ABSTRACT The investigation of ion–molecule reactions in mass spectrometers (i.e., bond formation between a reactive gaseous ion and a neutral reagent) is a well‐established method for analyzing fundamental ion reactivity. However, the potential of such reactions to generate new ions used in preparative mass spectrometry has only recently come into focus. This concept article highlights the dual significance of ion–molecule reaction products in preparative mass spectrometry: First, they provide valuable insights into the intrinsic reactivity and selectivity of reactive ions in the gas phase, forming the foundation of their reactions at molecular interfaces during ion deposition. Second, the gaseous products themselves can be deposited as mass‐selected building blocks for synthesizing thin films and functional materials. Herein, we discuss opportunities and challenges involved in translating knowledge from the gas‐phase chemistry of reactive ions to interface reactivity. This includes considerations such as the comparability of reaction partners, changes in the nature of ions upon deposition, the emergence of new reaction pathways in condensed phases, and orientation effects at interfaces. A mechanistic understanding of the gas‐phase reactions of reactive ions, as well as the mass‐selected deposition of their products, is opening up new possibilities in surface functionalization and thin‐layer synthesis.
Rohdenburg et al. (2026) studied this question.