Activating Electronic Delocalization: Through-Space Lone-Pair Interactions versus Hydrogen Bonding

Abstract

It is still unclear how weak interactions specifically affect electronic structures. Here, we systematically reduce the number of N–H bonds within diarylmethane (DAM), precisely diminishing the number of hydrogen bonds (H-bonds). Contrary to the widely reported result that H-bonds could enhance molecular brightness by promoting electron delocalization, DAMs lacking H-bonds exhibit superior luminescence, compared to DAMs with H-bonds in both dilute solutions and solid states. It is indicated that H-bonds tend to induce n-electron localization, preventing the formation of through-space lone-pair conjugation (n–n TSC). In addition, unlike the widely studied through-space π–π conjugation that only existed in the aggregate state, the n–n TSC can even stabilize the conformation and is expressed in dilute solutions. Herein, we not only achieve bright white-light emissions in nonconjugated small molecules but also reveal the surprisingly competitive relationship between H-bonds and n–n TSC in electronic delocalization, providing a new strategy for designing excellent optoelectronic materials via the n-electron bridge.