In this project of the Hector Fellows A. Stephen K. Hashmi and Manfred Kappes the postdocs Dr. Sarah Bay (Univer­sity of Heidel­berg) and Dr. Jean-Francois Greisch (Karlsruhe Insti­tute of Technol­ogy) are involved. They examine the charac­ter­is­tics of innov­a­tive gold catalysts.

The figure shows the workhorse, a dual activa­tion catalyst. Direct activ­ity assess­ment includ­ing the influ­ence of byprod­ucts (e.g. small clusters of various charge states) as well as the identi­fi­ca­tion of reaction inter­me­di­ates has been missing, which finally prevented efficient optimiza­tion. Since concen­tra­tions of the new highly active gold catalysts are typically low and the active species are fragile, charac­ter­i­za­tion using analytic techniques is challenging.

Never­the­less, the combi­na­tion of high-resolu­tion mass spectrom­e­try and mild ioniza­tion methods provided a unique oppor­tu­nity to directly probe catalyst-substrate-inter­me­di­ates using a broad range of spectro­scopic techniques.

Via ion mobil­ity measure­ments, colli­sion cross-sections could be inferred and struc­tural infor­ma­tion on the isolated inter­me­di­ates of reactions obtained. Reaction of gas-phase species with vapors could provide unique infor­ma­tion on the reactiv­ity, making it possi­ble to assess how differ­ent isomers/conformers contribute to the reaction. Finally, optical spectro­scopic techniques could be used to probe the struc­ture and the electronic states as well as to isolate species for further inves­ti­ga­tion via hole-burning spectroscopy.

By analyz­ing the reaction mixture and devel­op­ing new approaches to access­ing transient species, the project aimed at obtain­ing unprece­dented infor­ma­tion on the mecha­nisms and species involved in gold-catalyzed reactions.