Gas-phase synthesis and soft-landing deposition of imidazole clusters with narrowband emission

Imidazole and its derivatives are common in bioactive molecules and function as pharmacophores in diverse medications. This study examines the gas-phase reactions of imidazole and benzylimidazole using a self-developed reflectron time-of-flight mass spectrometer equipped with dual sources and a downstream tube reactor. It was found that the Cu⁺/Ag⁺ ions readily coordinate with these organic molecules to create metal complexes; furthermore, the plasma-assisted Cu⁺/Ag⁺ ions enable C–N coupling reactions to generate a C₁₇H₁₇N₂^+· radical assigned to 1,3-dibenzylimidazole, along with hydropolymerization to form molecular clusters through hydrogen bond linkers. With Im₃H⁺ as a representative, we attained soft-landing deposition and measured its fluorescence. Interestingly, the deposited quantum dots of Im₃H⁺ clusters exhibit narrow-width emission at 516 nm, which fits well with the time-dependent density functional theory (TD-DFT) calculation results. Through DFT calculations, we also elucidated the chemical interactions in these cluster systems. This study advances the basic understanding of heteroaromatic compounds and their weakly bound clusters, and provides a solvent-free synthesis technique for organic molecular clusters and metal-organic complexes.