Size-dependent stability and intracluster reactions have been investigated by photoionization mass spectrometry for alkali metal (M; Li, Na, and K)-methyl propiolate (MP; HC≡CCOOCH3) molecules clusters. In the photoionization mass spectra, the intensities of M+(MP)3 ions (M=Na and K) were unexpectedly high, whereas no intensity anomaly was observed in Li+(MP)n mass spectrum. The intensity anomaly can be explained by intracluster cyclization reaction induced by electron transfer from the metal atom and resulting a stable benzene derivative formation. Ion intensities of M+(MP)n(H2O) relative to M+(MP)n have a minimum at n=3 in Na and K systems. This result is owing to evaporation of water and/or MP molecules following exothermic cyclization reaction. Fragment ions with a loss of CH 2 were also observed predominantly from M(MP)2 in all metal systems. These ions are expected to be produced by hydrolysis in M(MP)n(H2O) clusters producing a HC≡CCOOH molecule. The difference between lithium and other alkali metals is due to the rigidity of clusters with respect to deformation into geometry leading to the polymerization reaction.
- Alkali metal
- Intracluster reaction
ASJC Scopus subject areas
- Condensed Matter Physics
- Physical and Theoretical Chemistry