1,3-diaminopropane exhibiting the strongest emission. Spectroscopy combined with molecular dynamics simulations reveals that these differences are governed by liquid-phase hydrogen-bond topology and the resulting balance between exciton migration and exciton confinement. Specifically, diols preferentially form continuous, percolated O-H···O networks that facilitate long-range energy migration and increase access to nonradiative quenching pathways. In contrast, diamines and longer-chain analogues favor fragmented association and discrete clustering, which is consistent with exciton confinement and enhanced radiative decay. These findings suggest a topology-driven design principle for nonconjugated luminogens, in which structural flexibility and discrete clustering promote bright CTE without reliance on π-conjugation.